Small Cracks in The Bottom Of the Pistons

ok. this is what I was told by an old tafc racer a long time ago. during the firing stroke, the piston is pushed down by the explosion. during the exhaust stroke, the piston is thrown up, stopped dead, an then pulled down by the crank. that pulling down wants to pull the top of the piston off, creating the cracks. it sounds reasonable to me, so I believe it to be true.

 

My Ross pistons have 147 passes at 26-32# boost and 8-8400 shift point, I also use a two step on the starting line at 3400ish RPM. No cracks, pistons look great. 540 12° BBC going 3.80-3.70 @ 2000#

 

Mike , we had similar issues with the boat with CP pistons. At that time we were dealing with a guy called Mike Lazano I think. We were using ther 545 forging and swapped to there 544 forging which to muy understanding was for a smaller bore piston making it thicker in that area. We also put a generous radius around the inner skirt pin boss area. so far no issues.