I CC'd my merlin cast heads last night and the aveage cc was 125 ( varied from 123 to 127) With my Manley pistons which are 49 CC's and a .005 deck my compression drops to the low 12's/. I'd like it back up to the high 12's. Should I look @ milling the heads to reduce the chamber CC's? 2nd question is how close do the CC's need to match btwn chambers. I don't want to grind out any more than neccessary so fare I just smoothed and polished them.

460C.I. BBC 4 bolt mains ARP fasteners throughout
Steel crank Chevy steel "dot" rods 7/16" bolts
Marlin cast iron heads with rectangular ports 320cc 2.300 intake & 1.880 exhaust Valves
(before porting )

Erson cast alum roller rockers 1.7:1 ratio, 3/8" push rods, Moroso stud girdle

The pistons are Manley .030 454 with stock length rods ( 6.135 ) and 4.000 stroke and the compression is 13:1 w/ 114 cc cylinder heads. The dome volume is 49cc.

Thanks for the help.

I had my 049's flat milled awhile back. I had 0.040" taken off the deck and I think (??) 0.020" off the intake side.

It took my chambers from about 122cc to 113-114 cc.

TWC,

If you want the compression the same you need the cylinders pretty close. 4cc's on a 12.0 rat is pretty substantial. Like a half a point.
Flat milling is right at .005-.006/cc, it varies a little with chamber shape.
So to go from say 12.3 to 13.0 you would need to cut to 118cc from 123 which is only .025-.030" but you want to check at about .020 to be sure as the .005/cc rule is not written in stone :D
You know,,,,cut once measure twice,, graemlins/clonk.gif
When I cut heads I cut them the same on the intake side as the deck side.