Forged to Cast piston in a Blaster

[J-Madd]

I think I know the answer to this, but a friend of mine has a Blaster that had a forged wiseco 67.00 mm piston that had a ring snag, and is re chamfering the ports and bought a Namura 66.92 cast piston. Can he just hone and drop this in?

[Coupelx]

Most likely not especially seeing the size difference.. You need a fairly tight clearance for a cast piston.

[BANSHEE HP]

They the same size pistons but measuring the bore and finding the clearance is the right way. .003-.004 for a cast blaster piston

[J-Madd]

I always thought the cast pistons swell more? I told him to measure the piston to bore clearance.

[Coupelx]

Forged grow more.

[lms1977]

Cast is is usually .001 less clearance.

[J-Madd]

Good to know. I could've googled that shit and not seemed like a dumbass, lol. I knew they had different clearances.

[J-Madd]

Guess that makes sense. The molecules are closer on the forged. I was thinking the cast had more room to move because of the space between the molecules, but they could expand into that space, and the forged cannot. I didn't google that shit, was just thinkin backwards.

[Zillaguy]

I always run forged pistons a little loose... That way when they are at operating temp they are within spec.. Other wise they will be too tight at op. temp. and can lead to heat seizure.

[Coupelx]

I run shit as per manufacturer specs.