Cast vs. Forged

[fatones]

I was reading about pros and cons of forged pistons, and it said that to run a forged piston you must allow for the expansion of the piston as the engine warms up to operating temperature. So this means a larger piston to cylinder clearance that initially will wear on the cylinder more since it will take a little while for operating tolerences to expand to normal. Does anybody know the life expectancy of a forged piston engine versus a cast piston engine? I'm sure it will be less, but I've never heard exactly what to expect. Also anyone ever see hypereutic pistons for a Z? Thanks Fatones

[Phred]

Hi Tim,

FWIW, I built a forged piston engine for street use, a few autox, and general driving. I started it out with .005 pist./wall clr. After 54K miles I took it apart mostly cause I just wanted to see how it was doing, and for a rebuild. Every thing was fine, so I honed it and put in a new set of rings. It then had about .0055 clr. I sold it so I don't know how long it lived after that. Iv'e heard some people say forged piston engines make a little more mechanical clatter till their warm, but I couldn't say that. Consider stock cast pistons have about .0015/.0025 clr depending on where you measure them, against .005/.0055 for a forged one. .003 difference, not much. I have never used any of the hyperutectic

pistons.

Phred