This vintage snapshot of a Chevy gasoline powered semi truck is rather fascinating, as it’s a medium-duty C60 with a sleeper cab in the role of a big semi truck. It did have a bellowing 427 V8, which had plenty of power, but wasn’t exactly fuel efficient (2 mpg at full chat?). This rig is something of a throwback to an earlier era, when medium-duty trucks with gas engines were quite common as semi trucks. But by this time, that was not so much the case, as heavy duty trucks with diesels were increasingly dominating the semi truck market.
Almost certainly this truck wasn’t in typical full-time long haul use, but more likely hauling perishables from farm to wherever, probably seasonally. Who knows for sure?
The medium duty series topped out with the C60, and in 1968, a new 23,000 lbs rated rear axle allowed a GCW (Gross Combined Weight) of 60,000 lbs.
I should point out to those not in the know that the 366 and 427 Chevy Mark IV truck V8 engines were not exactly the same as those used in Corvettes and such. The biggest difference was that these were tall deck engines, meaning the block deck height (top of block) was higher, so that longer pistons with four piston rings could be used. That improved durability at the constant high loads these engines were subjected to.
These are referred to as “tall deck” 366s/427s. And there’s other differences of course too, from sodium filled exhaust valves to heavy duty components all-round, and of course the accessory drives are set up for truck use, for air compressor and such. The Holley four barrel has a governor, which works off the mechanical advance distributor, limiting max. revs to 4000. These were of course tuned for maximum torque and continuous power output, and at full chat, exhaling through two big short pipes, they were somewhat famous for their vocalization. And their prodigious thirst.
But with a real 230 hp on tap, as much or more than a DD 6V-71, they could move a load right along.
That generation of C60 along with the companion GMC 6000 series was popular for school bus platforms…..The school district where I attended school in the 1970’s had a whole fleet of GMC 6000 buses with Thomas and Wayne bus bodies and with the GMC 351 V6 medium duty truck engine.
They were from the 1970-1973 model years and were replaced in the fleet by International S series buses by the mid 1980’s.
The buses used this front end until the mid-80s, no idea why.
I would also be interested in knowing why. I’ve seen in brochures and commercials the Chevy’s school bus chassis used the prior generation GM medium duty front end and made me wonder.
Speaking of school bus platforms, I remember then GM kept the old 1967-72 front end until the early 1980s for school bus. https://en.wikipedia.org/wiki/Chevrolet/GMC_B_series
I used to drive a 427 equipped C60 hauling corn silage. It was a single axle but it had a stack of Springs under it with a 5 speed with a two speed axle. Corn silage is heavy but that truck went like a scalded cat empty or full.
Worked on many of these back in the day. Pretty reliable beast and much better than the 350 small blocks that were also used, more like abused, in the medium duty trucks. In the later years you could get a 454 if you really needed to burn some fuel. One other minor difference between the car engine and the truck engine was an additional bellhousing bolt at the peak of the bell housing. The transmissions were not supported unless you got the mini-road ranger trans so there was a fair amount of weight cantilevered of the bellhousing. The additional bolt provided additional support. Every once in awhile you would see a pickup engine dropped in and if the bolt hole wasn’t added it probably wouldn’t be too long before the tranny had worked things loose. As you can see the air compressor was a real hunk of iron that tended to shake apart if you didn’t stay on top of belt adjustment and proper assembly torque for the mounting bolts. There were a few odd problems here and there but generally if you kept them tuned up and did the maintenance this was a good engine.
Xr7, I got cozy with quite a few of these too.
Do you remember this one? …some had the transmission-to-bell bolts threaded into the bell. Others had the bolts threaded into the trans, and accessed only from “inside” the clutch housing. I believe the former was Chevrolet and the later GMC. Now I’m not exactly positive on the rhyme nor reason, but I definitely recall the anguish.
In the truck, some of the “backwards” bolts were very difficult, or impossible, to access for the usual method of disassembly. Pulling the bell with trans brought another host of issues.
I remember that well! Usually, the 2 bottom transmission-to-bell housing bolts threaded in from the clutch side. I also remember at some point they moved the air compressor from the high location on the right side to a lower location on the left. Didn’t come loose, belt stayed tight, but it made changing #1 and #3 spark plugs tough. Around that time they also came up with a high mount water pump for the 366 and 427. Didn’t leak very often, but must have weighed 40 lbs.. That was a fun job too.
