GM 71 Diesels

[padgett]

Note: this came out of the discussion in the GMC V12 thread but just too different & did not want to hijack.

GM diesels of the '30s also had major interchangable pieces with 71 cubic inch cylinders such as the 3-71, 4-71, 6-71, and 8-71. All were 2 stroke supercharged diesels. 6-71 superchargers are still popular on top of hemis.

Later there were also a 51 (later 53) and 110 versions. Diesels and particularly 2-strokes, respond very well to boost.

The 71 series ranged from 213 cid to 568 cid and from the late '30s into the 90s were used in just about everything.

In the fifties GM had three diesel divisions: Detroit Diesel (automotive), Cleveland Diesel (mostly ship engines), and Electro-Motive (railway engines) though there was some cross polination.

Since the '30s GM was in the lead for diesels in the US. Too bad the automotive market was destroyed here in the 1980s (please see Hanlon's Razor - might make a bad movie on the SiFi channel)

It is interesting to conjecture what might have happened if 50 mpg diesels had become common in automobiles in the US as are everywhere else.

Just a note: Diesel fuel has much better lubricating qualities than gasoline and diesel engines/injector pumps are designed to take advantage of this. Blending ethanol with diesel markedly reduces these qualities and may become corrosive. It also lowers the Cetane number and increases flammability. You can also get more diesel from inferior petrolium (e.g. Alaska) than gasoline.

For more than you ever wanted to know, see here.

[rocketraider]

In the fifties GM had three diesel divisions: Detroit Diesel (automotive), Cleveland Diesel (mostly ship engines), and Electro-Motive (railway engines) though there was some cross polination.

Since the '30s GM was in the lead for diesels in the US.

With the in-house Diesel experience they had, I don't understand why they would not allow Oldsmobile to take advantage of ANY of it when they decreed that GM would have a Diesel passenger car/ light truck engine and that Oldsmobile engineering would design and build it.

I'm going to refrain from any GM-bashing here as my low opinion of their latter-day management is no secret, but sometimes I think they had their heads so far up their butts they could see what they were going to have for lunch the next day.

[padgett]

The sad thing is that we are all paying for that one blunder the general made a generation ago.

Then again, if we had 50 mpg family cars with 500 mile ranges, would we have ever gotten the Prius ?

[NTX5467]

From the earlier days of General Motors, there have been MANY things and areas in which they had complete market superiority for many years. The 2-stroke diesels were unique, when all others were normal 4-stroke engines. Certainly "Unique in all the world" (my apoligies to our '61+ Thunderbird enthusiasts, of which I'm one).

From what I understand, Olds got the "diesel deal" for one, possibly two, reasons. One was that of all of the GM V-8s, the Oldsmobile "bottom end" was the strongest. The other one might be that there were still some remnants of Olds being the "advanced engineering" division of GM still around?

I remember reading in a "Motor Trend" article on the then-new Olds 5.7L diesel V-8 that although there had been many diesels designed previously, not much was written down about combustion chamber design and such, so it was "cut and try" for the Olds engineers. But I also suspect that they had to acquire and dismantle the Mercedes and other European diesels to see waht made them tick.

One "tick" that should NOT have happened, by observation, was their use of an "agricultural-grade" injection pump, which usually ran for hours on end at constant rpm! RoosaMaster built a good pump for what it was being used for, but there HAD to be a reason another choice was not made in this area! Plus, I understand that some operative in GM had some influence in the fuel tank sending unit's fuel intake design, which later turned out to be a reliability issue for the pumps. It might have been that RossaMaster was the only USA-brand pump available, that was any good? Yet Chevy LUV diesels (Isuzu 4 cyls) had an electronic DieselKiki brand pump on them that worked great.

Obviously, there were some quality control issues, but the American public was not ready for diesels back then, either, by observation. Some people bought them that had very little "business" with them--period.

In more current times, diesel designs have improved phenominally between "then" and "now". Plus many are more attuned to diesel ownership and "quirks" thereof, like the correct motor oil. Modern diesel cars seem to be everywhere EXCEPT the USA, but as VW has re-openned the diesel car market, that seems to be changing.

With the earlier Olds diesels, with the added fuel economy using higher-priced diesel (compared to 87 pump octane unleaded fuel), plus considering the 6 qt oil change, I figured it was a 100,000 break even point for an Olds Delta 88 diesel compared to the similar gas-powered car. The additional CAFE fuel economy of the GM diesels helped get GM through a fuel economy transitionary period, basically. It kept the fuel-thirsty 454 C-30s on the road for a few more years until updated designs could be put into production. This kept GM competitive in their light duty trucks, which was very important, especially with the Ford/IH diesel being around.

Still, I concur that GM should have been able to "do better", all things considered.

