The Stovebolt Site Forums The Shop Area Engine Shop GMC 336 Heads - Interchangeability?

Well guys, the machine shop called me today with bad news. A while ago I had pulled the 336 V8 out of my '59 LWB to have it rebuilt... it ran, but leaked oil, had a burnt intake valve, and low compression. The machine shop has thus far cleaned and bored the block, as well as located all the parts for me to reassemble the engine...

The call came yesterday that BOTH of my heads were cracked, and not in good places as the cracks were on both heads into the
valve guides, so they can't even use the heads I've given them.

Now, the challenge comes of finding some good heads off of another GMC 336 (which I think will be like trying to find the holy grail) or to find out if anybody knows what the interchangeability is off of other Pontiac engines of the era.

The only thing I know is that engines such as the 350, 389 and 400 used a later style head and intake assembly, where the water jackets do not come out of the front of the heads.

Has anyone had any experience with this? Is it possible or am I dreamin'?

According to my GMC Master Parts Book, there are 2 different heads for the 336. Prior to engine s/n 33635001 it used head #530377. Effective s/n 3365001 it used #533777. Also the heads from a 288, 316 and 347 are different part numbers.

How to determine what the difference is would be anybody's guess. The book says "Includes plugs & studs" so I bet these part numbers won't match the casting numbers on your heads. It may be the castings are the same for both 336 heads, maybe not.

As far as using Pontiac heads, I'd bet they would work but can't say for sure. Hopefully there's a Pontiac man on board who can help you further.

From my 1965 Superior Interchange Light Truck manual on cylinder head interchanges:

#530377 GMC early S 8-336 (to eng #336-35001)
Pontiac '58 except 3 carbs with 2 barrels each and fuel injection.

#533777 GMC late S 8-336 (after eng #336-35001)
Pontiac '59 w/o 3 carbs with 2 barrels each.

Also not sure of differences. Hope this helps.

Thanks guys,


....than am I to understand that the heads off of a '58 and '59 370 Pontiac (without tripower) are directly interchangeable if not exactly the same? A little research on google about the GMC 336 gathers that the 336 was in fact an underbored 370 Pontiac. Also, after looking at some pictures I see that the 370 does in fact have the water jackets coming out of the front of the heads like my 336, while the "upgraded" 389 from '59 and up looks completely different.

I'm really crossing my fingers on this one... 'just got to find someone willing to give up a pair!

Call Dennis Waldron at Waldron Auto Parts, LaVergne, TN. 615-793-2791. If he doesn't have an old Pontiac engine like that, he can probably steer you to someone who does. His salvage yard has been in business since at least the late 1950's, possibly longer.
Jerry

Fantastic, thanks for the tip Jerry, I'll ring him up Monday.

I'm talking with a person whose got a v8 that came out of a 58 GMC, but whose head casting numbers are 528511... any of you have any clue what kind of engine this is? Is this an "early" '58 336?