Inliners International Forums General Discussion Engines Need help to ID a GMC motor

I have a club member with a motor out of a '51 GMC. The numbers
by the distributor are C 2488022 9. I searched the Casting # pages, but didn't see anything close. I'm trying to get Block and
Head casting numbers now. Grateful for any help.

Texas/Gulf Coast Inliners

It's a 248 Cubic Inch. Probably has a small port open chamber head. Tons of rebuild parts are available. Add a 270 crank and get a 256 inch. Good Luck

On a GMC the first 3 #s on the flat by the distributor are the cubic inches. C 2488022 is a 248. Depending on tour plans a 248 is a strong engine. How many Chevy guys are happy with a 235? Too many people can not be honest with them selves when it comes to engine choice and build. A strong 248 is a good street choice and looks just like a 270/302. Beater

Thanks Beater and Jimmy Six for the help.

Glad to help. Your 248 can be a 270 with a crank swap. Same rods and new pistons. If you need that.

The 228-248 have the same stroke and deck height. The 270-302 have the same stroke and deck height. All use the same rods. The 248- 270 have the same bore. A 248 with a 270 crank and modern custom pistons would be a 270. Bored it could be a 292 or so. A 302 bored with a 248 crank would be about 300. Lots of combos even with stock stuff but when custom rods, and pistons come in it gets interesting. Then there are Ron Golden's Hudson rods with 1.25 lbs saved per cylinder. It's just too much fun.

I have the Califronia Bill Fisher book, he talked about building a short stroke 270 out of a 248 block with a 228 crank and apropriately oversized, aftermarket pistons, IIRC.

The 228 crank is supposed to be lighter, the 248 block is supposed to be capable of a larger maximum bore (bigger total overbore).

That combination should rev quicker, and survive longer at sustained elevated RPM.

If you want that.

I was looking at building a warmed up 228 for a '50 GMC truck as just a street driver, and some people I got to "talk" to via this forum and others relayed the 228 with a modern build (good compression, mild cam, good intake, decent exhaust and reasonable gearing) should return ~ 25 MPG on the highway, where as the 270s and 302s they had tried returned less than 10 MPG, but I suspect that had something to do with how they were driving them.

The stroke difference is 3/16", which lowers the reciprocating tensile stress by about 2.4%: 270, 302 etc. at 6,000 = 248 etc. at 6,146 (A=X).
The drop in power by destroking from 4" to 3-13/16" is about the same: 2.4% (using Lanchester's formula), net result is slightly less power at mid speeds, about the same at both peaks.
The rod ratio is slightly better for the shorter stroke, but it doesn't do much: 1.75:1 vs. 1.836:1.

Have a running 228 in an '51 GMC,any potential with this engine for a street cruiser. Would have 5 speed and 373 gear

Potential? You have to remember that the original Wayne heads were designed for the 216 Chevy with no oil pressure to the rods. All of these engines have their unique niches and all have potential. The question is only what you want and will your engine do that for a reasonable investment. A built 228 will not make the power that a built 302 will and will likely cost bout the same. But a good running 228 with duel carbs, a split manifold. and a good cam could be a fun street engine. 228s are cheaper and easier to find than 302s. A 228 might make a good supercharged or turbo project. That may make up for some inches.

Great look, strong parts, full-flow oil system.
The only things wrong with it are size and money.
A blower cures one of those very well, but makes the other worse!