lycoming dome pistons

[Anonymous]

I picked up a set of domed pistons for a 540, anyone know how to tell which ones they are? I was told they were the high compression but that could be 9to 1 - 10.5 to 1. the only thing i see in the piston is M5

 

[marshmaster pat]

I cut and pasted this reply that was to the same question as yours, from a Lycoming discussion group.

"Most pistons manufactured by Lycoming are stamped with a P/N between
the pin holes on the underside of the piston. They are stamped very
lightly and if anyone has blasted the pistons to clean them, the stamp
will be likely very hard to see if at all. The rest of the
manufacturers normally stamp the piston on the head or top. Again if
they have been blasted it can be very difficult to see the P/N."

Hope it helps