Piston ID?

[Tom Jennings <tomj@xxxxxxx>]

My .030" over 258 has pistons marked "L3103F". Google turns up
nothing. Can anyone ID it?

The head appears to be stock; stock size valves, no evidence of
porting.

The flat of the pistons come up to approx. .036" of the deck, and
the dish on the pistons are 3/16". A Felpro gasket I have, the
thinnest point is .050". The piston dish covers most of the
piston, so there's not a lot of squish space, but it should be
.087". This doesn't sound like high-compression to me (what the
engine is alleged to be). I know there's a dynamic aspect to
compression but I don't know anything about it, and I have no idea
what cam is in there. It's got double valve springs, the inner are
flat wire.

I suppose I could get a degree wheel and measure the cam.

Man, I'm itching to build a motor and do this crap right.