I once heard thats a 402 BBC could be bored out to 4.25, making it a 427, is that possible without hitting water, and still having plenty of cylinder wall left?

 

Im no expert but if you have a 400~ block I believe the recommended max is 406-412 with boring, as you WILL "hit water" lol

I think to hit 427 you need a large than 3.75 crank.

On the other hand, they SELL 400CID blocks that you can bore/stroke to 450~ cubic inches. But thats not a run of the mill 400, its a special order only block from a summit magazine.

 

oops

 

You're talking SBC's, OP is talking BBC.

402's have a bore of 4.125" with a 3.76" stroke. According to my book (Chevy Rat Motors by Ed Staffel), if there is no core shift they can be bored over to 4.250". Making a 427 (with the 3.76 crank) or a 454 (with a 4" crank).

 

thank you. thats what I needed to know!

 

An opinion from the other side:

Some 396's, with 4.096" bore, used the same casting as the 427, which was 4.250" bore. So, those blocks can be taken out to 4.250". But, from what I've been told, the 402's, even with a larger 4.125" bore than the 396's, had thinner cylinder walls, and a 0.060" overbore is all you should take them.

Best bet would be to have the cylinder walls measured.

 

I planned to, I've been researching this as best as I can, and it seems very hit or miss, some have done it without incident, others have said you can't, what would be an acceptable wall thickness for a 402?

Thanks-

Eric

 

Quick search:

http://books.google.com/books?id=_i_...age&q=&f=false Says 0.125" at 1" below top of cylinder.

 

Thanks five7, thats what I needed to know.