stevewix

since you have to buy pistons drop the CR down to 8-8.3:1 IMO this will help you a lot with detonation.

Pro Stock John

iTrader: (34)

I run custom Diamond pistons for 20-25psi boost target. I'm around 8.25:1.

y2khawk

iTrader: (5)

We've got mahle turbo pistons in the white TT car. Picked them up straight from Kurt at W2W. GM MLS gaskets. It runs just fine, 25+ psi, 8.84 @155 with 3400lb race weight.

The pistons are not your problem. Hell, we lost an upper o-ring on an injector earlier in the year. 14:1 the whole way down the track, full boost at alot of advance. Didn't touch the pistons.

I ran my JE's so tight on quench last year I could see the maching marks from the heads in the piston coating when we tore it back apart after thunder. Sub .020 with the aluminum rod stretch we figure.

To break a piston that quick, that bad, something ain't right.

JakeFusion

iTrader: (7)

CP pistons are the best, period.

I know of at least two Supra engines running in excess of 1300rwhp at 40+psi spinning to 9k RPM using CP pistons for an entire season of racing without failure.

Beast96Z

iTrader: (21)

I know all about quench, I was one of the first explaining it here when it was brought up a while ago. I was trying to figure how your pistons had no quench deck, but after looking at the pic again, I can see the "bowl" type dish. I guess it was late when I was looking at it last night and it looked like a standard flat top. I certainly wouldn't want to use those pistons in a N/A application, but they should be fine in a F/I set-up. Whichever pistons you decide on, you may want to lower the compression a bit like others have said.

blu00rdstr

Beast96Z - Sorry, I thought you saw the dish pic.

The motor I built lasted 25K mile at 14psi on Diamond forged until I fixed a BOV flange leak and it jumped to 17psi. So I wanted a complete LS1/6 shortblock to save time and better pistons, and the vendor recommended Mahle forged (the Mahle Turbo Forged only fits a 4.00 x 3.62 (LS2/402)).

The motor I bought lasted 30miles and broke after a part-throttle freeway downshift.

This time I want to make sure I have strong, well designed pistons. I don't understand why quench would not be important on a blown motor, since the purpose of quench is to reduce detonation which is even more important on a supercharged motor. If a quench deck is required to prevent detonation, and higher power motors are prone to detonation, why would forged pistons without a quench deck even exist?

Beast96Z

iTrader: (21)

I wouldn't say that it is not important, but it is not "as" important as compared to a N/A motor. I deffinatlly wouldn't want some huge quench area on anything I had. A higher HP motor is no more prone to detonation that any other motor. Any motor can detonate if things aren't right. As long as the tune is on, higher hp motors should run just like any other. I'm sure the pistons that you have, have some thought behind the design. It would be hard to believe they designed a piston to throw the quench off. It sounds like you were happy with the GM gaskets, so I would use those and talk with a represenative at one of the above mentioned piston companies. They all make F/I pistons, so I doubt it would be to hard to find.

magius231

iTrader: (8)

your sorta missing the point everyones making...your quench didn't cause your problems, a bad tune did. Get it put back together then take it to a reputable tuner (not the same one you did before) and get it tuned properly.

blu00rdstr

Can part-throttle cause detonation? I took it easy planning to have it dynotuned after 250-500miles of break-in. The previous motor had 25K miles, this one lasted 30miles, didn't even make it home.

Also, can detonation cause lost ring lands in only two pistons, while the others are fine? Detonation causes melting, not breakage. It doesn't look to me like detonation, there's 'new moon' marks on the heads (soft aluminum) but the piston edge (forged aluminum) is only speckled.

John_D.

iTrader: (2)

Lean combustion drives up temps and causes melting.

Detonation is like hitting the pistons with a hammer on the way back up...

I popped 3 pistons in mine, and the others looked ok.

Beast96Z

iTrader: (21)

I lost 4 motors in a old TPI IROC because the guy who installed them didn't know how to set timing. In each motor, the ring lands cracked and broke. If the pistons hit the heads, then it would seem that your pistons are extremly far out of the hole. Do the pistons that are broken match up to the "moon" marks on the heads? If so, I'd say contact caused it.

NA$TY-TA

iTrader: (21)

And then if you do both at the same time...................

Nickn20

I find it real funny you are so quick to blame the tuner before you know the whole story, READ this car was never floored or beat on, the car probably never saw more than 3 pounds of boost at part throttle, and yet we have read storys of harlan making full track passes at 14:1 AFR and lots of timing, with nothing broken like this. Yes the tune is critical we all know that, the motor was being broken in, so no WOT or agressive driving was done.

I also agree something mechanical is wrong, mahle seems like a good piston to me, maybe not the best out there but decent, and I dont care what piston you put in a motor, if its not built right and/or tuned right its gonna break, plain and simple. The marks on his heads seem like a good place to start.

magius231

iTrader: (8)

who said you had to drive aggressively to detonate? A car can detonate at idle if things aren't set right. Sorry but I fail to see how he has two sets of defective pistons in a row from different manufacturers...