Welcome to the first in a series of stories relating to famous diesel engines of the past and present. I can’t think of a better one to start with than the Detroit Diesel Series 71. The story begins back in 1938 when GM subsidary Detroit Diesel unvieled thier first product, the two stroke, inline 6 cylinder 6-71. The inline models were offered in a one, two, three, four and six cylinder variants. In 1957 V-block versions were introduced and would eventually included 6,8,12,16,24 configurations. At first glance the naming convention seems cryptic but is rather straight forward when you think about it. For example, the 6-71. The six stands for the number of cylinders, the 71 stands for the cubic displacement of each cylinder. The 12V71 is a 12 cylinder in a V-block setup. To continue the code a T would stand for turbo charged. L or N would stand for low profile, a setup commonly used in buses. The larger of the 71 series in a V-Block configuration were usually two of the smaller setups married together our used the same set of heads allowing parts to be easily swapped. The applications of the 71 series were limitless. 6V-71 were common with bus and coach builders. 8V-71 were popular with firetruck manufactures, it is pretty difficult to find an old fire truck without an Detroit under the hood or cab. But to really appreciated a Detroit you have to hear it, they truly have a sound all their own. So, on to the videos.
6-71 – 190 HP
12V71 – 450 HP
8V-71 – 318 HP
I hope you enjoyed my novice homage to this great and long lived engine. Despite their unfailing ability to constantly leak oil you will still find fans of the 71 all across the globe. Please feel free to correct or and any relevant information by emailing eric@dailydieseldose.com or just leave a comment below. If you have a candidate for the next KYD story let me know!
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In my mind one of the best engines every made. Not the most powerful, but what other engine has lastest the test of time like this one.
Love those Rocky Mountain Hummingbirds!
Hard to argue that. No other engine sounds the same. Music to my ears.
Nothing better than the sound of an in-line 6-71! Have you covered the electromotive divisions 567 yet? Or the 645? for those who don’t know already, there’s actually a very interesting paper written by Eugene kettering, about the history and development of the EMd 567 series general motors locomotive engine.
Damn straight best reliable ive had pleasure of owing 2 boats with 8v71 ieasy peasy to work on!! Looking to buy an old yacht with 2 8v71s ive been waiting for this opportunity i would gave no other
my question,I have a 6v71 lh rotation eng I am a mechanic too and want to change it to rh I know how to do this but am wondering if the cam shafts are the same
The cams are different between the lh aha rh versions. If you ever tried to stop one of these engines by stalling it you know they will run in reverse, but the power isn’t right, you have to change the camshaft.
When you run them in reverse smoke comes out the air cleaner.. I saw my buddy stall his dump truck then it rolled forward in reverse He pulled in the clutch and it was still running but the dump box would not go up .. If I can recall I put my hand over the exhaust pipe and and it was sucking air in through the exhaust pipe ..
I was told by a mechanic that the same camshaft was used for either rotation; it had to be removed and turned end for end. Not the same for the starter, you will need one with the correct rotation.
I had a Detroit in a loader and had to swap engines because the engine went bad. I ordered a military engine from boats and harbors with an opposite rotation. All I had to do was in bolt everything from the block and rebolt it on the other side of the block and reinstall the engine. In other words just turn the block around. The engine is symetical, so it all bolts back up when the block is turned around.
No they are not the same there are RH and LH camshafts
The block of a Detroit is exactly alike on both sides and ends. To reverse rotation, just unbolt everything, turn the block end for end, and bolt everything back onto the block. I did it, and I know that it works! No changing cams or anything else internally! End of story!
Yes they are but if.the engine has.advanced.cam timing you need to change that,no bigdeal.just change it by one tooth in opposite direction
You should be a part of a contest for one of the most useful blogs on the internet.
I am going to recommend this blog!
Before GM made Detroit Diesels in V configuration, they married two or four 6-71’s together in”twin” or “quad” installations. I remember seeing two quad installations in the engine room of an ex US Navy inshore minesweeper. Imagine the glorious howl of two 24 cylinder powerplants at full throttle. Makes my spine shiver! I worked on boats with 6-71 and 4-71 engines. No matter how many cylinders, they all sounded the same to me, a nice throaty rumble at idling speed that became a uniquely soul stirring scream at 1800 rpm. Wonderful.
You certainly did not walk around anywhere near the air intake with an oilers rag in your pocket.
I sniped a bunch of LCVPs, Mike6 boats, and Captain’s Gigs as an engineman in the U.S. Navy from 1973-1977. Motor Whale Boats too (Perkins powered). I became really proficient at trouble shooting and rebuilding Jimmies. It was my passion at the time. I used to rebuild and pop test the injectors as well. In addition, I also operated, maintained, and took part in rebuilding one of our Fairbanks-Morse emergency generators aboard USS Coronado LPD-11. Later in life I used to drive a 238 powered White 4000 single axle tractor with a 10 sp. Roadranger pulling tank trailers. Love the Detroit 2 cycle sound! By the way…the are made to run up to 2,100 rpm. Typical operation. Thanks for the memories!
Owen F McCaffrey….. “By the way…the are made to run up to 2,100 rpm.”….. just so you know, the series 71 engines “can” be taken up to well over 3,000 rpms.
We ran the v12 in the Kenworth that we ran in the Pro Semi Class of Sled Pulling at up to 4,200 rpm and never blew it up, in nearly 32 years of pulling, though did spin a bearing once.
I’m looking at a 1947 GMC siverside bus been setting probly 15 + years what will I be in for love them dd thanks Vic
Hello Vic, So Sorry for Not responding back to your reply and question from July 2019… 5.5 Years ago!! I Never received any notice that I had gotten a response or question from anyone.
I just happened back on this site a few minutes ago and found your question to me. Did you ever get that GM Silverside, that you were looking at?? I will keep an eye on this site… to see if you might happen to reply back again. Again, my sincere apology.
Vic… PS; I just posted a reply to you… today is Jan.25th, 2025.
I’m looking at a 1947 GMC siverside bus been setting probly 15 + years what will I be in for love them dd 671s also have a 6v92 bus thanks Vic
I worked on a surface mine in Martin co Ky in 1974 through 1985 I think the mine worked 25or 30 unit rigs the 175 toners had 16cylinders that powered the electric turbines I always liked to hear them dumps load of rock they you could hear for miles
Further to my previous comment, I remember a pair of “handed” Gray Marine 6-71 engines, with Twin Disc marine gearboxes (Allison Division of GM) that had been taken from a landing craft, so they had been built during WW II. They still had their brass plates on the flywheel housing with the official number issued by the US Bureau of Ships. They had the larger injectors, and when the boat was fresh out of refit, they could push her along pretty smartly. We used to run up to 1500 rpm, but could push 1750 if needed. The biggest trouble was keeping the seawater cooling system clear of weed and mud which could cause overheating. The boat was eventually scrapped, but I don’t know if the jimmies survived.
Unless someone was foolish enough to junk them I bet they are still running!
That’s so true Roy. As I remember (it was many years ago) you had a sea water strainer before the keel cooler you had to keep clear. The Jabsco pump did not like to run dry. We used to pack the rubber impeller with grease to lubricate them until they picked up salt water. It was just a half-dozen Phillip’s head screws to get the cover off. I would do it again! Sometimes the bosun’s mates would let me drive the boat (Mike 6 or LCVPs) I got pretty good at it! I even landed 80 or so drunk Marines up against the ship. They all were laughing and taunting me. I made a smooth docking. We used to cook misappropriated Marine C-rats on the exhaust manifolds. I even steered an LCVP drive by of a Russian cruiser off Cypress one time! All done with Gray Marines. Good times.
