401 and 351 Parts Compatibility
 

I have a 401M engine that must have had water in the cylinders, which are rusted and have already been bored out to maximum available piston size. So the block appears to be beyond repair. But the heads look like they can be salvaged and the intake manifold is okay. Can these Magnum heads and intake manifold be used on a 351C in a medium duty GMC truck to improve performance? Are there other, major parts that fit both 401 and 351 engines?

JMunn

Re: 401 and 351 Parts Compatibility
 

All the Magnum components will work with the 351C, all the 401 parts will interchange other than the 3 piece timing gear set and bigger bore pistons. Though the cylinder bore is too worn down on your 401 you may want to consider having it sleeved, technology on that is really good these days and pistons are available for the 401.

Re: 401 and 351 Parts Compatibility
 

BigBlock,

Thank you for confirming that the 351 and 401 parts are mostly interchangeable. I still have the 401 and need to get inside to see if the rust goes farther than the cylinder walls above the pistons. If there are no other major problems, sleeves are a possibility. I already have oversized pistons that could be put to use. In the meantime, the 351C in my truck is running, but needs carburetor work, and I am thinking of switching to a Holley 500. If I put on the magnum heads and intake manifold at the same time, the truck should run better, have more power, and could be used while I figure out whether the 401 can be repaired.

We may be relatively close (less than 100 miles). Can you recommend any parts sources in the area?

JRMunn