Just some thoughts,

NTX5467

[Dave@Moon]

I'm going to refrain from any GM-bashing here as my low opinion of their latter-day management is no secret, but sometimes I think they had their heads so far up their butts they could see what they were going to have for lunch the next day.

...But that's not bashing, right Glenn! :rolleyes:

[Dandy Dave]

Allis Chalmers used the Detroit line of engines in it's construction equipment in the 1940's and 1950's.

VanNatta Allis Chalmers HD-21A Bulldozer

Here's an HD 7 pushing snow with that Detroit sound.

HD-9 Pushing snow.

HD-11 with a 6V-71.

Edited December 8, 2011 by Dandy Dave (see edit history)

[Restorer32]

I spent the Summer of 1969 doing archaeology in Israel and was amazed that nearly ALL the taxis were Mercedes diesels. Did anyone ever have an Olds diesel that was actually reliable and long lived?

[rhb1999]

In the fifties GM had three diesel divisions: Detroit Diesel (automotive), Cleveland Diesel (mostly ship engines), and Electro-Motive (railway engines) though there was some cross polination.

In all the years building and repairing yachts, I never heard of a Cleveland Diesel, it's possible they were only used in large ships. The only General Motors diesel I saw used was the Detroit Diesel, and these were boats from the '50's and '60's.

[Guest Al Brass]

I believe Detroit Diesels were actually a Winton design and were bought by GM when they expanded into rail, General Electric was purchased in the same expansion.

Fuel consumption and emmissions were the reason they died out but they were a good engine in their time and there would be thousands still doing a good days work.

Al

__________________

[padgett]

Interesting a brief history of Cleveland Diesel which did start out as part of Winton. Became the Cleveland Diesel Engine Div. of General Motors Corp. in 1938 (another source says GM bought Winton Engine is 1930). Produced primarily submarine engines during WWII.

GM Diesel Division was formed from CD but CD was closed in 1962. In 1965 GM Diesel became Detriot Diesel which became Detroit Diesel Allison in 1970.

The family tree is more of a bramble bush but CD was more large including over 1000 cubic inch V12 and V16s and became Electro-Motive Division which became EMD and produced railway engines while DD focused on smaller truck and bus engines.

Does that help ? (btw this came from a few minutes sometimes contradictory surfing).

[rhb1999]

I believe Detroit Diesels were actually a Winton design and were bought by GM when they expanded into rail, General Electric was purchased in the same expansion.

Fuel consumption and emmissions were the reason they died out but they were a good engine in their time and there would be thousands still doing a good days work.

Al

__________________

I agree. I understand reasonably priced both new and to rebuild too.

[R W Burgess]

I agree. I understand reasonably priced both new and to rebuild too.

I agree although they did have other issues, like oil consumption and slobber. The later 92 series engines reduced the slobber issue, unless they threw a rod, of course.

Ask me how I know!

The two cycle engines seemed to work much better under constant power as used in marine engines. With marine engines they could put out much more power too, since the heating problems were cured by the constant temperature of the cooling water.

Our company had up to 5 Detroit powered heavy trucks back in the early 80's. We then went through a Cummins phrase, and are now dealing with Catapillars, although the EPA is doing its best to outlaw them with regulations, in this country at least. Interestingly, engine life has really improved in the last 30 years with all engines, in our case at any rate.

Wayne

[Guest Gary Hearn]

I have a Detroit 4-71 (4 valve) that was used to power my sawmill. It has around 8800 hours on it and as far as I know will still power up and run. I sold the mill, planer, live log deck and power unit, but the purchaser has never picked up the latter two items. It all came from up the road from Wayne in Sparta, VA.

My father in law used to have a 65' Hatteras boat that had twin 8-92's in it. At cruising speed it would burn through about 75 gallons per hour.

[Dandy Dave]

I agree although they did have other issues, like oil consumption and slobber. The later 92 series engines reduced the slobber issue, unless they threw a rod, of course.

Ask me how I know!

Wayne

Ohhhh Yeahhhhh! The I R air compressors would use, or leak, a gallon of oil in 24 hours if the Detroits were in good condition. More, as in up to 3 gallons, if they were ready for a rebuild. As a maintanance mechanic at Catamount Ski Area in the late 80's, and early 90's, I had the task of keeping the slobbering pigs turning! We had one with a Cummins, and that engine used little or no oil and was quiet compared to the Detroits. Hearing protection was a must. The compressors were used to make snow. At any given time when the demand for air was at its peak, we were capable of pushing out 10,000 Cubic Feet of air per minute at 100 PPSI. Dandy Dave!

[joe_padavano]

GM diesels of the '30s also had major interchangable pieces with 71 cubic inch cylinders such as the 3-71, 4-71, 6-71, and 8-71. All were 2 stroke supercharged diesels. 6-71 superchargers are still popular on top of hemis.

