[John Milner]

Originally Posted by Formulajones

Must be something new because 25 years ago the L2257 TRW 428 piston was a flat top.

I had to machine a dish in them, which ended up being 16cc. Then zero decked the block, or close to it (.004" in the hole) and with a .038 gasket and a 76cc head I had 9.7:1 compression.

Ran that engine for a couple decades on pump gas.

No, nothing new. Strange that yours were flat tops originally as I've had several sets of the L2257's and each set has had the dish. I have a set of L2257's in my '66 421. They had a 13cc dish in them just like my 2282P's which I run in my '65 421.

I did not have a closeup picture of the L2257 number on my pistons in my 421 but found one on the forum that I attached. The 2282P pistons is a set that I have sitting on my shelf for a future build.