My brother has a 425 that he doesn't know what to do with. He acquired it in a trade and has no plans for it. I am waiting for him to get me the block ID.

I was thinking of taking it off his hands but need to know what all the pitfalls of running this motor entails.

If I put it in a vehicle it will probably be in my 70 Cutlass S after the 350 goes **** up.

So, are parts hard to find, is swapping a from a 350 to a 425 more difficult than a 455? Am I sacrificing any performance going with a 425 vs. a 455?

I was going to get a 455, but I'm pretty sure I can get this motor. The plan is to rebuild the motor over time and have it ready after I decide to part with the SBO.

d1

 

Both the 425 and 455 are great engines to build up. More people build 455's because they built them for more years then 425's.

You won't have any problems swapping it in. If I was you I would get even if you decided to go with a 455. You can't have too many extra engines.

 

The 425 is a great engine and the same externally. It should be a steel crank. Be careful on what the cam bank angle is, the early engines may require a different cam grind. I know you can add a 455 rotating assembly to a 425 block, someone did it to mine. I would rather have the 425 for it's shorter stroke, but what do I know I prefer a 327 Chevy to a 350.

 

All 425 motors used a forged crank. The only issue in swapping is that the crank flange bolt pattern is different on the 64-67 motors, so you need a flywheel/flexplate that matches. The 350 flywheel won't work.