Quote:
Originally Posted by Steve C.
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excerpt:
THE STROKER QUESTION
Another misconception that must be cleared up is what happens concerning the stroke when performing this mod. Cutting down the mains of the 421/428/455 crank has no effect on its original stroke, which remains the same as it was in the crank’s respective original block. When you install a larger stroke crank in a 400 block, you are not building a ‘stroker’ per se. (Although many guys just LOVE saying the word “stroker,) Rather, you are simply building the same engine on 3-inch mains. Let me explain.
A 400 has a standard bore of 4.120 inches. A 455 has a standard bore of 4.150 inches. By using a standard bore 455 piston in a .030-over 400 block, you end up with a standard bore 455 on 3-inch mains.
Similarly, a 421/428/455 share a 4.00 inch stroke. A 428 engine shares the 4.120-inch bore of a 400. You use a standard bore 428 piston when using a 421/428 crank in a 400 block, so you can end up with the proper deck height, just as you do when using the 455 piston on a 455 crank.
I haven’t singled out the 421 engine because most guys use the 1967 or later 14-degree valve angle cylinder head. If you’re going to use a 1966 or earlier set of heads with the 20-degree valve-angle heads, you must have custom pistons built. I can do that for you.
end quote
A 455 has a 4" stroke, as do the 421 and 428?
Did Pontiac ever make a block suitable for a 4.255" stroke, needed for a 455 if designed with a 4" stroke?