Roy Kennedy….. “We used to run up to 1500 rpm, but could push 1750 if needed.” It’s a wonder those poor engines survived at such low rpms…. None of my Detroits ever saw less than 1900 once under way…. with the governors set for 2,850 rpms… loaded.
Most all “pleasure craft” detroits came from the factory set at 2,350 for the Series 71 engines. In the Pro “Sled Pulls” for Pro-Semi Class, we turned the V12 (71 series) at 4,100 to 4,200 under full load for years, and never blew it up.
Wow thats crazy i knew a guy who had a v12 71 series in a kw long nose tractor he had his turned up to 3200 rpm he told.me he used higher strenth valve springs though !I rebuilt a v8_71 for my brouther used 71 brn tag injectors set gov.to 2650 rpm it ran real decent for a detroiter but at 3_4 mpg wasant going to win any milage contests it ranfor 150 thousand miles then the damned air compressor went out sending little pieces of compressor parts into the intake tube this took out the blower sending more junk into the pistons what a piss poor way of getting air for the compressor!it was rebiult agian but not by me the owner who had purchased it from my brouther took my advice and used an old lawn tractor air filter and a seperate air tube for the compresseor!I saw that truck on the road for around four more years zfter that the guy told me he put in all new bearings pistons ect but lefht ghe settings alone! Back in thier time they made trckers money!as a final thought i think detroit made the only v8 diesel that held up.
Mike,
I know I didn’t mention it in my post above, but no… you cannot run the “stock” springs at much over 2450/2500 rpm or you will run the risk of valve float. We used a modified set of springs used in Pro Stock drag race engines…. as well as Many other modifications. Of course the injectors were nowhere remotely close to “stock”, either at that power and rpm range.
While in the US Navy I was in Viet Nam on lcu boats. There was 6 engines on each boat, three 6-71’s for power; two 2-71’s for electric power and one 4-71 for the anchor winch. The engines just ran and ran. We had injector problems because of dirty fuel, so injectors was replaced frequently. The 6-71’s turned a 4 foot 4 blade prop, engine ran at 1600 rpm’s. A few times ( in time of need ) would be pushed to 1800 rpm’s. One day we blew an engine ( actually the twin disc clutch ), Pieces was every where.
Always liked the sound of the engines running at cruising speed ( 1600 rpm ). One class of boats had a pair of 6-71 together on one shaft, one right hand rotation and one left hand rotation, I think they was turbo charged units These boats had two shafts. Very dependable engines all the time, as long as the fuel was good and oil was maintained. Charlie J.
Thanks for serving Charles! Great story appreciated by this former Navy boat snipe. I sure do remember those twin discs.
I have 12, 8, 6 & 4 V-71 detroits firing both my fleet of tugboats and workboats as well as a few cranes and dredge pumps.
They are all Naturals and I simply love them. Not much is reliable in this world and at sea I have learned that I can count on only 2 things.
1.) Without fail the sea will be relentless and when it bears its teeth there is absolutely no room for error or hesitation, particularly in the engine room.
2.) My Detroits will never stop running and will dig deep to power through anything the sea throws my way. The only reason they will stop running is because I have safely returned to port and shut them down.
Great story. Thank you for sharing.
I have a 12v71tta, almost 18000 hours. Runs great. The 17v71n it replaced thru a rod out the side. I pulled all the pieces out, covered the hole with plywood, and ran 800 remember until late afternoon town arrived.
I’m 66 now and have been on fishing boats, in California, since 6 yrs old. 9 out of 10 trips the boats were powered by 71 series engines, the greatest majority were 6-71’s. 2-71’s were very common for gen sets. There was an occasional V8 Cummins and one or two D343 Cats. That’s it. Some of these boats were built in the early 50’s and still had engines with Gray Marine on valve covers. Also got to run some of the Long Beach to Catalina taxis which, at the time, were powered by 12 or 16V149’s. Deutz’s were used for awhile but most went back to the DD’s at re-power.
This was before the 80’s when Cal. and EPA got together for a massive re-power of commercial and charter fleets. So, started seeing modern 4 strokes creep in. Boat owners wanted quick turn around for an engine repair and Detroits gave them that. The sound of DD 71’s were a big part of my child hood.
Out of the million miles or so I drove 18 wheelers across the lower 48 many years ago, I must have around 400,000 miles in a Freightliner with a 8V71. They were commonly called 318s back then also. That was the horsepower rating with a specific injector size, mine had 290s. The transmission was a two stick 4×4, a Spicer, I think. It was the best designed of the two stick transmissions I had experience with.
All the Detroit two cycle diesels had what is called a ‘roots blower,’ a mechanically driven supercharger with two spiral, intermeshing, rotating lobed shafts that compress air. They were a basic part of the design and I doubt the motors would run without them.
Mack engines commonly had turbochargers back then. Later on turbos were paired with aftercoolers and the power really began climbing.
I own a 1959 GMC 860 short nose cab over hosting a 6-71 DD coupled to a 5&2. I love everything about my truck. He’s a grumbly looking ugly mutt that musters up one hell of a racket anything over idle. Yessir, my truck: all the right parts in all the right places. I love my truck oh yeah!
6-71 blowers only served to push air thru the two stroke intake ports.
Because the exhaust valves were still open when the piston covers the intake ports in the cylinder wall.
The blower was used to “scavenge” out the exhaust gases.
Not until a turbo was added did the over pressure help rise horsepower. The roots blower didn’t boost intake pressure over a naturally aspirated engine…
JohnW…… “The roots blower didn’t boost intake pressure over a naturally aspirated engine…”. Not sure where you got that idea from, however…. an NA (Naturally Aspirated) Detroit IS Roots equipped, and when the engine is “fresh” there IS about 3.4 to 4lbs of “boost” over atmospheric… depending on altitude, humidity, etc.
There is no such thing as a “naturally aspirated” 2 cycle GM Diesel (Detroit Diesel after mid 1965) without a Roots Blower, they cannot run without it… as the governor is also driven from the blower, as well as the fuel pump in many of the different models, though there were a Few which the pump was run off of the rear gear drive.
Yes i beg to disagree zs well back in the day there were after market gears that eould over speed the blower giving more boost i know i did it to an old 6_71 inline my friends and i hooked up to run a sawmill plus edger i set it at 2250 rpm then we changed the v belt pulleys on the mill to get the main saw to spin only.700 rpm the sae blades had to be hammered for that speed most old mills only ran 545rpm although i guess some of the electric mills ran 1000 rpm,anyway this thing really put out the power it was an old two valve head but i took out the little port industrial liners znd used a set of truck liners but stayed sith the little hv7 injectors this worked out great for a mill engine fuel usage was ok only aroung 35_40 gallons a day (8) hr shifth.Ps.the old fellow who sawed was the best i ever seen saw ,,the lumber stackers hated that engine and told me so!,one went as far as to tell me he hated me and that damned hot rod engine ,he said the old guy was killing him buring him in bourds ,those were the days RIP foxy
These engines seem to get everywhere. The first time I saw and heard one of these was in 1983 in the technical collage I was attending in England. A yellow 6V-71 with a Roots Blower sat on top. It was on a test bench and I could hardly hear the engine over the sound of the blower.
Jim, I beg to differ!