This is a common misconception. The Roots blower on the GM 71-series diesels was NOT a supercharger, it was a scavanger pump mandated by the two stroke design. Yes, hot rodders have converted these pumps to be used as superchargers on gasoline engines, but in their original application they were not used that way.

[R W Burgess]

.......... it was a scavanger pump mandated by the two stroke design. QUOTE]

The difference between a scavanger pump and a supercharger please???

[Guest Oracle]

Detroit Diesels first 'landed' here in 1940 when the British Admiralty contacted GM and commissioned them to trial 6-71 engines I think it was, in patrol boats. They ended up being used in pairs in Valentine tanks for example.

[Guest Bob Call]

Wayne, et al

A quick explanation of what Joe said about the roots blower on GMC/Detroit diesels being a pump.

As you know these were 2 stroke cycle engines. Normally a 2 stroke has the intake connected to the crankcase and uses reed valves to prevent backflow from the crankcase to the intake manifold and carb. On the up stroke of the piston the air fuel mixture is drawn into the crankcase. The down stroke of the piston compresses the airfuel mixture in the crankcase and when the piston is at the bottom of its travel it uncovers intake ports in the cylinder and the pressurized air fuel mixture flows into the cylinder and charges the cylinder for the next cycle and forces the spent exhaust gas out of the cylinder.

The GMC has intake ports near the bottom of the cylinder and an overhead poppet exhaust valve. The GMC does not take an air fuel mixture into the crankcase, it has an air jacket connected to the intake ports that is open to the atmospheric pressure and a fuel injector nozzel at the top of each cylinder. So, at this point with only atmospheric pressure no matter how long you crank the engine with the starter there is no air flow into or out of the cylinder. Thus the roots blower is added to pressurize the air jacket and force air into the cylinder to be compressed by the piston and fuel injected for compression ignition. The pressurized air being forced into the cylinder by the roots blower also forces or scavenges the spent exhaust gas out the exhaust valve.

The stock GMC roots blower is not real efficient as a supercharger. Thus most professional racers use aftermarket roots blowers that are designed as superchargers and are much more effieient as an air pump. Because the GMC 71 series roots blowers were so widely used by racers the aftermarket manufacturers used the GMC case sizes in their products so their blowers fit manifolds made for GMC blowers. Back in the days of the flathead Ford V8 the 3-71 and 4-71 were the most popular sizes for hot rodding. When the OHV V8's came on the scene in 49, 50 and 51 it was quickly realized these bigger better breathing engines could use the 6-71 and it became the standard. In the early 60's as stroker engines became the norm with racers the 8-71 gained favor. The next step up was the 12-71 and 8-92. Then more efficient custom built and aftermarket blowers. Now the movement is to turbochargers as they are powered by exhaust gas, energy that is wasted on a roots supercharged engine. It takes a lot of horsepower to spin a race preped roots blower and by using a turbocharger that power is put into the drive train.

Edited December 9, 2011 by Bob Call (see edit history)

[Guest Dick Whittington]

I spent the Summer of 1969 doing archaeology in Israel and was amazed that nearly ALL the taxis were Mercedes diesels. Did anyone ever have an Olds diesel that was actually reliable and long lived?

I worked for a fairly large fleet during that era, involved with purchasing and maintenance. We bought 10 vehicles with the 350 diesel. We ran a couple of them over 200k with only normal maintenance, and then there were the ones that could not run 20k without major maintenance. Seems the key to longevity was keeping them on long trips. The two high mile engines were driven 1,000-1,200 miles a week. The high maintenance engines were used for short trips.

We were a predominant Cummins fleet, but would buy 5-10 trucks every year or so with either Detroit or Clatterpillar engines. One of the faults with the 71 series was fuel economy (forgetting the oil leaks). They would be .2 to .7 mpg under the Cummins. The Detroit had too many more parts that could break vs either the Clatterpillar or Cummins. Cat was/is way more expensive to work on than either of the two other makes. The latest emission standards have forced Cat to abandon the highway engine market. The last engines were fuel hogs, extremely complicated, hard to repair, and over priced.

[rocketraider]

Seems the key to longevity was keeping them on long trips. The two high mile engines were driven 1,000-1,200 miles a week. The high maintenance engines were used for short trips.

Everyone I knew who got good service out of the 350 GM Diesel drove it far enough every day that everything got completely warmed up- at least 25-30 mile trips one way. These folks also understood Diesel maintenance and had installed extra fuel filters and water separators.

The latest emission standards have forced Cat to abandon the highway engine market. The last engines were fuel hogs, extremely complicated, hard to repair, and over priced.

Amazing how we've managed to shoot ourselves in the backside, innit?