Originally Posted by blueprinted
Believe it or not it is quite common to break or crack trw forged pistons. Normally its the skirts that crack or break. Main reason is too much piston to bore clearance and usually in older engines with a lot of wear.
That isn't a really piston problem--it is an assembly/machine problem. Clearances need to be observed and the recommended specs of about .0015" are a bit too much, IMO. I prefer to be at or near .0008" to .0010". This is too tight for nitrous use, though. I've found that .0012" is about perfect for most uses with .0015" to .0016" the maximum for a high output nitrous engine, but then I'd recommend a different piston than a TRW/Speed Pro/Sealed Power part.