Any 2 cycle Detroit without a turbo was Naturally Aspirated. This is why it had a ‘blower’. They were blowers not super chargers. They performed the intake/exhaust function of the engine. A super charger is mechanically driven by the engine and force feeds air into the engine. A turbo does the same thing but is exhaust driven thereby making It more efficient. Note: I was on DDC’s mailing list X years ago. I received a publication near the end of the 2 cycle run wherein it was explained the blowers were going to be deleted from those engines. Reason – the blower was only needed for starting. They had found a way to start without it. The main reason was efficiency. Once the engine was running the turbo provided more than enough air. In fact the blower was impeding the performance of the turbo.
HOWEVER! The Series 50 & 60 were doing well and there was no point in going further with the 2 cycles. So the change was never implemented.
At the risk of being redundant: People have seen Roots type blowers on dragsters for years where in fact they perform a ‘supercharging’ function. On the DD’s they only provide that amount of air necessary for intake and exhaust. They are not boosting power.
Two cycle DD’s used a “Roots type positive displacement blower”. Meaning that per crankshaft revolution the blower was capable of producing an amount of air equal to the volumetric measure of the engine. The engines were exhaust scavenged. Just above BDC the piston uncovered a series of ports cast completely around the liner. The sides of the ports were angled. When uncovered pressurized air rushed into the cylinder. The angled sides of the ports induced a swirling of the air charge. This caused the air to sweep the cylinder – exhaust scavenging! The burned gases from the previous power stroke were then sitting on top of the swirling fresh air. The exhaust valves opened. The engines ONLY had exhaust valves be they 2 or 4 valve heads. The piston continues upward pushing the burned gases riding on top of the swirling fresh air out the open valves. The cam shafts are timed to close the valves at a point when the burned gases should be gone. The exhaust valves close and the piston continues up on what is now the compression stroke. Just prior to TDC the injector opens introducing a fine mist of fuel. When the fuel meets the ‘super heated’ air it ignites driving the piston down on the power stroke.
So to clarify the two strokes are: 1) Power 2) A combination exhaust/compression.
This also means that regardless of the number of cylinders, each one ‘fired’ on every crankshaft revolution. The four cycle engine can only fire half it’s cylinders per crankshaft revolution. This is why the Detroit’s were marketed as ‘Responsive’! I constantly see the old wives tales mentioned on these forums but never the other sales pitch: “Power on every down stroke”! Also, the two arrows : Good air chasing the bad.
The 2 cycles had an 80% compensation factor. Meaning they were comparable to 4 cycle engines with similar power ratings with 80% greater displacement, cubic inch. For example: When I was in buses we ran Detroit 426 CI 6-71N’s @ 218 HP alongside Cummins: 743 CI NH220, 855 CI NH250 and 855 CI NTC290. They all did the same jobs and often times ran together.
Another pet peeve: People think the 8V-92TA was the replacement for the 8V-71N & T – WRONG! Sitting side by side they are almost identical unless you know what to look for. The 6V-92TA replaced all versions of the 8V-71. The 8V-92TA replaced the 12V-71! I believe it was in an old Fleet Owner magazine. GM/Detroit took two matching Astro 95’s with trailers. They next matched loads to the pound. They ran a series of drag races. The 92 won! It out pulled the 12.
In buses I preferred Cummins. They climbed better. Spoke with the head of the shop and he said it was gearing not the engines. When I transitioned to trucks I regeared an international rearend from 4:10 to 4:44. I changed the direct 15 speed to an overdriven 15. I also changed injectors from the C60 (8 spray holes) to the N65 Brown Tag (9 spray holes). My mechanic estimated the 318 went to perhaps 335-340 HP. She climbed!!! A bunch of guys thought I had swapped in a Cummins because Detroits could not ‘hang on a grade’.
Note: The 60 injector series was Intended for Naturally Aspirated 8V-71N engines while the 65 injector series was intended for the turbocharged 8V-71T/TA/TTA.
Let me explain something that most dont understand about detroiters with the advanced timing the newer engines used (cam advanced one tooth) the.valves opened sooner letting out exhaust pressure sooner but the vslves also closed sooner trapping in more air so a little boost was present although not as much as a torbo model but none the less a little boost ,now on the older engines you would be correct and these older types are what the experts always refer to detroit did this timing change knowing full well they ran better!!!period hope this helps
CAN anyone tell me the mount differences . length, width, height ect of the 8v71 and the 8v92, thinking about a conversion in my bus.
RT, Today is Jan. 25th, 2025…. just happened by this site again and was reading more of the comments / replies, etc. I am not sure if your comment / reply, was intended for me, or not.. as there appears to be at least a couple of us in this thread, who’s name is “Jim”. I just finished reading your “knowledge” of Detroits… which for the most part is fairly accurate.
My own personal background with GMD/DD…. began with a 4 year degree in Engine Design & Theory, Specializing in Two Cycle, and was personally “tutored” as it were, by Mr. P. Nicholas… who was one of the lead designers of the very first two cycle GM Diesels, and the first running pre-production engines was a 4-71.
Long story short, after returning back from my last tour in “Nam”… and through him, I wound up in a proto-type advisory capacity under contract with DD, in developing a new scavenging system for the two cycles.
By 1971, I had also drafted a complete redesign of the “V” blocks and heads, which was promising… but, GM Corporate had final “say” in R&D expenditures for all their divisions, and with future, potential “issue’s” in the two cycles future they emphatically said “No”…. I later acquainted myself with EMD’s design for their engines, and discovered that what I “thought” I had “clean sheeted”… turned out to be significantly similar in overall design with theirs.
It all started in 1965/1966, when I designed my own new version of the scavenging system, utilizing a single axial flow turbo/supercharger that was mechanically driven via a thermatic / over-riding clutch system at cranking speeds and up to about (depending on engine load & exhaust flow/heat) 40+% of throttle, when the over-riding clutch would disengage and allow the turbo to spool up to rated speed.
Again… long story, further and greatly shortened… actual development of it by R&D, was “nixed” by the VP of R&D over at the EMDivision, when he caught wind of it, and brought to GM Corporate and DD’s attention that EMD not only had that very nearly identical design, but had a “grandfather” patent on it, that could not be copied in ANY way, shape or form.
So, though we did create a working proto-type with the system I had originally designed (in the mid 1960’s)… we could not patent or use it in production… but it did provide very interesting results and future possibilities for further exploration, but with the future emissions regulations already looming on the horizon, we knew that it would only be a matter of not that much more time, that our venerable two cycle would meet its demise…. the railroads (primarily) are still enjoying EMD’s 645e3 and 710 production (710) power, at least for export… we’ve lost great engine.
Had things been able to progress with my design… we would have an efficient (by design, the two cycle, already was) and very powerful two cycle, today for use in multiple roles of transportation and commerce.
There is much more that I could discuss, in terms of persistent (to this day!) MYTH’s with regards to… the two cycles “don’t make any torque, etc, etc… which all based on pure ignorance of the subject matter, but… it’s early in the morning, here…. and I have much to do, today.
As I stated above, I’m not sure as to which “Jim” you were responding to… but thought I would just jump in, and give you a brief, of my own personal background, from decades now part of history. Take care, and have a great weekend.
my dad has a tug boat with 2 1983 6L-7 1s and the port one blow up but still run hard to start will run (try that with a cummins) it blow up because the port water pump broke (i think it was made by cummins) i am only 14 and detroits may be befor my time but they are still the best
Designed to last and take a beating. A combination not often found today.
Timex will keep on ticking.
The Fire truck manufacturers really preferred the 53 series Detroit engines…….. it made for an interchangeable gas/diesel application as the 53 series is a near interchange for a gasoline engine and didn’t require gear ratio modifications.
