There’s a reason this 1950 GMC truck has such a swollen hood: It’s covering up a giant Detroit Diesel 6-110 engine, designed primarily for marine, military, industrial and railroad use. Although not originally intended as a highway truck engine, it was installed in three prototype 1950 GMC trucks, one of which was leased to Pacific Intermountain Express to gain experience with it in regular use. With their raised and elongated hoods and correspondingly higher cab, they were certainly formidable looking, and with 275 hp they would have offered direct competition to the similarly-powerful Hall-Scott 400 series gas truck engine.
But no further units were built, as there were a couple of issues, which were deadly in this application.
The 6-110 was created in response to the need for greater power that didn’t require lashing together two or more 6-71s, for high-power demands in marine, military and industrial settings. It arrived in 1946, and like other DD engines, its number referred to the 110 cubic inches per cylinder, for a total of 660 cubic inches. In principle, it was essentially a scaled-up 6-71, and shared certain key components like the unit injectors, governor and marine reduction gears.
There was one big (and fatal) difference: instead of using the tried and proven Roots type blower as used on all the other DD engines, GM decided to use a centrifugal blower, located right above the flywheel.
Here’s a rare surviving example of a 6-110 with that type of blower. From a knowledgeable comment left at a forum post:
The original 6-110’s were produced with a rear mounted centrifugal blower, which was driven at a 13:0.1 over-driven ratio which was fine for constant rpm applications, or as used in Budd RDC’s (Rail Diesel Car) where they were governed at a maximum of just 1,600 to 1,800 rpm and no chance of over-speed above 2100 rpm (crank speed). As used in mining / haul trucks and governed at 2100 rpm…. they would not tolerate ANY amount of over-speed conditions without the compressor turbine in the centrifugal blower disintegrating and sending fragments into the engine.
Furthermore, the blower drive gear and shaft were undersized, and failed commonly, especially in situations where the engine speed varied often, as would be the case in a highway truck. GM tried reducing the blower ratio to 11.0:1, but that did not create enough draft to properly evacuate the two-stroke cylinders and led to smoking.
Here’s a few blurbs from the time.
These issues were not as fatal in other applications that saw more continuous duty. The 6-110 found favor in marine use as well as in powering the Budd RDC self-propelled rail cars, as seen above, which used two of the 275 hp units per car. The centrifugal blower is quite visible, on the far end of the block. These RDC engines each fed a torque converter, which allowed shiftless speed up to 85 mph. The RDC was a rare success in its field, allowing railroads to downscale their shrinking passenger operations prior to the creation of Amtrak. A number of them are still in service.
In around 1951, the 6-110 block was redesigned to use the tried-and-true Roots blower, as seen here in this one being run up. In this case, the blower is exceptionally noisy, because its air intake is wide open, without any air cleaners and their plumbing.
Presumably the Roots blower version would have been much better suited to over-the-road trucks, but apparently the experiment of installing the 6-110 in trucks was deemed unsuccessful in other ways too, and not taken up again.
As a frame of reference, here’s what a production heavy duty GMC diesel truck looked like at the time. It came with either the 4-71 Detroit Diesel “Jimmy” as in this truck above with five bars in the grille, or the 6-71 inline six was rated at 165 hp in 1950, which was on the high end in terms of powerful diesels of the time (six bars in the grille). GM steadily raised the power of the 6-71 in the 1950s, until it reached 238 hp, and eventually 285 hp when it was turbocharged.
What really killed the 6-110 was the arrival of the larger V versions of the -71 family arrived, with the 8V-71 offering 318 hp and up to 360 hp when turbocharged, and of course the even larger 12V-71, never mind the V16 and V24 versions. The 6-110 did continue on until 1965, and with turbocharging eventually made some 350-360 hp. Its production ended in 1965.
The 110 was essentially replaced in 1967 by the 149 Series engines, made in V8, V12 and V20 configurations. These were typically used in mining, marine, generation and other related applications. They were built until 1999, and their power was steadily increased through improvements in their turbocharging and electronic engine management systems (DDEC). The final version of the 20V149 made 2,936 hp (in standby generator use) from its 2,980 cubic inches, an impressive feat for a large diesel.
I’d like to imagine this PIE truck duking it out with a Hall-Scott gas engine truck on a long grade somewhere out West.
Related reading:
Hall-Scott 400 powered Peterbilt Hauling Giant Load of Logs
1951 Kenworth With 600 Hp Hall-Scott V12 Engine – The Most Powerful truck Of Its Time
Trackside Classic: Budd RDC Railcars
Very, very interesting history for me, the old truck guy salesperson. You mention the “71” series. Near to where I live in the Hudson River Valley, a stone aggregate company had 12V-71`s in tractor service. One day I was sitting under an EL in The Bronx (elevated subway line0 working on paperwork in my car when the 12V-71 turned around the block several times in perhaps fifteen minutes. You had to hear the reverberation! OUCH! But what a strong engine!
