637 V8 gas engine

[LEWISMATKIN]

and while dad's shop was open and in it's original location, I ran across a guy who had a 637 overhauled. He took his shaft to Graves Plating in Florence, Ala., and had it chrome plated. It was running fine at the time, but that was about '80-'81.

[bigblockv6]

Louis, a few months back I bought a set of those valves, though the seats are the same diameter the stems are shorter than the GMC valves. Evidently it would require the valve springs. This won't work with my setup since I'm running a custom ground high list cam with longer Ford 390 valve springs. The correct way for me to go is with some custom Manley stainless steel exhaust valves

[LEWISMATKIN]

how much shorter, Pete??

[2-Ton]

Yep that the engine, But the picture does not show how really big it is.
The emblem is the same as Mine has on both sides of the cab.
No pictures of the engine, but once you get past the pirate ship and skin you will see a few other GMC's that could be for sale.
https://www.flickr.com/photos/149052261@N05/

Don

[bigblockv6]

Most likely the original exhaust manifolds cracked and replacements were impossible to find so someone fabricated their own.

[bigblockv6]

Originally Posted by LEWISMATKIN

how much shorter, Pete??

I'll get the measurements out tomorrow when I get back home and I'll post some picks of both the Cat and GMC valves for comparison.

[LEWISMATKIN]

thanks, Pete!:biggring mc:

[BobBray]

Neat and very rare truck! The only gasoline powered 'Crackerboxes' were the '66-'68 FE/DE versions with the 637. To my knowledge the 702 V-12 was never a regular option in the 'Crackerbox', though it was in the L series 'Steel Tilt'. There were Toro-Flow 637 powered 'Crackerboxes' as well, I would imagine those are just as rare.

[LEWISMATKIN]

bob, some of the DW & DL did have the 702 in them. At least that is what my parts books from that era state. It was also in some of the DB cabs.

[bigblockv6]

Originally Posted by bigblockv6

I'll get the measurements out tomorrow when I get back home and I'll post some picks of both the Cat and GMC valves for comparison.

The valves are 1/2 inch shorter over the stock GMC valves as you can see in the pics. It's possible there may be longer versions, if not I'll just go with some Custom Manley stainless steel valves