637 V8 gas engine
 

This followed me home. :upyes:

Re: 637 V8 gas engine
 

IS THIS CRACKERBOX A '67 OR A'68????:coolphotos::coolphotos::coolphotos:

Re: 637 V8 gas engine
 

1966

Re: 637 V8 gas engine
 

Try this again. 1966 GMC Crackerbox FE model with 637 V8

Re: 637 V8 gas engine
 

Front view.

Re: 637 V8 gas engine
 

WOW! What a find.
Looks to be pretty decent.
How far away did it come from?
Rod Johnson
Issaquah, WA

Re: 637 V8 gas engine
 

A lot of folks have heard about the 702 twin 6, but very few know about the 637 Magnum V8.
The 637 replace the 702 twin 6 in 1966.

I have one in a 67 GMC COE fire ladder truck.
About 15,000 miles on it and it runs great.
Sucks gas like there is no tomorrow.

Parts are hard to find.
Fuel pump quit on me a few years ago and cannot be found anywhere.
Mounts on the front top of the motor and has about a 14 inch reach arm on it.
Ended up mounting an electric fuel pump at the tank.

The pictures and story here.
https://www.stovebolt.com/gallery/ki...on%201967.html

Don

Re: 637 V8 gas engine
 

Great Story on the Fire Truck purchase! Would you mind posting a close up photo of the V8 emblem I see on the front, Thanks.

Re: 637 V8 gas engine
 

Rod, a friend of mine told me about it. It had been on Craigslist awhile back and it never sold. It came up again and I jumped on it. Came out of Colville WA and before that Idaho. Here is a picture of the emblem.:upyes:

Re: 637 V8 gas engine
 

I also picked up a 637 this spring out of California. I got it freed up, but haven't got it running yet. I also got two emblems with the engine from California. Good to have the extra parts.

Re: 637 V8 gas engine
 

Wow Nice pic; I had never seen the factory exhaust on those engines. Do they have a four barrel carb and what does the air cleaner look like?
No rush just curious about the 637.

Re: 637 V8 gas engine
 

Great story on the fire truck Don!!!!

Re: 637 V8 gas engine
 

Hey Funky61 The picture of the engine on the flat bed has home made headers. They came with a cast iron exhaust manifold. I will try to get some pictures for you.

Re: 637 V8 gas engine
 

Only one weak point I know of on these engines is the crankshaft. The crankshaft on the 637 is not flame-hardened(called Tocco hardening or armasteel), instead, it is TUFF-RIDED, a chemical washed on hardener only penetrating .006" into the surface of the shaft. In order to provide undersize bearings, the shaft must be rehardened by either re-TUFFRIDEing the shaft, or chrome plating the journals. On this engine, please use a high-quality SAE30 or SAE40 engine oil (preferably diesel approved). The 305-351-379-401-432-478 gas engines can be resurfaced w/o going to the expense of this process.

Re: 637 V8 gas engine
 

I remember going through some manuals and GMC actually recommended a hardening process called "Tuftriding" after turning the crankshafts . When the crankshaft for my 478M was turned down I requested that it be rehardened, was no problem with my machinist he sent it out for that but told me there was a newer process that superseded Tuftriding which is "Nitriding" and that's what was done on my 478's crankshaft:upyes:

Re: 637 V8 gas engine
 

These engines only came with a 2bbl, the same Bendix/Stromberg WWC carb used on all 401, 432, 478 as well as he 351E and all other Magnum engines. You would think a 4bbl would be more appropriate for an engine of 637 cubic inches. I think a Holley 500 carb would be the first upgrade to do.

Re: 637 V8 gas engine
 

glad to know that there is a more modern method of rehardening these "TUFFRIDED" shafts, Pete. How satisfied were you with the nitride rehardening of your 478M-L/D????

Re: 637 V8 gas engine
 

Lewis, ten years ago I took a class in metallurgy and it mentioned a hardening process called Nitriding, so I can say I'm very happy the crankshaft on my 478 go this treatment topped off with Clevite bearings. I'm real hard on my stuff so the bottom end will hold up fine, my biggest worry now is those hollow stemmed sodium filled exhaust valves, I should have addressed the issue when the heads were built, specially when I was told these engines are notorious for sucking up valves from over revving, that's why GMC put governors on them. So a move in the future will be to replace those exhaust valves with something better:upyes:

Re: 637 V8 gas engine
 

pete, somebody in the old forum/club replaced his valves with ones from a cat diesel engine. I don't remember who it was, but at the time I thought it was a great substitute.

