Piston Woes
 

Finally got back to my 930 rebuild. Picked up the hard parts from the machine shop and everything looks great except for a couple of pistons that look to have fallen victim to over boost. My machinist doesn't seem to think its a huge deal to continue to run these. My anal retentive - pessimistic side has me wringing my hands over what to do. These are stock 3.3L pistons. Two out of the 6 have similar damage on the surface and edge. The smooth finish has been burned away leaving a porous texture exposed.
http://forums.pelicanparts.com/uploa...1306043007.jpg
http://forums.pelicanparts.com/uploa...1306043025.jpg

JMHO. but those should be consider "ornaments". Detonation has eaten away the circumference as well as the top ring land and that makes them effectively, junk.

Time for new ones as well as a thorough search to find the cause and keep it from recurring.

+2 that ring land area looks toasted......

Time to find a new machinist. The pistons are junk and if the machine shop OK`ed them what else? It`s up to the one doing the final assembly to double check all tolerances , and if the engine goes south thats exactly what your machinist will tell you.
Not just your machinist any machinist.

Junk
 

I have not seen many that look worse than that still intact, be sure you check your fueling/boost levels or this will happen again quickly

Mike Bruns JBRacing.com

Thanks for the feedback.

I'm looking at a set of used P&Cs. Anything in particular to look out for? Aside from the usual visual and measurement checks should either be tested beyond that?

Thanks,

Newbie question here.
Is it alright to etch the number three so deeply into the piston. Wont it cause a "hot spot"?
Thanks

As long as the used pistons are well within spec: ring lands, skirts, pin bores, and do not show ANY sign of detonation, they will work. Naturally, the cylinder bores should be perfect.

I saw an Aluminum connecting rod big-end cap from an AJ Foyt Indy engine that had cracked due to a stress riser. The cause? A stamped number 3 right at the thinnest, bottom middle, part of the cap.