PISTONS

[jay1213]

NEW CAM, MANIFOLD AND CARB TURNED INTO A COMPLETE TEAR DOWN AND REBUILD. MY QUESTION IS WHY ARE MY PISTONS STAMPED 390? DOES THIS MEAN I CAN DROP IN A 390 CRANK WITH OUT MY PISTONS HITTING THE CRANK??????????

[court1100f]

yes but you'd also need the 390s Rods to do that conversion the 360/390 both share the same bore 4.05" it the stroke of the crank that determines your final displacment I.E. 3.52'" =360Cid and 3.78" =390Cid and 3.98" =410Cid all three of these displacements are derived from the same block and all three share the same bore diameter the 3.98" Crank came in the 410/428 engines just for you to play with heres a formula for calculating end displacement based on bore and strok and number of cylinders the formula is BorexBorexstrokex.7854x number of cylinders so for example to get your 360s displacement the formula would look like this 4.05 x4.05 x 3.52 x .7854 x 8=360.71 so actually it's a 361 or atleast almost anyway

[jay1213]

i WAS UNDER THE ASSUMPTION THAT THE CONNECTING RODS ARE THE SAME LENGTH, THAT THE PISTONS ARE DIFFERENT 352 AND 360 USE A FULL SKIRT WERE AS 390 DONT???????

[court1100f]

nope and it's more complicated than that to my knowledge from what I've read theres skirted and non skirted 360 pistons the rods are different and you need the right ones to go with the 390 rotating assembly

[DuckRyder]

360's use the "thin" & "long" rod, you need 390 rods.

[sideoilerfe]

i WAS UNDER THE ASSUMPTION THAT THE CONNECTING RODS ARE THE SAME LENGTH, THAT THE PISTONS ARE DIFFERENT 352 AND 360 USE A FULL SKIRT WERE AS 390 DONT???????

yes 360's used the full skirt where as the 390's do not.

[fomocoguy]

i WAS UNDER THE ASSUMPTION THAT THE CONNECTING RODS ARE THE SAME LENGTH, THAT THE PISTONS ARE DIFFERENT 352 AND 360 USE A FULL SKIRT WERE AS 390 DONT???????

yes 360's used the full skirt where as the 390's do not.

This is not always true. I am turning a 1976 360 into a 390 as we speak, and the original 360 pistons do not have a full skirt. I am using a 390 crank and rods paired with the 360 pistons. This will bring the pistons up to zero deck height and give me the same compression ratio as a 390 car engine.

SOME 360's HAVE A FULL SKIRT; SOME DO NOT. You just have to pull it apart and see. 360 and 390 rods are different lengths.

[sideoilerfe]

Perhaps the later 360's didn't have the full skirts but the earlier ones did.