i have a blower engine that dropped a valve and kissed a piston. question is how long is the life spaned of pistons. mine is JE's 8.4 to 1..... the pistons are about 6 years old.

also how far can a bowtie chev be bored out

IMHO,
If a piston is not damaged then it's fine.
As for boring, some will go 100 over but most are comfortable doing 30 in a boat and 60 in a car. I would go 60 in a boat in a heartbeat and did in my stroker 496 (if I would have went 30 over it would have only been a 489 ).

.60 over is fine, you can always sleeve if you hurt it more or crack a bore...

it is hard to say if your piston is reuseable without seing it,but if its not beet up it is probibally ok,the gm bowtie blocks can be bored to 4.600.can you post a picture of the piston?

I saw the piston today, just made small mark. of coarse it bent a valve in the head. this motor is a 540in with a 420 b&m blower.