Whats the diffrence in the cranks , both are 4" stroke right . How bout length , journal size , ect. ect. 

-beerjet-

IS  this the info you are looking  for?

 454 = 4.250" x 4.00"
502  = 4.466"  x 4.00"

ALL Chevy big blocks used...Mains-2.7488"-2.7495"---Rods-2.20"

The Gen.V and Gen.VI crankshafts for the 454 and 502 motors share a 4" stroke and a one -piece rear main oil seal, however, they are not balanced the same. The steel Gen.V 454 crank is PN-14096983, while the steel 502 crank is PN-10183723. Both are externally balanced. The Mark IV 454 and 502 "1053" steel cranks, for use with two-piece rear main seals, is PN-3963523. A forged "5140" Mark IV 454/502 4" stroke crank is found under PN-3963524. If you are looking for a 3.76" stroke forged crank to use in a '91 or later Gen.V or VI block with a one-piece rear main seal, you can use PN-10114186. This crank came in Gen.V/VI 427 tall deck truck blocks.

Keep in mind that the Gen.V/VI big block production motors made from '91 thru the present have non-adjustable valvetrains. If you want to convert them to adjustable valvetrains use the guideplates, pushrods, rocker arms, rocker arm studs, balls and nuts from a Mark IV setup. The Gen.V/VI valvetrains use a rocker arm bolt (instead of a stud) that has a 3/8" diameter thread going into the head. You will have to drill and tap the Gen.V/VI head to accept the Mark IV rocker arm stud. The Mark IV uses a 7/16" thread stud. The Gen.V/VI production rocker arm is different from the Mark IV and is not interchangeable with Mark IV rocker arms.

I was lookin to see if a 454 steel crank works in a 502 block .

Basically everything has to match Gen wise correct. Gen IV cranks with Gen IV block ect ect .

-beerjet-

Yep...MkIV blocks use a 2 piece rear main seal whereas the Gen V and VI use a 1 piece rear main seal.

Omar , Several companies make a rear main seal adaptor kit to make this happen,  Tom

I know of a guy that has several blocks. I'll be givin him a call tommorrow , see what I can scare up .

-beerjet-