Rupert Penjab…… Not sure where you got that from, however… more than 70% of all 2 cycle Detroit powered fire trucks were Series 71 powered…. there were a few of the smaller trucks that were 6V53 powered, but not many compared to all the 71 series over the decades.
As far as the “inter-change” part of your comment… yes, the 53 series could be had with either an SAE no.3 or no.2 bell housing which would make it pretty easy to convert from gas power to diesel… especially with a no.3 bell housing if in a smaller truck.
THIS!!! In over 30tears never encountered 53 series in a class 8 fire apparatus; 6-71 in Pumps and 8V71 or 6V92 in Ladders
Paul,
That’s a fact… but you left out the 12V71 that was used in a number of “hook & ladder” trucks, as well. There were a number of 6V53 engines used in numerous single axle fire trucks built in the late 1950’s (after 1957), and throughout the 70’s… in some parts of the country they were quite numerous, especially in rural depts.
Once in Beverly Hills, Ca I had an engine company pass me and he had a 12V71T. But it is called Beverly ‘HILLS’ for a reason. Some are short and steep.
Rupert Penjab:
I used to go to Valley Detroit Diesel a lot. Anytime I saw something interesting I had to check it out. I saw any number of engine companies. What most people call a pumper. They were all 8V-92TA’s rated from 445-500HP. This was in the mid to late 90’s. I also got to see a number of EMD’s. That was fun!
As for the 53 Series – grossly under powered. I have only seen US Forest Service fire trucks with the appropriate medium duty engine like the 3208. Remember prior to dieselization the 590 Hallscott was very popular in fire apparatus. The 53 Series would have been a step backwards. Further, power reduces the need for skill. Firefighters are not professional truck drivers. Yet they have to go anywhere. Prior to the proliferation of auto trans in their equipment I have never heard more than a 5 speed in their trucks. It requires a level of expertise to charge a really steep hill and nail the appropriate downshifts without stalling. However if you take a 2 axle truck weighing maybe 35K LBS and power it with a 500 HP engine capable of moving 150K LBS, there are no hills! Stick it in 2nd or 3rd and climb. No greater expertise required.
The 53’s were true heavy duty engines in the medium duty class. I could see them used by the Forest Service or ‘tiny town USA’. Small towns with small budgets.
observe high temperature on a 8v 71 detroit diesel radiator and fan cooling, ive flush radiator but temperature is still high
Hey Everyone!
I have a question about GM detroit diesel 3-71 marine engine. I am unsure of a couple of things about how to service this engine. I am looking for some helpful knowledge.
We have change the oil for the marine gear but don’t know where to fill up the oil fo the engine oil….? We have located an oil strainer but arent 100% sure if this is the fill in port? Any help would be much appriciated. There aren’t alot of helpful forums out there so im hoping someone in here can help me out!
Cheers!
I have two 6-71TIB’s in my boat and absolutely love them, the more I learn about them the more I love them. Really appreciate all the comments, love to the history. Thanks for your stories and service.
I have a 671 in my 1955 FLEX VL 100 tour bus. Jake breaks and Alison Transmission. What a blast to drive. I love the sound. I worry if I ever need a mechanic, I will never find one who can work on this old power house. Costa Mesa Cali.
Hopefully that day never comes. The 6-71 has been around for almost ever. Lets hope a few from the next generation learn a thing or two about them.
This is old but probably the best place to take a Detroit is Delaney and Alf, Bakersfield. I have not been there in years. If anyone has 2 cycle capability it’s them. They did a ‘full power’ tune on a 92 for me. Was told it should gain 45 HP. That and then some!
The bore and stroke on the 71 series is 4.5″ x 5″. They stopped making the 2 stroke Detroits in 1998 (they still make the 6V-53TI, 8V-71TA and 8V-92TA for military vehicles). It is interesting to note that the 2 strokers were cancelled because of being dirty burning and couldn’t be cleaned up to smog standards.
Yet the largest and most fuel efficient engine is a 2 stroke made by various companies. The largest has a 39″ bore x 135″ stroke (yes that’s 3″ over 11ft!). They power the big container ships and by cross section, look like big versions of Detroits.
Tom Christman…… Tom, just so you know, the 8V71T & TA is no longer available “new”….. the military orders dropped them.
There are Numerous large 2 cycle diesel engines and engine builders around the world…. not just “a 2 stroke made by various companies.” The Biggest that you were referring to is the Wartzila-Sulzer RT96A & C… originally designed by Sulzer before the merger with Wartzila from Poland. There are Many 2 cycle diesel builders in the world, including Fairbanks Morse from the US who have been around since quite a while before GM Diesel or EMD… originally since 1823…. before they (FM) started producing engines, actually.
671
Does anyone know where to fill the transmission fluid? Theres a canister above the tranny on the very back of the engine.
Thank you,
I need your help or that of any diesel mechanic you may happen to know.
The all-steel 1940 former Baltimore City Police Patrol Boat CHARLES D. GAITHER supports a Detroit 671 diesel engine in her spacious engine room. Can anyone date the engine by its serial number of 6718454. It has a five-pointed star following the number and we were wondering if this signifies it as being original, rebuilt or something entirely different. If it is the original engine, most likely it was manufactured between 1938 and early 1940 just prior to when the vessel was launched. Can anyone possibly give us more information about serial number 6718454 (star) Thanks.
Drew, I would be interested in hearing more about the history of this boat. If you can send in a photo or two along with any interesting details I’ll put together a post that hopefully will be seen by more eyeballs. Email eric@dailydieseldose.com
Drew Hall…. Hi Drew, you’ve probably long since gotten your answer… I just found this great blog.
What I can tell you is that for sure it would have been between 1939 & 1940, as the engines did Not go into production until 1939. I know this because I formally studied Engine design for four years back in the early/mid 1960’s and three of those years were under Pat N. who was one of the principle designers of the original Series 71, directly under “Boss” Kettering.
By the way… contrary to popular “myth”…. the Very First Series 71 built was NOT a 6-71… it was a 4-71 and I have an 8×10 of it taken just after its first start up, with Kettering, Pat and a 3rd R&D engineer whom I’ve forgotten the name of at the moment…. but I have the picture hanging righ over my desk here, which was given to me by Pat after I returned from VN in 1970.
Back to your question regarding the Serial Number…. I’m not sure where you got the number your showing but it sure doesn’t look like any Serial number I’ve ever seen for a 6-71…. it should start with (ie:) 06Axxxxxxx.
Also… I can tell you more about the engine from it’s model number, than its Serial number…. everything except the date. Can you give me the Model Number…. AND the Serial Number from the Machined pad…. located in my decription below?
OK…. a couple of questions for you, Where on the engine did you get this number? Off the “tag” on the rocker cover? The “star” you mention is Definitely NOT from the factory. There are TWO locations for the Serial AND Model numbers….. one of them is “incorruptable” (unless somebody bothered to grind it off – literally), and it is found on a machined “boss/pad” which, when FACING the Front of the engine – from the Front…. will be on your Left hand side of the block directly BELOW the top of the Block “deck” where the head and head gasket meet the Block…. and the machined “pad” with the Serial Number – followed by the Model number (below the serial number – on the pad) is just behind the very Front of the engine Block.
This machined “ID” pad was common to ALL Series 71 INLINE engines from One to Six cylinders.
The other location is the metal “tag” mounted on the rocker cover, of course.
Question…. is the rocker cover Stamped Steel with “knob” style hold-down bolts through the cover….. or, is it a Cast Cover with “DETROIT DIESEL” in Raised letters on the “angled” portion of the cover between the very top & sides of the cover?
