dvalen11

So I want to buy a new 502 block for a rotating assembly I have from an hp500 motor. The pistons are JE and require an metic ring pack from JE which only list a bore size of 4.468. All New GM 502 blocks 540 casting I've seen for sale state there bore is 4.470. That would mean I would have .002 extra clearance in the bore. JE also list ring pack for an 4.470 bore but are fractional rings which will not fit my pistons. What gives ? Does the merc motors from GM come with a smaller bore? Anybody else run into this?

dvalen11

Did some more digging and a merc manual states the bore diameters tolerance are 4.4655-4.4662and a piston clearance of roughly .005 to .006 Anybody have an idea where to find a std bore block with this bore? Anybody?

dvalen11

It seems like Im not getting much help on bore size. So I have a differnt question on piston to cylinder wall clearance maybe someone can help me out with.. Measured the pistons I plan on using JE700 no part number on them from a HP 500 502. Get 4.462 at .500 up from bottom of skirt. Is .008 too much piston to cylinder wall clearance based on the 4.470 bore from a 502. This it the part number on the block I want to use GM19170540 502 BARE BLOCK

dvalen11

This is going to be naturally aspirated forgot to mention