[Schurkey]

Does anyone remember details of the Pontiac engines used by GMC?

In '55, they used the Pontiac 287 (but called it a 288), in '56 they used the 316, and in '57 they used the 347. Wikipedia lists two different 336 engines from '58 and '59:

GMC's own V8 was the 336 in³ (5.5 L) OHV/pushrod engine. It used a 3.875 in (98.4 mm) bore and was produced only in 1958 and 1959.

While both the '58 and '59 GMC V8 engines were advertised as 336 in³ (5.5 L), the '58 version was based on the Pontiac 370 in³, but with a smaller 3.875" bore giving a 336.1 in³. The '59 version was based on Pontiac's 389 in³, but with a smaller 3.78" bore giving 336.9 in³.

source: http://en.wikipedia.org/wiki/GMC_V8_engine#336

1. Can anyone verify the two different 336 engines?

2. Anyone want to dispute or add to the information above?

[Pontirag]

only the very vaguest recollection.....Why?

actually, there were two different 336 engines. "toned" down a little from the 348's. not sure which was which but I believe the difference was in one year they destroked the motor and in another year they reduced the bore. Dont really know alot about that new stuff. Your info seems correct.

[Jack Gifford]

Wikipedia's got it right (this time!)- '58 336 was a small-bore 370, and '59 336 was a small-bore 389- actually closer to 337 c.i., as Widipedia said. The rest of the engine was pretty much identical to the cars, except for lower compression ratios- I think dished pistons, but haven't actually seen the inside of a 336. Strictly 2-bbl carbs, and I'm guessing a milder cam. Wasn't the '56 engine (cars and GMC) actually 322 c.i.?

My '59 GMC had a 336 from the factory, but it was long gone when I bought the truck. It will go back together with a Tri-Power '58 engine at 382 c.i. My front fender "GMC" emblems were too pitted to use, so I decided it really ought to say "Pontiac V8" anyway!

Over on the "61 & Older" forum, there's quite a lot of discussion of Pontiacs in GMCs.

[Schurkey]

Originally Posted by Pontirag

only the very vaguest recollection.....Why?

Because I'm trying to track down a rumor of Olds 370 (actually Olds built a 371) engines being used in GMC trucks. So far as I can tell, the rumor is false. I think the truck series number was 370, not the engine displacement--and finding out that the 336 was developed from the Pontiac 370 might have given that rumor some added mileage.

I did discover that Buick supplied 322 cid Nailhead engines in Chevy (not GMC) trucks from '56 to '59, though.

(so: Pontiac = GMC; while Buick = Chevy. Olds = Olds. Yeah, I think I've got it now...)

[Jeff Walker]

My dad wrecked out a GMC truck many years ago that did have the Olds engine in it from original. I don't recall the year exactly, somewhere between 55-57 though. Also it was a larger series than a two truck. HTH

[Stuart]

Originally Posted by Schurkey

Because I'm trying to track down a rumor of Olds 370 (actually Olds built a 371) engines being used in GMC trucks. So far as I can tell, the rumor is false. I think the truck series number was 370, not the engine displacement--and finding out that the 336 was developed from the Pontiac 370 might have given that rumor some added mileage.

This was brought up in that discussion going on in the 1961 and earlier section. Apparently the Olds engine was used in some heavier duty GMCs.

http://forums.maxperformanceinc.com/...d.php?t=547253

[Bill Hanlon]

Originally Posted by pontiac jack

Wasn't the '56 engine (cars and GMC) actually 322 c.i.?

Bore = 3.9375 Stroke = 3.25 CID = 316.59495943359375

I think the 322 rumor (for trucks at least) happened because Chevy (and Canadian GMC) larger gas powered trucks used the Buick 322 V8 instead of 265/283 engines until Chevy came out with the W engine in '58.

I like the badge layout on your fender, but what about a Hydra-Matic badge? I have 1 NOS Hydra-Matic badge with a black background. If you can find another you can have mine.

[Pontirag]

They did have the olds engines in them but they were in the larger trucks This 550 series of 1956 clearly has the old engine in it and only has 5800 miles on it.

[455Grandville]

Originally Posted by Bill Hanlon

Bore = 3.9375 Stroke = 3.25 CID = 316.59495943359375

I think the 322 rumor (for trucks at least) happened because Chevy (and Canadian GMC) larger gas powered trucks used the Buick 322 V8 instead of 265/283 engines until Chevy came out with the W engine in '58.

I like the badge layout on your fender, but what about a Hydra-Matic badge? I have 1 NOS Hydra-Matic badge with a black background. If you can find another you can have mine.

I saw an early medium (or heavy duty) Chebbie with a Buick 322 nailhead at a ATHS show,and Ive seen some Olds 324s also. Does anyone know the smallest truck you could buy a 409 Chevy in ?

[Jack Gifford]

Originally Posted by Bill Hanlon

... I have 1 NOS Hydra-Matic badge with a black background. If you can find another you can have mine.

Thanks, Bill- but I'm already indebted to you for other stuff- front mount, and ???. I thought about Hydramatic emblems, but decided to keep it to a minimum- the only "GMC" markings will be the center of the grill bar and the tailgate stamping. I've got a tiny little decal from Cal Hydro that I trimmed down to just say "Hydro-Stick"- I may put that in a corner of the rear window.

[Bill Hanlon]

Originally Posted by pontiac jack

I've got a tiny little decal from Cal Hydro that I trimmed down to just say "Hydro-Stick"- I may put that in a corner of the rear window.

It is too late to try to turn this beast into a sleeper.