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Jul 21st, 2025 | | | | Joined: Jun 2007 Posts: 90 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2007 Posts: 90 | 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'? | | | | | Joined: May 2001 Posts: 7,440 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,440 | 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. | | | | | Joined: Mar 2006 Posts: 319 Shop Shark | | Shop Shark Joined: Mar 2006 Posts: 319 | 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.
Last edited by randy luton; 01/13/2008 6:24 AM.
"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson
| | | | | Joined: Jun 2007 Posts: 90 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2007 Posts: 90 | 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! | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | 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
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jun 2007 Posts: 90 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2007 Posts: 90 | Fantastic, thanks for the tip Jerry, I'll ring him up Monday.  | | | | | Joined: Jun 2007 Posts: 90 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2007 Posts: 90 | 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? | | |
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