Only saw one of these 6-110’s in my career, it sat outside the local DD shop for a few years, a dead genset. Detroit Diesel had blower driveshaft problems on all their 2-strokes. It was not uncommon. The 92 series was the worst in its early years as the drive was the same size as used on the 71 series. The splines would strip and there you sat. The first fix was a hybrid shaft with a “coarser” spline on one end and a new drive plate to match. The factory fix was the new spline configuration on both ends. The final change that also helped was the by-pass port blower. That also reduced the strain on the shaft.
I never saw a shaft with the coarser splines on both ends fail.
The usual fix was it stall a new shaft and drive plate and off you went. It usually was a quick fix and all was good. Once in awhile you would get bit and the repair you made failed. The spline hub in the blower had a “cushion” drive feature that was a double cam lobe shaped splined piece that nested in between two packs of thin spring steel leaves. If these leaves had started to fatigue and breakdown small pieces could escape out of the hub and get in the gears and lock up the blower. That failure seemed to happen more often on the 53 series, possibly because of the higher RPM range or my other thought was the 4-53 and 6-53 series blowers had straight blower rotors rather than the twisted rotors of the 71 and 92 series. More pulsation with straight rotors? The 4-53 turbocharged one in the medium duty Chevy/GMC trucks were the worst as you had to pull the blower to fix a stripped drive shaft. At least with this one you could be sure to fix it by replacing the shaft and both the drive hub and driven hub.
Ah the good old days, Dr. Detroit always had patients to treat. Green paint and black oil stained hands.
Well well. Am on a number of Israeli trucking history forums and FB groups. For many years a rumor about a GMC truck with 275 hp kept popping up on the above; this beast was apparently imported sometime in the early to mid 50s. I initially discounted it as an old timer confusing a 238 hp 6-71 with the 6-110 but then the below (via Yehuda Tzafreer) popped up…
I ran into that too, at an old truck forum. How did it end up there? I would have assumed GMC would take it back and dispose of it eventually. I wonder if it had the Roots blower. And if this was possibly a home brew job.
Paul, the person who first mentioned this is unfortunately no longer among the living and I could not find out any more information, so I do not know. GMC imported quite a few heavy trucks into Israel in the 1st half of the 50s but again the dealer has changed hands at least 4 times since so the chances for any lists with chassis numbers are slim to non-existent. I doubt it was locally modified. My suspicion is that someone (judging by the picture, the Dead Sea potash mining operation) needed something powerful to get through the ascent from the Dead Sea to the Negev desert and maybe GM thought it would make sense to send over one of the beasts (or a later one) to an obscure market where failure would not be detrimental to sales (as the case would have been in the US). I can try and ask again, maybe someone will pop up with additional info…
I remember a lot of Pacific Intermountain Express rigs out here in California.
Yes ~ I too remember seeing many P.I.E. rigs .
Interesting engine and failure point .
-Nate
Interesting 1953 SAE essay by Caterpillar guy; the 110 engine mentioned only in passing, but lots of discussion of particularly Western issues (a slow mountain ascent costs time, which costs money, etc.) and such. I’ll post first two pages here, but could add the rest if of interest:
(page two)
My dad worked for P.IE in Richfield,Ohio . I worked on 71 and 92 series Detroits for 20 years in the 80s and 90s. I rebuilt a lot of them.
Sou do Brasil !
Meu pai era agente da GM em Santos litoral de São Paulo.
Haviam poucos 6-71 em caminhões a maioria era 4-71.
Tenho miniatura de 6-71 que a GM deu a meu pai.
Se algum colecionador tiver interesse meu email é valdirlodycla@gmail.com
We still run a 6-110 in a allis chalmers dozer it’s a HD20
PIE was Pacific Intermountain Express, my father drove for them , back in the 1960 ‘s
My Dad worked for P.I.E. out of Denver.. Local driver.
The photo above of the GMC tractor hauling the pipe load isn’t an entirely correct comparison to the special P.I.E. tractor. It is of a late ’49 or 1950 HDC or HDCR-740 or 750 model which was powered by the 4-71 diesel. Its appearance is representative of all 700 and 800 series models at this time, having five grille bars. The starting point for the experimental 6-110 powered trucks was the 6-71 powered 900 series, with six grille bars. The experimental trucks had one bar added to the grille (for a total of seven) with the hood and cab raised by the same amount. They even kept their standard model number of HDCW-954 (950 series) as all of that nomenclature still applied to these modified trucks. This photo is of a standard production P.I.E. HDCW-954 of which they owned many.
Thanks for the clarifications. I’ll amend the text.
Here is another photo of a production (“normal”) 900 better illustrating the 6-bar grille and standard height hood sides and cab, to compare to the experimental P.I.E. tractor. This one happens to be a model HDC-903.
We have three 6-110 running in our tour boats. They were built in 1955, 1957 and 1959.They have run all day every summer day since new. They are all three original to the build. They overhauled the two in the 80s but one has never had the pan or head off. We do not abuse them rarely over 1400 rpm and we change oil about every 200 hours. I have replaced injectors and that is about it. They ran today and will tomorrow. If I were offered new engines today I would want a 6-110. To see the boats visit Original Soo Locks Boat Tours
740 Detroit I believe it’s the 6-71. Will verify. Can anyone tell me more about this truck?