ok i came across a 402 block and heads for 160 dollars casting numbers block 3999290 date a-28-72 heads 6272292
or should i wait and try to find a 427 whats the advantage of the 427 or 402??? please help

 

402 - 4.125" bore.

427 - 4.250" bore.

Some of the smaller bore castings can be bored out to the 4.250" bore. Instant 427.

Other than an extra 25 cubes, the larger bore unshrouds the valves a little bit so you can use larger valves more effectively. The heads are open chamber, meaning less valve shrouding, but you need good dome pistons to keep compression up. I don't have adequate data with me to say whether those heads are the "good flowing" open chamber oval ports people are looking for, but it wouldn't surprise me.

Supposedly mine are the "good flowing" closed chamber heads with 260cc intake ports. Perhaps one of the real BBC gurus that freqent these parts can respond with more details.

 

If you want a 427, I wouldn't bother waiting around for one, they are far too rare. I suggest you get your hands on a Chevy 454 because they have EXACTLY the same bore as a 427, you just need to find a 3.75" stroke crankshaft to put in place of the 454's 4" stroke crankshaft. This is the easiest way to get your hands on a 427.

You may even be able to use that 402 crankshaft in the 454 block to make the 427, since i think the 402 and 427 have the same stroke!!

Sounds like a cool swap, good luck with it

 

All correct, except 396/402/427 stroke = 3.76".

If the 402 block has the thick cylinder walls, you can make it a 454 with the 4.250" bore and 4" stroke.

If you have a 454, don't mess it up with a shorter stroke. It just doesn't make sense to give up available displacement.