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For the last couple of weeks I've been looking for a good short block to start building an engine with. I found a very good short block out of a 92 Chevy pickup, the bottom end was completely rebuilt, bored .030 over hypereutectic pistons. It doesn't have a cam, lifters or timing set. It is really a good buy. The guy that has it for sale was building it up for his pickup and ended up going with a LT-1 out of a wrecked Firebird.
Now the problems with using this block, it has a single piece rear seal. I know that this is a problem. What do I have to do in order to use this with my car?
Everything should bolt right up. The only difference is the location of the dipstick which is on the passenger side, and the oil pan. If you got the heads then you would need center bolt valve covers. GM improved the sealing on this block. I believe that this is the only major difference.
I think there's a difference in the flywheel flange bolt pattern. Engines built before 1986 had a 3.58" diameter bolt circle and engines built since then had a 3.00" diameter bolt circle. You might check this out to be sure. If it's an issue, GM makes various flywheels/flex-plates. There's probably one that you could use to make the swap.
I was curious if a earlier (72) pan would work on one of these post 87 blocks? I also know that there isn't a facility for a mechanical fuel pump, but that isn't a real problem since I am going to an electric anyway. Flexiplate should't be a problem either.
I have a later style block in my 76. I ended up using a flywheel from an 86 IROC. The bold circle is different. But, also, the newer 350's are externally balanced. This means that GM corrects the balance of the engine, partially, in the flywheel (or flexplate). I was also unable to use my stock clutch, which had an 11" bolt patter - as opposed to the newer 10.5". Everything is working well, though. The parts are available in aftermarket and from GM.
You need the oil pan, flywheel, and front balancer that belongs with the newer motor.
I highly suggest you getting the original style hydraulic roller lifters and rev kit and upgrading to a nice aftermarket roller cam and high quality timing chain.