Next question….. look on the sides of the block (either or both) towards the lower portion of the block….. does it have an “arrowed” circle with Detroit Diesel embossed & raised in the block – Or – does it have a raised or embossed “Rectangular box” with GM Diesel Power (with the GM in Large Caps at the top- Over the words Diesel Power in smaller letters and Diesel Power, one over the other) “in” the box?
The “heat exchanger” box at the top and front of the engine “could” say GM Diesel Power, Detroit Diesel or Gray Marine…. any of the three are “telling” for different reasons…. but, in trying to ID the engine…. the most important numbers and letters to me, are located at the location I pointed out to you… On the BLOCK….. NOT the rocker cover.
One more question….. do you know if has a 2 valve or a 4 valve head on it?
I cannot say for sure about the “star”…. but I’ve never seen one in relation to the Serial number…. but not to say they didn’t… but, again…. look at the numbers on the “pad” on the very Left Front of the engine block and IF you don’t see a “star” there, preceded by the serial number… then “someone” else stamped it – and probably during a rebuild (or a reman, possibly?).
Did you buy this historical old police boat? Good luck with it.
Hi Jim,
I am just finding this thread, and wondered if I can inquire your knowledge on these great engines. I have a few pictures of twin 6-71N and can email them to you. I am trying to figure out a few things prior to purchase. Please reply if you are able to take a look and exchange info…
Thanks,
Rex
rexw75 at gmail dot com
Hi Rex… My Sincere and humble apology to you, for Not responding. This “site” and this blog…. completely got away from me, and I have not returned to it, till just this morning.. Jan. 25th, 2025.
I assume that you acquired this boat, a long time ago (now)…. or, No??
I Will keep an eye on this site, to see if perhaps you do reply back… and I will respond, if you do. Take care, and have a great weekend.
i have a 83 white road boss with a running 671t in it right now with a hole in the block, no oil in motor or coolant, connecting rod smackin around and starts up in the pa. winters !!!!!! no bs. Awesome engine!!! try that with todays crap.
This is a very late comment but I hope you see it,,back around 1978 I was working for feeder off longing in pa,we had two old trees ts24 scrapers running around picking up topsoil,one day I’m going out the road following in a 637 cat when I look in the haul road I see oil lots of it,then I see a piston and part of a con.rod it was dinner time just then and this guy pulls up to be with the dozer.man and other pan drivers.just then I see our old.grumpy mechanic turn in in his service truck he walks over holding this grease rag in his han, cloud he says is you’re rear engine misfiring?old cloud says holding think so when the mechanic hands him the still very hot piston,I’m laughing my butt off then old mechanic says I don’t think ill ask you if you ever heard a loose valve setting,,,that was some funny.shit
The most reliable diesel ever built. The best sounding engine is the 6-71 and 8V71
natural in a truck fully loaded going up a grade. They go a lot better with a turbo and more economical but the sound changes. I want to buy an early 1980’s R600 Mack
bogie with a slightly extended chassis and stick a 318 or 6V92T in it and a 48 inch sleeper. Rt0 9513 Alcoa wheels on the front. I’m from Brisbane Australia.
Best diesel for sawmills an some trucks they will run for ever
I love old detroiters i have rebuilt a dozen or so over the years ,but i saw a mack 280 maxadyne engine installed on a sawmill nice and quiet essy on fuel the owner told me he only ran it at 1450 rpm but due to its trzctor typee govenor and macks abuillity to lug made the best damned engine he ever had!i could certainly.agree about the noise level! I ran several ts 24 terex pans over the.years with a v12 up front and 6_71 in the rear you were sure glad to get off at quitting time!
my field service book says Detroit made 568 inline 24 cylinder 71’sne seen one
I won’t think that there would be an inline 24 cyl. The V16-71 was two V8-71’s bolted end to end so I would the that the 24-71 would be two V12-71’s bolted end to end the same as the V16’s. I have never seen one though I have seen 16-71’s though.
Mr Barsby,
I used to get a Detroit Diesel magazine called Power Parade. I recall very well an article about a shallow draft Japanese patrol boat recently built to run down smugglers It had three engines: Port – 12V-92TI, Starboard 12V-92TI. The main center mounted engine was a 24V-92TI. Two 12’s bolted block to block.
So, if the 92 could be configured in that manner so could the 71. Detroit built engine families with a high degree of interchangeability & combine-ability.
There would be a cylinder firing every 15 degrees… That would be SMOOTH.
way back when there was a setup with (4) 6-71 attached to a it as an inline unit sometimes called a quad unit, this was possible because the ends of the block are the same, this way the block and head can be flipped around. this one idea allows the 71 series to be assembled 8 different setups 4 of rh rotation and 4 left hand rotation
Years ago I had a 125kw gen set powered by a V671 . It ran at a constant 1800 rpm. I never leaked a drop of oil and was the only diesel that I have ever seen that the oil was the same colour going in as when it was changed. That oil never got black. They ate great engines.
Barsby,
FYI: Detroit Diesel began as General Motors Diesel. GM manufactured gas engines with ‘V’ blocks -V6,V8, V12 & V16. When they decided to manufacture ‘V’ blocked diesels they reversed the designation to avoid confusion: 6V-71N, 8V-71TA, 8V-92TTA, and so on.
Any idea what a 6-71-based design could be pushed to, hp wise, with modern metals, rings, bearings, etc and not worrying about emissions?
Kevin Dutchers,
Sorry… just found your question. The 6-71 “Can be built” to over 500 hp staying Under 2,55o rpms. They built a 6-71X in the “back room” at DD back in 1969, and had it at a steady 750hp for Two Months on one of their dynos!! If I were you, I would find a 6-110 (660ci -vs- 426ci) and “build” that.
J&T Marine were famous for their 450+ hp 6-71Ti’s….. they’re still in business and still build/rebuild the 2 cycle “Jimmies”… look them up, they may even have or know where you could find a 6-110, although Williams Detroit Diesel up in Vancouver, BC Canada bought all the “rights” from DD to the 6-110, and still have engines and parts.
RT…. So sorry, but I must disagree with you, my friend… with regards to your statement regarding a “24V92Ti”.
No such assembly was Ever produced by DD. In fact, the series 71, was the Only “family” with a “V24″…. the reason being is that they would have had FOUR (4) Series 92 engines in a setup like that, and far too much redundancy and potential issue’s.
The HP produced by a hypothetical V24 in that family, would have been easily matched, and with more torque by the use of the Series 149 – V12T/Ti…. which is what DD Marine, did.
Having said all that… it’s Not to say that “someone” (company or otherwise), may have cobbled together such a setup…. but it’s Highly unlikely, considering all the internal and external complexities of building such an engine setup, especially from the Series 92 family.
Also, and just so you know… the Series 71 “V24” was NOT assembled by DD, either…. all their “Special Build” orders were handled by Stewart & Stevenson…. the largest (2 cycle) DD dealer and re-manufacturer thereof, in the world.
I once met a.guy (Richard M benign who workforce Detroit for 16 years as a research designer he had some really crazy stories about Detroit drama told me he helped build a pair of 6_71 Detroit ers used in the boat called BANKSHOT used in the movie Bermuda triangle,he said they.put two big oxy bottles on both sides of these engines with one minute timers on them after building so many rpm the bottles would inject oxygen strait into the blowers just underneath where they noted down ,they also installed the oil rings upside down so as to carry.oil up the liner f I remember right they both put out over 900 up !
