About 8 years ago I had my 455 rebuilt ( has never been fired ) with .040 Federal Mogul hypereutectic's. It's basically a stock rebuild other than a Comp 268H cam. The guy that built it was leary of the .0015 clearance that is specified, and set it at about .00225 (about what Keith Black called for with that bore size). At that time he had used the Keith Black hypereutectic's in several performance engines and claimed to have great success with them. He said the only problem with the very first ones he used was pulling the tops off because of too tight of ring end gap. I know the GS Club mentions .0015 to .002 and to be sure the cylinders are round, and TA performance told me .0015 and absolutely no more than .002. This is a numbers matching engine for my 72 GS 455 conv., and I don't want to take a chance on screwing it up. So my question is do you think that little bit extra clearance could cause a problem ? I would appreciate any advice. Thanks, Tim
Excessive clearance is the worst thing for those pistons, the KB's tend to be a little better quality and that is probably why they can run a little looser. The FM's don't hold up well with the extra clearance. Not to scare you too much, but that is the whole reason why TA doesn't sell them, they are unforgiving. So many builders are reluctant to stick to the recommended clearance, then the skirts break when they rock in the bores and takes out half the engine with the debris. Dave
Dave, I appreciate the reply. Do you think the extra .00075 (3/4 thousanths) clearance from what is specified would be considered excessive ? If so I have a couple options I guess. The easiest is to find another 72 engine and build it, saving the original. My engine is all painted and detailed, and disassembling it will really screw up the paint. And it would look like crap just touching up where the paint flakes off. Also if the specified clearance is "built into" the pistons, if I opted to go with the Speed Pro forged or just standard cast .040 overs, they would also be a little sloppy in this block. Thanks, Tim
