I am helping a friend upgrade the engine in his 48 Chevy 4dr, I believe it is the stock 216 motor. What I need to know is : Will a 235 motor bolt up to the 48 trans ? What years are the best to look for -- insert bearings vs babbit ? Would it matter Auto trans vs manual - cam ? What about a 71 250 engine - what would it take to bolt that to the 48 trans? Thanks for the help
the 235 will bolt to the 48 bellhousing and flywheel. 12v flywheels (1955-newer) have different teeth than 6v flywheels, the starter has to match the flywheel, and you can't swap parts inside the starter. The 250 uses the 55-up V8 type bellhousing, you can't bolt the 48 trans to it, but you might be able to adapt it, I haven't tried. Cam really doesn't matter too much manual/auto. The 55-up 235 has a different block with the water pump of a different design, that is longer, so you need an adapter to put the early pump on it, or a shortened later pump, although that might put the fan too low. Also mounts were changed over the years on the 235, some have them on the front, some on the side, and differen blocks may or may not have the mounting bosses you need.
The best 235 for your car would be either a '53 Powerglide engine or any '54. They have the old style water pump and would offer no clearance problems in your '48, but have the desireable characteristics of the later engines (aluminum pistons, insert rod bearings, full pressure oiling). Be aware that there were two camshaft diameters, '37-'53, and '54-'62. The later cams are easier to find when looking for something hotter than stock, but you can always have yours reground. The 1954 standard shift engine is the only one of the large cam engines that came from the factory with a forged steel camshaft, making it a good candidate for a regrind.
Don't get hung up on the water pump length being an issue. With every one I've done the later pumps only had longer shafts, not the casting itself. It's simple to just use a press to push the fan mounting flange deeper on the shaft to equal the length of the old pumps. Then just cut the excess shaft off. I've done this a couple of times and never had any pump problems.
My '46 Chevy got a swap to a '61 235 back in the day (late 60's or very early 70's I believe) and everything seemed to work out fine on that one. It's got a 12V starter and ignition so I'm going to rewire the rest of the car to match. I think the 250 would be a ****load more work. Post up a picture of the car, I like the 42-48 Chevs.
the pump shaft sits lower on the engine on the newer style engines, so the fan will move down when you swap in the newer engine in a 54 or older car. This may not be a problem, but it is something to consider. http://www.chevrolet.com.au/articles/engine_swap.htm has some swap info
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