455 inards comparison

[boatermike]

got a couple 455 olds motors and the differences are obvious. c head has larger valves on the intake side but the same on the exhaust side.The difference is one eigth of an inch.the c heads also have one sixteenth wider intake ports. i didnt look at exhaust ports but obviously c heads would flow more than j heads.
i was surprised that the pistons in these motors were not the same. they are both dished quite deep but one set has much less dish.both sets of pistons are identical in composition and style making me suspect both are factory stock. i was unaware that different compressions were used other than a few heads listed had smaller combustion chamber cc's. now im thinking there was several combinations. the j heads do appear to have larger valve springs than the c heads so i will use them and had lap the valves and seats when i have them apart and also some deburring and chamfering of oil drain backs and port match.
tomorrow i will delve deeper into the olds mysteries and try to determine if i can pick the best parts to use and hopefully put together a happy junk combo.
any advice would be greatly appreciated.

[2slow4u]

70 and older are the pistons u wanna use. 71 olds dropped compression alot and changed the head design for the start of pollution control. the c casting heads are the better and are from the 70 and older gap. hope that helps a little.