I have 16k miles on Probe pistons. I averaged two NASA events per year since 2010. Also dynoed 327WHP and 357ft-lb on 15psi. So over all, and given the cost, I am pleased with the probe pistons. HOWEVER, do note the following:
1- The machining on the valve reliefs creats extra thin areas on the crown, and to avoid the possibility of melting these razer sharp edges I had to grind down by hand these edges. Here is a picture of what I did:
http://s622.photobucket.com/user/bdg8racer/media/IMG_2265.jpg.html?sort=3&o=27
I can send more if needed, but that should give you the idea.
2- as with most forged pistons, they will slap due to extra clearance needed to allow for expansion. Also, some forged pistons have an offset pin to reduce the noise of piston slap, I believe the probs are not offset. From my experience they are actually not very noisy on startup, but as the block worms, thus expanding the bore a bit, the slapping is more noticeable. Then as the oil reaches full operating temperature of about 185F, then the piston expansion catches up and slap is hardly audible. When I pull in to the pit area after a track session there is no piston slap. So these are more race than street pistons in my opinion.
3- I would consider a skert coating to tighten up the clearance and thus reduce slap.
4- the skerts are shorter than stock, good for reving but only makes slap more likely.
So determine your needs before you commit. For me, I wanted an engine that has lots of race capability and less street, so noise before worm up is not an issue to me, but for others it might. It all depends on what you want to do with the engine.
