1956 GMC PU Engine ID

[Guest schmuck281]

I have a 1956 GMC 100 1/2T V8 pickup. I bought it from a dairy who had bought several in 1956 and went out of business in 1988. I did a little work on it and drove it for a work truck until 1994. I have had it garaged since. Now my son is showing interest in restoring or hotrodding it.

From what I can find out, they put Pontiac 316 V8s in those. The engine that is in it looks correct. But the dairy cannibalized the other pickups over the years until there was only the one left.

I would like to make sure the engine is the Pontiac and not one from another later model GMC. Where are the engine numbers located and where would I find a list to decode it?

It had a Stromberg WW carburetor and the oil bath air filter when I got it. (unfortunately the carb didn't survive). It has an open crankcase and the valve covers are plain with GMC stickers.

Any help in IDing it would be appreciated.

[PONTIAC1953]

hi, i don't have numbers to give you, but we have guys in the pontiac1950s group in yahoo groups that can help. the engine pictured is a pontiac built gmc V8, and in 56 gmc listed it as a 317, but it is a pontiac 316. charles coker, 1953 pontiac tech advisor, poci.

[Guest schmuck281]

Thanks for the help. Was 1956 the only year this engine was used, or was the Pontiac engine used in other years as well?

[Guest Bob Call]

GMC trucks in 55 and 56 used Pontiac V8's. Hollander interchange shows them to be 288 and 316 cubic inch. 57 thru 59 used Pontiac 336 and 347 cubic inch. In 60 GMC had its own V8 and V6. The Hollander doesn't list it but I know from personal experience that GMC also use 324 cubic inch Olds V8's. Back in the 50's I used to buy plain rocker arm covers with no name to chrome and use on Olds engines. Also bought flywheels, clutches, throwouts, etc. to convert hydramatic Olds to manual trans. Bought all this stuff at the parts counter of the local GMC truck dealer.

In the early 60's GMC had a V12 based on its V6. The 12 cylinder block used two sets of V6 heads.

Large 55 thru 57 Chevy trucks used Buick 322 cubic inch V8's until the Chevy 348 came out in 58.

Edited August 31, 2009 by Bob Call (see edit history)

[Guest schmuck281]

Thank you for the info. Is there a way to tell the Pontiac 316 from the Pontiac engines used 57-59?

The reason I am asking is that on the fan hub is painted "59 GMC #2466".

It looks like an old junkyard tag but I don't know if it is referring to the engine or just the fan.

So is there something that would tell me definitely that this is a 316 and not one of the later engines?

[Guest Bob Call]

The 246 on the fan hub is the Hollander interchange number for 55 thru 59 Pontiac and GMC V8 water pump assembly.

Post on the Pontiac forum at this site or a Pontiac specific site on the internet the engine number. One of the Poncho experts should be able to give you the cubic inches from that number by tieing it to a specific year. The 288 was the 55 passenger car 287, the 317 was the 56 passenger car 316 and the 347 was the 57 passenger car. I don't recall the 336 as being a passenger car size, but, I could be wrong. 58 and later big passenger cars were 389 and the 60's LeMans V8's were 326. 58 and later high performance engines were 389, 421, 428 and 455.

Pontiac V8's from the 247 thru the 455 are quickly indentifiyable by the concave (curved) lifter valley cover and if the cover is missing the ends of the valley in the block are curved.

There is lots of hod rod stuff for Poncho V8's. Poncho guys at Pontiac sites can guide you to sources for parts. Most stock parts are available at www.rockauto.com

Edited September 1, 2009 by Bob Call (see edit history)

[Guest schmuck281]

Thanks for the info, Bob. Could you tell me where the engine number should be located? I haven't been able to locate anything.

[Guest Bob Call]

The engine number should be on the front face of the block on the right side just below the head. May be hard to see under the generator. Get a flashlight and wire brush and start looking. On cars with low compression engines there is an L in a circle following the engine number. Truck engine is most likely a low compression. On cars the engine number and the car serial number on the driver door post are the same. I don't know about trucks.

[Guest schmuck281]

Thanks again for your help Bill. That's exactly the info I was looking for.

[Vikingmarine13]

I have similar questions.  I have a 56 gmc big window long bed and I'm trying to identify the engine. The ol boy I bought it from believed it  was a 400. I ran the block numbers and several sites tell me it is either a 355 or a 389. But when I run the numbers on the head/ exhaust manifold it comes up as a 316. Also the truck has its hydrostatic auto. Any help would be appreciated