My company dismantles and parts out old Euclid and Terex off road haul trucks. We still get to play with these engines almost everyday. Such a great sound!!
Some guys have all the luck!
I miss the old 2 cycle Detroits, very reliable and parts were inexpensive compared to Cat or Cummins. The ’71 series were great, the ’53 series were junk, also the ‘149 series were excellent as well. Shame they are no longer in production.
Ever look at emd locomotive engines up to 20 v 710 cubic inch per cylinder 950 rpm5000 hp used on emds sd80 sereies locomotives (no longer in prodution) but huge locos ive seen two about ten years ago as this is written is was on csx line,, i guess csx traded them to anouther rr after acquiring them with the conral take over if memory servers me correctly only around 20 were ever made ,but i understand emd still makes the v20 710 series for generator plants and ship power!
Im looking at a boat with GM 4-71-TI’s with 6000 hours. What What I’ve read is they last a Long time but are they at a point of needing replacement or overhaul. Thanks for any help
Just stripped for planned maintenance, a 6-71 ti marine gen-set after 15000hrs work @ 1500rpm (50hz) mostly under heavy load and still has honing marks inside the cylinders!
Regular oil changes, run warm but not hot and it’ll just keep going.
great stories. I might be able to keep this going. I have a 6-71N in my 44′ commercial vessel, keel cooled. Model:6-71RC7 Serial:6713433 still has original stamp plate. local diesel shops tell me she’s an oldie. Runs like a top, sounds like a jet engine at the exhaust. I am having problems finding a specific manual for this ol’ girl. engine temp got to 190 and overflowed coolant out of the expansion tank. I changed out the coolant, flushed the system as best I could and replaced with fresh coolant. Ran it for approx. 15hrs and she got up to 190 again for about 10 min and back to normal operating temp at 180. Next stop is thermostat but it worries me that the system pushed back pressure through the expansion tank. Any thoughts?
At mass maritime they still teach the cadets on in 6-71 s, which is great, my boy just went through the class and will rebuild the 4-71 that sits right behind me in the crane I run every day. The work boat has a 6 -71, and the tugs have 12-71, all naturals getting 25000 hours on the tugs mains before overhaul. They may require some skill to get them to run perfect but this old fool can always make em run, good enough.
Had to get teir 2 motors in a new machine, lots and lots of wires, no tinkering those babies home when they stop that’s that. When you out on the water……..
Greetings,
I have been considering buying a cabin cruser about 35 to 38 feet long but most are gas powered and they really suck it. I would like to talk with anyone who has converted a boat to diesel. I like the thought of the 4 cyl. 71 series Detroit. but have no experience with it other than reading about it any comment?
Look at a 3-53 or 4-53 they are a lot shorter than the 71s and much lighter.
Belive it or not detroiters are very heavy for thier cubic inch. More than cummins or cat look it up i was surprised too!
Hi all. I’m looking for a bit of help finding some parts for a 3-71. My plan is to install it in a 1966 Dodge one ton so I’m looking for an automotive governor and a 6V-71 truck exhaust manifold and the bit to hook up the pipe to it.
Around Seattle you use to be able to find Jimmy parts just about anywhere now it’s good luck!
Kriss,
I assume you have solved your problem by now. The 71’s are to big and heavy for a 1 ton truck. The 4-53N & 4-53T are ideal in that application. They weigh around 1300 LBS. which is almost twice the weight of a big block gasser. They are heavy but they are true heavy duty engines. They use replaceable liners – cylinders walls.
A mechanic at my old shop took an old army pickup with an inline 6 gasser and swapped a 350 Chevy. He said it ran better but not what he wanted. So he put a 4-53N in it. It ran better. Next he turbo’ed it and got a 4” muffler off an old Pete. He told me he had no problem pulling his boat or travel trailer over the same grades his gassers struggled on. That thing sounded great. If you put a 71 in it would be too much weight on the front axle. Unless you counterweight the bed you could have control problems. I would also expect front end component failures. The 4-53 was a popular swap. You can find it all over the internet. The easiest swap for you is a Cummins B Series .
I know of one pickup truck an old dodge 3/4 ton that had a 4_53 installed it was up against the governor at 50 mph!in high gear i dont know the rear end ratio but the guy came into my freinds shop looking for a faster set of gears for it!
What is the weight of a 6V-71 engine.
Can’t find it online somewhere….
No cooling, start motor or generators installed.
I need to put it on a trailer for transportation.
Fred
Fred… I’m sure you have your answer by now, but in any case… the 6V71 less parasitic accessories is in the neighborhood of 2,100 lbs.
Have fun and best of luck with your project.
Around 2250 pounds
I have a customer that ran twin marine 12v71’s out of fuel. I installed new seperator filters, secondary filters, fuel lines, bled the system and both engines fired up immediately. Both run great but after they reach operating temp, 1 stalls out. It will start again only to run a little while then stall again. What is the issue?
1. Bad fuel pump.
2. Dirty injectors.
3. Fuel regulator.
4. Air intake.
5. Governor adjustment.
Thank you.
A plugged vent in the fuel tank.
I was in a vo-tech high school back in the 70s and we had a couple of Detroits in the shop. We had a 8-V71 out of a Bus and a 2-71 that they said was off a military generator unit. They were both a joy to work on and to this day I love the sound of a Detroit.
My buddy, from high school, became a curator for a railroad museum. I was visiting one day and we cranked the big Detroit in an over-the-road, Santa FE war bonnet, a-unit. What a thrill! The valve cover was off and you could watch the rockers slowly moving up and down as the engine spun over. A release of the compression release lever and it came to life.
James… “and we cranked the big Detroit……”. The EMD locomotives, although a division of GM (now Caterpillar), and the EMD prime movers (formerly Cleveland) used to run the generators… have Absolutely Nothing to do with Detroit Diesels whatsoever…. just so you know.
Yes, they are both 2 cycle design, and they both utilize Unit style injectors, and valve “bridges” for actuation… but the similarity ends there.
Talking about stalling problems , two marine 12V71 naturals housed in a Mark ‘ll patrol craft fast Swift Boat.
Both . The port engine stalls eff hen tsken out of gear and put bavk into gear ig stslls why?
The problem is most likely high fuel pressure due to a plugged restricted fitting or closed valve in the return fuel line or a stuck relief valve in the fuel pump.
Hi guys
Is the engine block the same size in a v671 and a v692 ?
Thanks
The racks can get bound up and will be unable to keep the engine from stalling at idle due to high fuel pressure. A sticking fuel pump relief valve or a return line restriction i.e., plugged restricted fitting or a valve shut off.
No, The 6V-71 and the 6V-92 blocks are completely different. The 71 has dry liners and the 92 wet liners.
But they are the same size. 8V’s also. You can swap out a 92 for a 71 with no changes in the bodywork … at least on a bus. Been there, doen that.
The older 71’s were air cooled. I had a 1965. The air box covers were big ovals. The later model water cooled liners had smaller rectangular covers over the air boxes.
During Viet Nam, I worked at a mini shipyard in Quih Nhon. One of the boats we worked on had Detroits. The mechs overhauled 12V71 engines, one pair bolted together for each prop, about 4 FT dia. They had twin superchargers and turbochargers. I am not a diesel mech, but when they were done overhaul, they ran around 3900RPM, I think, during sea trials. They were great to hear run!!!
I have 671 TIB in my boat with 3000 hours on them. I changed the fuel filters every 50 hours and the oil every 100 hours. I have had the boat 14 years and only replaced a starter in 14 years. The motors do leak some oil after 60 hours but not much. I run the engines at 19 -1950 rpm.(not 2150).
