Can anyone identify the bore size on a factory 1970 L78 (396-375HP) piston, GM PN 3969974. I believe it is standard but my local GM dealer can't provide any information. Appreciate the help.

Stock, 396 bore should be 4.094".

And don't forget the piston's clearance is taken off the piston so it may be a schosh undersized by the recommended running clearance.

pdq67

Thanks PDQ67. Really appreciate the info!

396 (375 hp) comes from the factory with a 4.094 bore with forged pistons that are 4.0865 O.D. measured at the skirt........there is some plus or minus on the skirt but this is what they are to measure..........