434 crate motor
421/427/434/454 allright a 421 is a 4.155 bore with a 3.875 this is usually done on a stock block .A 427 is a 4.125 bore with a 4.0 stroke a 434 is the same accept it has a .030 larger bore and a 454 is done a two ways a 4.250 bore with a 4 crank or a 4.185 bore with a 4.125 crank.This is my opinion on these combos.If your going to build a 427 or 434 you build it with a 9.325 deck height block which is +300 tall deck.Also going with this type of block you run a raised cam journal +.391 this in turn picks the cam up away from the connecting rods so there is no clearancing done to the rods also .Another trick I do is run a 55mm cam hole which in turn you can make a faster camshaft ramp because its larger and not affect the reliability of it.So 427 or 434 as far as I'm concerned its the same motor just make sure it has these features.the 9.325 deck allows you to use a 6.200 long rod which makes your rod ratio much nicer.The 454's i would steer clear of one has to much bore for the casting meaning the bore center of a smallblock chevy is always the same so the material between the cylinders is not enough on the 4.250 deal not to mention the gasket sealing surface especially with two exvalves right there.the 4.185/4.125 is a better way but thats alot of stroke which runs into cylinder wall wear.I think the 427/434 tall deck is the way to go.and i would be glad to build it either way.Thanks Tom
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