How many hours will I get out of these motors??????????????
TY
Dan Mag
Dan Mag…. How “long” will You… live? If properly maintained as you indicate (and hopefully you are using a LOW Ash – straight 40 wgt oil – ONLY!), these engines are generally good for 10,000+ hours…. I have heard of some going 15,000+!!…. and at the rate your going, with “only” 3,000 hrs in 14 years… they may outlast… You!! lol ; )
I worked at Redford for 22 years, leaving in 1988 when sold to Penske. As a Receiving Inspector there quality was important. Every outside purchased part not made in-house had many checks to go through before acceptance. I believe we made the highest quality engines and history and customer satisfaction proves it. The 2-stroke 53’s and 71’s have been proven in war and troops swear by them.
hi eric, what´s up?
my question is:
i have a 671 engine in line model 1063-7005 (typical power generator unit) and this engine was tested at 134 hp at 1200 RPM ,so i´d like to turn this engine in 1063-7000 (typical industrial power take off unit )with 180 hp at 1800 rpm.
Is it possible?
Regards,
Ednaldo
Ednaldo,
I just happen to find your post here… and I’m sure that you’ve long since found your answer by now…. but, just in case and for someone else who might be wondering about the same question, or just wondering about what the “possibilities” are with these engines, the “short” answer is…. “the sky is the limit”….. and stopping just short of “insane”.
What exactly are you powering with this 6-71 you have? How much power would you like to have from this engine? You can go to about 450hp (with a turbocharger & 4 valve head) and still have Lots of good, dependable reliability and longevity.
I will tell you that back in 1969 they (DD engineers) built a 6-71″X” (for experimental)… and that they ran it steady on one of their in-house dynamometers for two weeks straight, under full load at 2,700 rpm… yielding 750hp and nearly 1,430 ftlbs of torque.
There are literally dozens of different injectors – but, you have to know the different types and how they affect the power band of the engine. Also, you can “safely” govern them up to 2,350 rpms (no load) with the valve springs you have (unless of course, the engine has LOTS of time on it and the springs are getting weak), but if you want to go higher, then you must change out the valve springs for the marine units… of which there are several different spring rates.
Also, you have a 2 valve head on your engine (if, it’s all “original”), which is fine for the Low hp, low rpm “breathing” it seems you want to stay at…. but IF, you want to go up higher (over 200 hp & higher rpm range), I would definitely replace it with the 4 valve head.
We had a 12-71 in the Lady Butterfly – Pro Semi Sled Pulls (NTPA, ECPA, etc) for Years…. and were turning it at 4,000+ under load and Never blew it up… though it did spin a main bearing once, back in 2006. The power was right around 2,500 hp and 3,000 ftlbs of torque…. but lots of “tricks” to get it there, including “hand built” 240mm injectors (“fuel faucets”)…. I don’t “share” any more than that… sorry. lol : )
I’m working on a 1974 tug boat powered by two 12v71s with blowers. Throttle hung wide open causing it to run about 2700 rpm. Spitting out a few valve springs in the process. New engine has been sitting on an engine stand for 12 years and hadn’t even had oil run through it yet. It shuts off when taken out of gear and doesn’t hesitate to restart. What adjustments can I make to stop that from happening?
I have one doing the exact same thing. What did you find ?
Guys, I have a 1984 Post Marine 43 with 2 1988 Detroit 671T and they have Jabsco saltwater pumps on them. But been having trouble with them blowing water like crazy. Had the port rebuilt but still throwing water but not as bad as before, but bad enough to give me some concern. Can anyone tell me if there is different maker of pumps that will work for me and not cost me a arm and a leg.
Robert Wright, I am wondering if you still have your Post 43 with the DD 6-71s and are still having this issue. I know of a similar boat and would like to exchange engine info if you are available? Thanks, Capt. Rex. I live in Florida and email is: rexw75 at gmaildotcom
thanks,
Rex
Sorry about not getting back to you earlier but yes I still have the boat. Had to get the raw water pump rebuilt and that fixed the problem. Due to health issues I haven’t been able to run the boat for about a year. Doing a little repair right before I get her sold. Thanks for replying to my comment. Be safe. Fair winds and calm seas
Are there any exterior differences between the 2-valve and 4-valve heads? My marine 6-71N’s are difficult to work around.
Thanks
Mike Partain…. Sorry for my Late reply to you.. just found this post. I’m sure you have your answer since quite a while ago, and the answer is No, the differences are only Internal, with being 4 valves and the “bridge” to actuate two valves per arm, rather than just one…. everything else is identical.
Are you thinking of changing from one head to another?… and IF so, I would think you’d be going from 2V to 4V and not “backwards”. In what way are your 6-71’s “difficult to work around”?? In terms of space?…. and what does that have to do in relation to a 2V head versus a 4V head?
I have 2 v71 12 cyl in a boat hadn’t been running for many years one is fine but the other went up to 3500 rpm kept running when I pushed the stop.
One service guy told me to dismount all injectors one or several is stuck in full throttle ?
Any advise please
Per
Italy
Per Landin,
Well… that scenario is entirely possible, However… “usually” the only time you will run into that situation is after the engine has been “sitting” for a while…. like a year or more, and that is Thee Number One thing to ALWAYS check for when starting a 2 cycle (mechanical) Detroit for the first time after it has been “sitting” dormant for any good length of time… ALWAYS check for a stuck injector(s).
IF you find one, or more…. bar the engine over (by hand) at least TWO full revolutions and then recheck them… if still stuck, flip the rocker arm (or, arm and Bridge if a 4 valve head) and try Manually depressing the plunger spring on the top of the injector, IF… you cannot depress the plunger of the stuck injector(s), then you can try removing the fuel “jumper” tubes and spraying some lubricant into the fuel Inlet and let it soak in for a few minutes and then try depressing the plunger again.
Of course, before all that… you can clamp onto the fuel rack tube with “vise-grips” and spray some “anti-rust” lubricant onto the injector control arm and its “teeth” and try manually working the injectors until they are all working freely… disconnect the linkage from the governor, first… then remember to replace it when finished.
First, I’m looking for information on Series 71 serial number vs year of production prior to 1960. I have references identifying SN to year of production after 1960 to end of production, but not before. Was the same system of numbering always used since 1938? I have two 2-71’s 2A14395 and 2A8195.
Second I’m trying to find out what year they changed from the low to high block design. Older service manuals show it effective 3A-8330, 4A-19529, 6A-16283, 8A-133, 12A-1345, 24A-140 (the 8A, 12A, and 24A engines being twins and quads). The 2-71 was never changed to the high block design. Considering the number of engines reported built in WWII, it would appear this was a running change during the war which seems unlikely. Also a Gray Marine Manual I have, copyright 1944 only shows low block information. Were there reliability problems with the 2 pc head gasket of the low block or was it changed due to higher cylinder pressure with turbocharging in later years?
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I am overhauling my US Navy surplus LCPL 36 ft, built by Polaris Marine in 1981, in Everett Washington. Does anyone know where I can get a tech manual for the boat? 8-71 TI Detroit Diesel.
