Although Chevy and GMC shared chassis and bodies, GMC's used a different
family of engines through the 50's and most of the 60's. Generally larger
physically, with thicker castings, bigger bearing surfaces in some areas,
always full pressure crank oiling systems. They were designed as truck
engines, never offered in any GM car, and were considered by some to be
superior to the "Stovebolt". Actually all GMC inlines have solid lifters,
there is no oiling provision for hydraulic lifters. GMC's typically had
stronger internals, like higher volume oil pumps and alloy timing gear sets,
rather than the fiber gears on 235's. The "Jimmys" were made in
displacements of 228, 248, 270 and 302 cubic inches and share many internal
parts, were widely used in military vehicles, and were also very popular for
racing conversions, due to their prodigious torque and rugged bottom end
design. When raced in sprint cars, they became known as "the farmer's Offy".
These engines were never produced in the volume of 235's, so parts can be
more difficult to locate, and sometimes more costly. Some 235 parts like
water pumps and distributors are the same, although they may carry different
part numbers. GMC radiators are different from Chevy, but bell housings and
drivetrains were identical.
If your 55 motor (probably a 248 - first 3 digits of the engine number are
the displacement - look on the block to rear of distributor) is running
well, there's no reason to replace it with a 235. It would lower the value
of the truck and require modifying the front crossmember for the shorter
235.
Jack / Winter Park FL
----- Original Message -----
From: Keith Breuer <kbreuer@sgi.net>
To: <oletrucks@autox.team.net>
Sent: Wednesday, November 03, 1999 10:40 PM
Subject: Re: [oletrucks] 55 GMC 150 motor?
>
> > Another dumb question: I just got my "new" GMC 55-1
> > running, but was surprised to discover it is not a 235
> > motor. I already have had to special order a valve
> > cover gasket, and am wondering if a 235 would be
> > better. What motor should be in this truck? How does
> > it compare to the 235?
>
> The only dumb question is the one not asked.... But you might get
> some dumb answers!
>
> The 55-1 came standard with the GMC 248. It offered a little more
> horsepower than the Chevy 235 and hydraulic lifters. I believe the
> over all length of the Jimmy engine is longer than that of the Chevy
> also.
>
> Keith Breuer
> kbreuer@sgi.net
>
> ---------------------------------
> My 1947 3/4 ton Chevy Web Site
>
> http://www3.cybercities.com/k/kbreuer/
> ---------------------------------
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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