Can somebody tell me what the physical difference is between forged and standard pistons. How can I tell the two apart ? Are there any markings. Bit of a stupid question but Im clueless

 

forged are shiney and should polish up even if dirty, they are stronger than standard, standards are just alloy and wont polish up at all, hope this helps, phil.

 

All pistons will polish up, however, forged are easier to polish due to forging process giving them a finer surface finish than the rough, machined finish of a standard piston. Forged pistons have increased hardness and tensility making them able to sustain higher loads than machined pistons. Happy days ;-)

 

If it's a Subaru piston, turn it upside down and look inside at the base.

If it is a cast piston then it will have cross hatch markings clearly visible.

If it is a forged piston it will be dead smooth with no markings.

Phil

 

More good advice Phil. I'm about to get some pistons which I think may be forged out of a block tonight, to compare with my cast WRX ones.

 

Subaru Forged pistons will have:HF,HF1,HF2 etc depending on year/version.




Standard cast piston on the left, Forged HF Version 4 on the right.

Mick

 

Well mine turned out to be cast, although the block did have oil sprays.