Try Abebooks on line (www.abebooks.com) they handle used and vintage books. I just looked up “Detroit Diesel 6-71” and found several. They are pricey though
I have 6-71 na in a 1950 Moreton bay cruiser built in Queensland Australia in 1950. I always avoided the mention of a two stroke diesel let alone owning one until I had this pleasure of working on the 6-71,it appears to be a landing craft gray marine,I even found the old battle governor in a box of bits,if anyone wants it for a restore I will send it.the engine is such a pleasure to work on ,simple,rugged and now I can’t wait for any excuse to run it up,the boat before this one was a ww2 hdml79 running two 1879 Which we lost, getting our hands on another ww2 relic is such a privalige,
Reading the previous comments makes me proud of all who had much to do with these wonderfull engines,I only hope future generations will appreciate the screaming jimmy ,
I’m used to 4 strokes and it takes courage just to hold the throttle at 1900 but I’m getting better at it .pretty soon I reckon running at those revs will have a carming effect
Three cheers for the 71 series May you Reign forever,
Hmm looking at a 12v71 old but runs attatch to compressor. Was thinking of bolting to a. Generator to provide power to a off grid subdivision full of powerless cabins . figure the total need would be for 200 cabins. any ideas as to what might bolt up to the 12v71 thanks pat
I could send you details of what we have bolted to ours? I’ll see if I can find a data plate. It is a 200KW unit delivering 415VAC 3 phase at 50hz.
Hi hoping one of you may be able to help? We have a 12V71 on an offshore gas platform in the North Sea of the UK. It’s being used as a generator and is still in use after having been originally installed out here by Phillips petroleum back in 1968. We are about to install a new digital engine controller to it but need to know how many teeth are on the flywheel. This is for a magnetic pick up for the speed controller.
Any of you guys happen to know what that figure may be?
My dad had a old 63 foot SAR boat with 6/71 gray marine he liked them better than his Gardener,s. I love how easy it was to maintain them.A GM guy down on the Tweed in NSW has some 110,s.
Great blog! Just stumbled on it, what a wealth of information on a great series of engines. It leads me to ask some questions on a relatively rare (I’m told) 6-71 configuration that I maintain on the schooner ADVENTURE out of Gloucester, MA. The engine is a right hand rotation, 4 valve per cylinder, slant configuration that I’ve never seen before. Unfortunately someone ground off the serial and model numbers so obtaining spare parts is a bit of a challenge. The set-up makes the engine a dream to work on though with the blower and starter on and near the top of the engine and the valve cover at an angle and low enough so that access to the valves and injectors is very easy. I do know that the engine was rebuilt at NNSY sometime in the 70’s and was bought from Navy salvage, unused, in the early 2000’s. I’ve looked in all the sites that I can find trying to locate an engine / parts manual to no avail. Does anyone know a source of data for this configuration, and/or a way that I can back into serial number for this particular engine? I can work out the model number based on the information provided in the typical in-line upright configuration manual.
This baby runs like a champ! I want to keep her that way.
Bill Whitney
Chief Engineer
Schooner ADVENTURE
Gloucester
I remember these this engine was in the 33 ft boats it was known as a 6088 or a 6087 the ones we had n60 injectors and the long port liners it also had a 4valve head and the limting speed gov.
It is a great blog, I hope you can help me my father owns a truck with a 6-71 Detroit engine with a 9-speed gearbox but we want to change it, which gearbox do you recommend?
15 speed! It will give you the best of all things. Normally you run low and high range, 10 gears. Only when you need to get a heavy load started or a steep incline would you engage ‘deep reduction’. You do not have to go to deep 5th before shifting into low range. It depends upon the situation. There is a one gear offset between deep reduction and low range except for first. Deep first is 2 gears below low first. Deep second is below low first. Deep third below low second. Deep fourth below low third and deep fifth below low fourth.
If you want to come out of deep first or deep second the upshift is to low range first. let’s say you are in deep reduction 4th. The upshift is to low range 3rd!
Now! YOU MAY NEVER PRESELECT THE DEEP REDUCTION SHIFT!!!!!! Meaning you cannot flip the deep switch while in gear then move the selector when you feel like it or lift off throttle and have it drop in. The moment you flip the switch in or out of deep – it goes! You must have the selector in neutral with the clutch in any time you flip the the switch in/out of deep.
You have a choice between a direct 1:1 ration final drive or overdrive 1:.76 ratio. What that means: A direct 1:1 ratio happens when the transmission output shaft turns at the same rate, RPM, as the input shaft. In overdrive, let’s say .76 the input shaft turns .76 of a revolution per complete revolution of the output shaft. Simply put, in the above example when the transmission input shaft driven by the flywheel rotates from 12 o’clock to 9 o’clock the transmission output shaft makes a complete revolution 12 o’clock to 12 o’clock.
You have to decide whether direct final drive or an OD final drive suits your application best. Also you can change rearend ratios to better work with a given transmission. If you do not know the rearend ration drop the driveshaft at the rearend so that the U-joint stays with the driveshaft. Look at the flat end of the shaft in the center of the rearend yoke. You will see two numbers stamped into it. Divide the large number by the smaller. That will be the ratio 3.70, 3.90, 4.11, 4.33 etc.There are a lot of them. Enjoy!
My first experience with a Detroit Diesel was while I was working for Shell Canada in southern Alberta. We were doing a workover. The service rig had a twin turbo 12V71. We had a rental triplex pumps with 471’s. One 471 wouldn’t start. I called Waterous in Lethbridge to come and fix the engine. Awhile later, a Guy showed up in a pickup truck. I thought he was lost and went over to talk to him. He said he was here to get our Detroit running. I was expecting a big truck with a crane, compressor, etc. I asked where his tools were. He said right here. He had a screw driver, a crescent wrench, and a pair of pliers. He said “if I can’t get her – it’s a major”. Ten minutes later he had it going. It was amazing!
Hello All, I have a ’74 Matthews with twin 8V71 TI’s. This boat has not been out in over ten years and one of the pair is stuck and won’t turn over on the starter (which has been rebuilt). The engine has run in the past and while smoking some at start up, cleaned up after about ten minutes and ran well; both ran well and have about 1800 Hrs. My thought is to try a circulate oil through the system with some kind of external pump but don’t know where to start, and would really appreciate some advice. Also, is it possible to soak the pistons with some diesel before turning over? And also a thought of making a long, kind a breaker bar to attach to the front pulley(?) to break it loose ( although that bar might have to be twenty feet long!?) And if this is not the right forum to post on please point me in the right direction, but you all seem the most open to questions. Thanks for your good advice, Murph
I have a 8v71 Detroit mariner gearbox and it doesn’t engages it take some time to engages i have fitted new oil pumps the back one and front one(hydrolic)
But is still very slow to engages I’m on
The Nile river and not much is available
In South Suddan eney advise
I hooked my battery but nothing is coming on I’m working on a 01disel but with 4 battery’s help Detroit engine 60 series
hi jim here i have owend a 471 detroit for some years rockford clutch behind it my question is this serial no on right side top of the biock is 7 digit number rd below i found 72 vintage engines and up i think i could own a very early detroit 1938 to 1945 thanks jim
I know of one pickup truck an old dodge 3/4 ton that had a 4_53 installed it was up against the governor at 50 mph!in high gear i dont know the rear end ratio but the guy came into my freinds shop looking for a faster set of gears for it!
One thing about old Detroit error just when you think you’ve seen them all,a new setup appears that you’ve never heard of,last week I saw an old 8v92 with electronic injectors,,,this is news to me but I saw it!
CAN anyone tell me the mount differences . length, width, height ect of the 8v71 and the 8v92, thinking about a conversion in my bus.
can anyone help with the id of this ENGINE, SPECS, TIMING, INJECTORS ECT. 8VA-431743 / 7087-7940 THANKS
What is a low or tall block design 6-71?