LA 360 piston ID

[RustyRatRod]

Factory crank according to casting number, 645 stock rod, 4.030” bore.

Are you 100% sure it's not .040? Maybe you're measuring unworn cylinder at the top or the carbon buildup?

 

[RustyRatRod]

Double check,tomorrow

See if you can catch a ridge with your fingernail, OR if you can scrape some carbon off the very top about 3/16 with your pocketknife. Also.....what are you using to measure the bore?

 

[RustyRatRod]

Telescopic gauge and micrometer

OK good. Then you're not measuring the very top unworn part of the cylinder then, right?