What I do remember about that high mount water pump was the spectacular failures. Its main problem was driveline vibration or engine vibrations. The pump would crack and separate from the engine dropping the spinning fan into the radiator and fan shroud. I wish digital cameras would have been around. the pictures of the carnage of medium duty trucks was really something. We attributed the carnage to the operators not being trained and usually not paid very well. If the truck ran and it moved, just keep driving it. It was amazing the stuff that was brought in to have a look at, usually started with ” there might be something wrong with it”. I had one come in on the hook, the engine had gotten so hot it the upper radiator inlet solder melted and the inlet came out. That’s burning down the house. Another was brought in for service, a G van, oil change and lifter rattle, pulled the plug to drain the oil, before I hardly got the plug out and set it on the floor the oil was done draining, got maybe a quart in the pan. Well, now what? Pulled the filter, no obvious debris in the cut open filter. Fill it with oil, slap on a new filter. Fire it up and the rattling lifters quiet down a a few seconds. Customer says he will run it for now. I’m figuring he will be back for an engine or another vehicle in a few months.
I do have to say I loved working at a dealership, more variety of work than a fleet operation. Only exception was the DOT fleet. Now your talking variety, I worked on stuff I never could have imagined.
Thanks for mentioning the bolts that had to be pulled from the “inside” I forgot about those. IIRC I think I had a specific 12 point socket and breaker bar combo that I used to break the bolts loose as there wasn’t any room to work with. Special tools were the bain of the business, hated buying them but the time and frustration they saved was worth it. There was one other trick when doing a clutch job on these things. You couldn’t get the clutch out of the bottom of the bellhousing because of the frame crossmember. Some people torched the crossmember for clearance, others pulled the bellhousing. However what worked for me was I would use a crowfooot prybar to install a 1/2 nut between the clutch release levers and the clutch cover of the pressure plate assembly. This would retract the pressure plate enough so the assembly was now “thin enough” to slip out past the flywheel and crossmember leaving the bellhousing in place. If everything went right you could do a clutch job on one of these in an hour. One of my buddies did one in 40 minutes. It was the perfect set up, Shag tractor with air brakes. Nothing in the way.
In the later years you could get a 454 if you really needed to burn some fuel.
The 454 was never offered in tall deck truck form, and therefore not available in the medium duty trucks. In fact the 454’s rep in RV use had a rather spotty rep, as it wasn’t a genuine truck engine.
You are correct, I thought we had a truck with the 454 in it but it must be the cobwebs getting tangled up again.
Hi Paul, my Dad, Russ Larson started Polar Chevrolet back in the 60’s. I am trying to gather any and all Polar Chevrolet memorabilia from the mid 60’s – mid 70’s when my Dad owned it. If you know of any, please contact me at rlarson@larsonclaims.com Thank you, Rick Larson
Sorry; can’t help.
I have a 1968 C60 Dump Truck that had a 327 in it. The blew a rod and now I’m trying to put a 366 in it but horse shoe motor mount isn’t lining up. It’s sits too far forward. Does the 366 use different motor mounts or is the bell housing used with a 366 different? I appreciate any help you can provide on this. Thanks in advance!
Almost certainly the motor mounts are different. As to the bell housing, I assume it’s the same. Did the engine bolt up to the housing?
The deck height on a standard BBC is 9.8″ while the tall deck was 0.4″ greater at 10.2″. It’s no different than a Chrysler B series vs RB, or a Ford 302 vs 351, or Olds Small Block vs Big Block, etc. However, the tall deck BBC was only used in HD applications and not passengers cars. The tall deck BBC was formerly used in as the basis for high performance engine builds prior to modern aftermarket blocks being released. These blocks had a reputation of being able to handle a lot of power and abuse. Of course, being a tall deck caused fitment issues due to the extra width and height. The large 4 ring pistons and cylinder heads were not good in performance applications vut they could be replaced easily. The extra width meant the need for tall deck intake or spacers for a standard BBC intake. Today, GM sells it’s 572 engine, which is tall deck BBC, albeit a later Mark of the BBC.
I never drove a 427 in a GM medium duty, but those that I knew who did always stated the same story Paul states – lots of power and very thirsty. I drove several 366s and they weren’t overly powerful but seemed to take a lot of abuse without complaint.
GM crate engines are just awesome and are a fantastic value. There is absolutely no sense in rebuilding a tired 350 when you can get a new 350 crate engine for $4000 CDN. That’s for 300 hp. Building your own engine would cost more and the crate engine is new.
I’m just so amazed that the Small Block Chevrolet is still being manufactured after 66 years. It has to be a world record.
https://www.chevroletperformancestore.ca/product-page/350-ho-base
Those Chevy/GMC ‘ME65’ series gasoline tandem trucks were quite popular as 8 yard dump trucks. A few like this ended up as tractors, mainly for short distance heavy hauling. Interesting that GM kept producing the Big Block/tandem rear axle configuration through the next two generations of medium duty truck until 2002. They were probably the last to build gasoline powered tandems.
Curious, why did GM use two different conventional cabs in medium duty trucks in the late 60s early 70s? I forget the name of the other cab platform but it was featured as a car hauler a week ago or so.
You mean this one? It was a GMC cab, for their medium and heavy conventional trucks, and also shared with Chevrolet for their some medium and heavy conventional trucks. And GMC also used the Chevy cab for its low-end medium trucks. There was some overlap, but that’s just how it was with Chevy and GMC.
