502 Mag MPI o.s. pistons
 

What pistons have you been using when boring the 502 for example .030?
I'm facing a rebuild or possibly a new long block but I'm interested in cost of the rebuild to start with.
From JE I've heard the original style pistons are no longer available, they recommend a flat top instead (part # not known at this moment).

The engine is one of two in the boat so I don't want to alter the performance figures to much.

I think the stock pistons are just a forged TRW. If I remember right, they use metric rings. The numbers are stamped lightly on the piston.

From what our guru Dennis Moore wrote in his book they're JE, not TRW. Also that's what the reply I got from JE says.

TRW's, to my knowledge, are used in the 454 HO's

I went with Speed Pro/TRW in my .030 over 454 MAG MPI back in September. They aren't the lightest piston on the market, but they are know for being really strong.

I used a set of Ross pistons yrs ago. Had a bit higher dome on them. Bored the motor to 4.520"..... PN 22-201.
That was back in '96. Not sure they are still available??

Hope this helps.
Dick

Alex,
I am pretty sure that Wiseco still has the original style pistons, or at least they did a couple of years ago. I will try to remember and check on Tuesday.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I bought J&E last year for mine. They were high( $600?) I can post the part # later if you like.

I was going to rebuild one of my 502"s. Deceided to buy a new engine but GM does have .30 pistins available. Stock compression. I think 8.75.

Thanks BillK,
However I just browsed thru Wiseco's catalogue and I couldn't find any suitable (8.75:1 cr) 4.500" pistons there.
Do you have another source?

If not too much trouble please do dig up the part #.
Were they flat tops or did they have the small dome like the factory installed pieces?

In the reply I got from JE they had a flat top replacement for the old domed piston. The weight difference had to be counted for so re-balancing is a must.

Starting to sound like a consederably large amount of work and $ with regards to the block not beeing that reliable due to extensive salt water use ...