KB's and ring end gap

[zeke]

There seems to be some info floating around that I question. That KB hyperurtectic pistons expand more than cast. I believe it's less. And that the ring end gap needs to be different. This I think is true. What is the gap and why? TIA

[Shad Laws]

Hello-

There seems to be some info floating around that I question. That KB hyperurtectic pistons expand more than cast. I believe it's less.

Yes and no.

Of the three major (i.e. nearly exclusive) modern aluminum piston alloys, 390, a hypereutectic casting alloy, expands the least of them, with 4032 as #2 and 2618 as #3. Of course, their strength is in that opposite order... a lovely no-way-to-always-win problem :-).

I suspect that the new cast pistons are also 390... so they expand the same.


And that the ring end gap needs to be different. This I think is true. What is the gap and why? TIA

Ring gap has a lot more to do with the cylinder than the piston. Set them up as you always would.

Take care,

[zeke]

The hypers are the weakest!!? Holy Schmoly, I better get some forged. You say set the ring gap as you always would. What would that be? as I really don't know. I have stock 94s bored to 96. They (KB) are saying twice what your would normally set on the top ring.