GMC Colman 370

[offroadrolls]

New project, just starting to learn about these built in Littleton Colorado. Picked it up about 8 miles south of where the factory that built it stood 57 years ago.
Super stoked this thing is so cool. Look at the size of the front differential! It's got the stock 370 Poncho motor and a bit over 40k miles. It's a 2.5 ton Colman 4x4. Feel free to chime in anything you know about these or the engine.
Thanks!

 

[Torchie]

Don't know a thing about it, but I like it.
Tis a beast for sure......
Torchie

 

[falconvan]

Cool, you keeping the dump bed or going with something else?

 

[21willys]

Post a pic of the engine. Are you sure it's a 370 and not a 316? If you keep the engine I have a 316 with auto trans that been sitting. Be good for parts if nothing else.

 

[offroadrolls]

Cool, you keeping the dump bed or going with something else?

I'm going get rid of the bed and build a flatbed for it. Then I'll get either a 1000 or 1200 gallon water tank for hauling water to my house 4 miles from my shop/work. I'm hoping to use the PTO to drive a pump to pump the water out.

 

[offroadrolls]

Post a pic of the engine. Are you sure it's a 370 and not a 316? If you keep the engine I have a 316 with auto trans that been sitting. Be good for parts if nothing else.

I was reading last night that GMC used the 370 Pontiac for their trucks but had them made with smaller pistons for what I believe came out to a 316? I'd guess that was for thicker cylinder walls.
Anyway Thanks 21W I'll keep that in mind for sure.

 

[offroadrolls]

Wait!! I think it was a 336 they made from a 370 with smaller pistons[S

 

[sgtpontiac]

Gotta love the internet.... lol

Prior to developing their own engines, GMC used the Pontiac V8 engine. They used the Pontiac 287-cubic-inch (4.7 L) engine for 1955 and 316-cubic-inch (5.2 L) engine in 1956, but advertised the engines as the "GMC 288" and "GMC 316". They used Pontiac's 347-cubic-inch (5.7 L) in 1957. For 1958 and 1959, GMC reduced the bore of Pontiac's 370-cubic-inch (6.1 L) to 3.875 in (98.4 mm), resulting in a displacement of 336-cubic-inch (5.5 L). In Canada.

Clear as mud now....

 

[akatao]

I was just going to post the same info . I remember mid 70's there were some with olds engines

 

[joedoh]

imagine the smile of the guy in colorado, used to getting stuck and digging out, picking up a 4x4 dump truck and driving over everything that got in his way. must have felt like driving a cheat code. [cl

 

[jfg455]

Man that would look bad a** if you were to put a set of military MXL 53" tires on bead locks! [cl

 

[kenny c]

That thing sure looks rugged. Have you had it running yet?

 

[offroadrolls]

Yippie, I finally got this thing home. I'd been waiting for one of the local tow companies to have a big enough empty roll off coming back from Denver empty to save me a couple bucks but, I guess they've just been too busy. So I called another guy that just got in the business and he did it for 5 bills. That's 360 miles round trip in a 28000 pound GVCWR F650. I did find out it weighs about 9k pounds. We had figured it was around 7000 pounds.

So the list of stuff it needs to be road worthy is pretty long but I got started today by fixing the choke cable. Now it starts great. The kid I bought it from said he went through the carb but I noticed the accelerator pump is not spraying. So I'll need to pull the top off the carb and evaluate. I'm suspicious that the little ball in the pump bore is missing. Next, it needs a water pump bad as the bearing is totally shot. The engine is supposed to be a GMC 336 that is a Pontiac 370 with a smaller bore. The 370 is the predecessor to the 389. Anyway I went looking for a water pump on line and all the pumps listed look like they go on a pump that's an integral part of a cast timing chain cover or bolt the front of a pump housing. So heres a couple pictures of the engine. To me it looks like a bbc. Or at least the valve covers do. See what you think. I need to figure this out so I can get the w/p repaired.

 

[kenny c]

Glad yo see you got it home.

 

[studebaker59]

Best guess with the two barrel carb that looks to be a 366 chevy big block truck engine.

 

[offroadrolls]

Ya, it's got a tin timing chain cover. I always thought Poncho engines had a cast timing chain cover that also house the water pump passages.[S

 

[offroadrolls]

Best guess with the two barrel carb that looks to be a 366 chevy big block truck engine.

Thanks Stude, you called it. I can tell by looking at water pumps it's a 366 or 427, I'd assume "tall deck". I'll get the casting numbers to see if I can figure out more. Unfortunately the numbers on the pass side deck have been machined away.

 

[Bamamav]

Bud of mine has a tall deck 427 in a 58 pickup, that thing has gobs of torque and will scoot! Have to use spacers to run a regular BBC intake, other than that, I think the rest is the same as a low deck BBC.

 

[Tripper]

Wow... it's a whopper for sure!!!

BoB

 

[offroadrolls]

Today I'm going to get a look at the casting numbers to determine if it's a 366 or 427. I've been reading up on them and apparently you can easily build a 427 up to a 496. Summit has a whole bunch of tall deck aluminum intakes for it listed.