Ken, I have heard it said they will go to 6000 and live. At least that was the ''theory'' when I put together my number 2 motor earlier this year. Anyways, I think I made 9 passes shifting at 56/700 and crossing the line at about 6000. On the tenth pass I ripped the pin outa number 3. Needless to say, that pass ended the career of that engine.......and block.........and pan......and, and, and, well you get the picture. Myself, I won't ever do that again. If I plan on going over 5000 I am gonna have a good piston in there. And I have the third of the piston left as a reminder to myself.............. Later...............
The stock stage 1 with auto was set up to shift at 5,500 rpm when left in drive so I would say on a milder build up, that would suggest at least 5,500. I guess the best thing to do if you have doubts is to go forged. Most people, if they have a problem with a type of part, will avoid it in the future even if others have success with it. I have a ZZ1 SBC with hyper pistons that I bought apart and it broke two pistons below the top ring. Some people love the eutectic pistons but after seeing just how brittle they are, I wouldn't run them even though I know these failed due to BAD detonation and they WON"T tolerate that! Ken
I ran stock 70 cast pistons for literally thousands of runs shifting at 5800 to 6000. They are plenty strong....the key is to avoid detonation at all costs. Bruce
Compression ? was at about 9 to 1. No NOS on that motor. Detonation ? I am pretty convinced that was part of the death nell. I think ANY detonation on a cast piston motor will kill them off. The pin boss(whats left of it)looked ok. No burning scars etc. The rod bearings were ok(although beat to death). If you look at the pin boss that is left close(like magnifying glass close) you can see some signs of cracks running through the area. I really believe there was a crack, and I just ripped the pin outa the thing and turned the rod loose in the motor to tear things up as it saw fit. None the less, I won't ever use them again. All my motors will have forged from here on out.
