I have MP Pistons I would like to use PN 3690834 they are 0.030 over raised dome pistons and according to MP 11.5:1 compression, probably calculated with 88cc heads,

Is it ok to mill off the top of the dome to lower the compression to 10.5-10.75:1 and can you figure out how much would be needed to mill off?

Before milling the dome, look inside the piston to see if there is a depression that matches the shape of the dome. If there is, it would be wise to measure the depth of the depression and compare it to the dome extension to see what the actual thickness is.

The inside bottom of the piston is not depressed according to dome just flat bottom.

If anyone have these old DC or MP catalogs with these pistons, the numbers specs would be very much apreciated.
Thnks

I have some TRW L2295Fs.

In a '70 stock block they sit in the hole .050.

I think using an unmilled open chamber head @ 90 cc. gives a compression ratio of 10.3:1. To get the 11.5 you would need a cylinder head of around 78cc and an .020 steel shim in a stock block. 440 deck heights are all over the place so your milage may vary! BTW the cc of the dome is 12.1cc

Are they the old TRW forgings? If so no need to mill them (unless the small dome is a problem) w/88cc cyl hd they should be about 10.7 or less with undecked block.IIRC they called for the piston to be below the deck -.020 and depending on cc of the heads were anywhere from 10.7 t0 13.5. Need to check the deck height.