hyperion

iTrader: (1)

Hey all,

For years my car has suffered from some smoking under deceleration. In an effort to fix this I was replacing the valve stem seals when I noticed that the #7 cylinder was not holding pressure. I pulled the motor and found this:



This is a stock shortblock with AFR heads, around 10:1 SCR. Never revs past 6800. My tuner set up the car for reliability as I run at the track often. What I'm wondering is what the most likely cause is for cracking a piston like this. I'm taking delivery of a Katech 427 next month and I want to make sure this doesn't happen again.

Thanks in advance to any helpful replies!

-ch

conan

iTrader: (5)

That looks melted to me. Do you have a power adder? My have gone lean on a pass or 2.

DaveX

That is somewhat common, and almost always #7. Don't know why though. One thing I have read that makes some sense is the possibility that the intake manifold flows slightly more air to #7, which would make this cylinder run leaner than the rest.

hyperion

iTrader: (1)

Thanks for the replies! No power adders, and runs on CA 91 octane pump fuel. But it's somewhat comforting (I guess) that #7 is the common failure.

Is this type of failure usually due to heat or detonation?

-ch

conan

iTrader: (5)

Like dave x said, it sorta common on the #7. I have read too that the the # 7 is the problem hole with running lean due to the intake design. If your 427 has forged pistons in it, you that should fix the problem.