That’s right. The ‘GMC’ cab (H and J series trucks) was slightly larger than the ’67-’72 light truck cab, but similar in design. The H/J cab came out in ’66, a year before the new light duty cab. From ’66 to ’68 GMC used the larger cab on all their domestic 4500 series and larger trucks, but the cab was also used on some of the larger Chevy’s.
I wonder how long it will be until we see a meaningful number of gasoline engined medium duty trucks again. It might make sense to team Ford’s new big block with a proper multi-ratio manual transmission in something with a GCVWR in the Class 6 or even Class 7 weight range. Gas is cheap. Labor to fix complicated current diesels is expensive.
The F-650 and F-750 are available today at your Ford dealer with the 7.3 gas V-8.
New gas V8s make sense for fleets, but manuals, not so much.
Ford has been making big inroads in the medium duty market since the 2016 redesign, and a lot of that has been through sales of gas trucks. Back then it was the 6.8 liter Triton V10, but it’s the 7.3 liter big block V8 now. They’re the only gas trucks in the segment right now, and they’re selling for precisely the reasons you’ve mentioned – the fuel is cheaper and so is the servicing.
I don’t understand why GM isn’t trying to compete with the medium duty Silverado by putting in their new 6.6 liter gasser. That truck is diesel only for some reason.
https://www.trucks.com/2019/07/22/ford-international-gain-truck-share/
I’m really hoping for everyone’s sake that the Godzilla V8 is better than the Triton V10. When I ran a shop, I would get phone calls of symptoms and be able to tell the customers what they drove. I was also right about the additional problems that they didn’t mention 100% of the time. Tritons had timing chain issues, cracking exhaust manifolds combined with mounting studs that snapped every time, and coils went like popcorn popping. They’d be fine for years and then all of them would fail as fast as the customer could decide to change one and hope for the best. Just one of the worst engines of modern times not made by Subaru or VW.
Lots of tow trucks and service bodied medium duty Rams and Fords seem to be gas lately. Passed Ram 3500 with a couple cars on a trailer on the NJ turnpike earlier in the week and noticed a 6.4 badge instead of Cummins on the truck.
One nit… wasn’t ’67 the introductory year?
It was. But without the 427, which came along in ’68. At least according to my deep dive. Plus, this has to be at least a ’68 because it has the side reflectors.
Like Paul and every other red-blooded lead foot, I put many of the “Corvette of trucks” through the stress tests. Once a buddy and I were running circuits with dump trucks. He, mighty 427 and 5-speed, with beautiful chrome “gills” on the hood and windshield trim. Me, lowly 350, 4-speed w/2-speed axle, plain flat paint. After tipping we would do our best to line up to find the champ. It would be as intense of a side-by-side engine screaming gear-jamming match as anything you saw at The Nationals.
We couldn’t find a decisive winner.
The quick wind-up and initial fast axle shift of the 350 started out with an edge over the “heavy” 427 and its required slow spin-down at shifts. Then the 427 would come on strong once it was pulling again and getting into its sweet spot. Repeat. Finally at the top the 427 would run out of gear before the 350. I know, we were rotten. LoL
Where I live in Vancouver, British Columbia I’d say at least 90% of the waste management fleet is running on CNG. All the city buses are running on it and even BC Ferries runs on 80% CNG and 20% diesel. It has made a significant improvement nn local air quality in the downtown core.
I am seeing more and more CNG units since they are much cheaper to run that diesel and all the DEF and soot filters are gone. These vehicles often spend a fair bit of time indoors and the CNG fuel is perfect for that.. Finally, the engines are very quiet. The drivers love them.
Wow, so cool. I remember as a child my father took me to Polar Chevrolet, in White Bear Lake Minnesota. In the showroom was a functioning display of a 427 Chevy truck engine connected to a 5 speed manual transmission. The whole thing was powered by a slow moving electric motor. It had cutouts of both the engine and transmission. You could actually push in the clutch and shift the gears and see them change gears. 9 year old me thought that was so cool!!
I almost forgot to comment on the truck in the photo. Looks like a really proud owner’s truck to me, good looking truck, very clean, lots of nice details on it. One fairly rare thing to see is the disc wheels, cast spokes were the norm on these. The one big improvement coming on the next gen medium duty was the option fiberglass tilt hood. That made service and repairs SO much easier.
Thanks Paul, keep the truck posts coming.
The guy in Victoria who worked out how to get the best fuel consumption and performance on LPG did his experimentation with one of these Chevrolet trucks his methods loewered consumption without losing performance and the truck ran fully loaded
I own a 1968 C60 truck with a 327 and an automatic transmission in it. Has anyone seen that combination before? I’m currently rebuilding the engine and was suprized to find a forged crank in it. It has a short dump bed on it on a longer truck frame. Looks like enough room for one of those sleepers they came with.