Re: 637 V8 gas engine
 

That is a unique exhaust manifold. I wonder if it came from some sort of a stationary engine application.
Rod J
Issaquah, WA

Re: 637 V8 gas engine
 

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.

Re: 637 V8 gas engine
 

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:ahhhh:

Re: 637 V8 gas engine
 

how much shorter, Pete??

Re: 637 V8 gas engine
 

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

Re: 637 V8 gas engine
 

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

Re: 637 V8 gas engine
 

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.:thumbsup:

Re: 637 V8 gas engine
 

thanks, Pete!:biggringmc::biggringmc::biggringmc::biggring mc:

Re: 637 V8 gas engine
 

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.

Re: 637 V8 gas engine
 

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.

Re: 637 V8 gas engine
 

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:upyes:

Re: 637 V8 gas engine
 

Yes, those were the Steel Tilts, not the Crackerbox aluminum tilt cabs.

Re: 637 V8 gas engine
 

Interesting truck. Never heard of a 637 in a Cracker Box before. I just flashed through the replies real quick and didn't noticed, but what kind of Trans does it have?

Re: 637 V8 gas engine
 

The Crankshaft can't be that weak, lol.

The '71 9500 I used to drive had a 637 V-8 Gas with a 10-Speed Road Ranger behind it. I was the 2nd driver of the truck. The first driver was old school 5-Speed, 2-Speed and never learned to shift the RR properly. He did fine Up-Shifting, but never learned and probably never even wanted to learn how to Downshift a Non-Synchro Trans. I rode with him a few times and could not believe how he would lug the heck out of it, which we all know wreaks havoc on a Crankshaft. I would always joke saying that the Crankshaft is going to end up on the front seat someday.

Anyway, I left the company after about 3 years. Then one day saw the truck when it was about 15 years old, for sale as is by another owner. And guess where the Crankshaft was?

We would haul some heavy loads with it. Probably up to 48 or 50,000 on a 46,000 GVW truck. It's amazing how long that Crank actually lasted.

Re: 637 V8 gas engine
 

It has a 10 speed transmission.

Re: 637 V8 gas engine
 

Just curious, is it actually a 10-Speed Fuller Road Ranger?

Re: 637 V8 gas engine
 

Yes I think it is.

Re: 637 V8 gas engine
 

Looks like it is. Now what is interesting, if the Engine and Trans are both original to the truck, this means that you have only the 2nd Engine-Trans combo that I have ever seen, as well as ever heard of, since I first saw our truck that got delivered in April of '72.

All the 637's out there that I know of are either 5-Speeds, 5-Speed/2-Speed Rear or have 2 Sticks.

Would love to go for a ride in your truck sometime, but we are about 2500 Miles apart, lol.

Re: 637 V8 gas engine
 

BillT
You are welcome anytime to come out here and go for a drive in the crackerbox. I also have a 62 GMC 7000 with the 702V12 you could take for a spin too!!

Re: 637 V8 gas engine
 

I was never around any Crackerbox GMC's but the guy Dad drove for the longest hauling livestock had two L-series Steel cab GMC tilt cabs, one had a Working '5th, from high 3rd you went to low 4th, low 5th, shifted the axle to hi, and 4th, then 5th in high. The other one had a conventional 5+2. Both either had 401 or 478 engines. Later on he bought a Chevy C70 with a Toroflow diesel that had the cab of a GMC B series. Bet that's a pretty rare truck today! It was actually Dad's favorite truck once he disconnected the exhaust stacks from the top rear corner cab mounts, they set up a deafening vibration in the cab, but the truck had fair performance with the BIG V-8 Toro-Flow, 5+2, power steering. At that time his other two trucks were Emeryville's, climbing up and down into and out of them got old, Dad let the younger drivers run them.

But anyhow, Awesome fire truck. Bet you could make good money washing 2nd, 3rd, and 4th floor windows, cleaning gutters, pruning trees, etc. I'm not a fan of ladders!

The Crackerbox was the epitome of a minimalist truck. Minimum cab, short wheelbase, big engine and transmission. I drove a couple TransStar's, a CL9000 Ford, never got into the Astro 95 or White Road Commanders my company had, all their tiltcabs had bunks. Put lots and lots of miles on a pair of RoadBoss 2's and an S2200 Binder.

Re: 637 V8 gas engine
 

Appreciate the invite. Wish we were closer, lol. Nice collection of trucks there. Tell me more about the GMC in the middle. Looks like it has a Heavy Front Axle with the Wide Fenders on it.