my friend has a 06 cammed 5.3, with stock 706 heads... (918's springs)

what will his compression be with port/polish, and .030milled and stock valves?? some body told him his compression now is 9:5 and with the above work done on the heads it should go to 10:1

is this true?? thanks for the help...

 

yea thats pretty close, might be a little higher but not positive. I'm pretty sure with .045 milled you get about 10.4-10.5

edit* this is stock other than milling, port and polish will change things

 

from what a few engine shop around here say for every 5ths. you go up 1 number so if it is 9.5 stock you shave it 5ths it will go up to 9.6.
don't quote me i am going by what i was told when i builded my new engine

 

I am going to assume you meant 5 thousandths. as in for ever .005 you get up one tenth. for .040 would gain .8 points of compression. I have heard this also

 

I use .007" as a mill/cc ratio factor. The 5.3l is indeed factory rated at 9.5:1 c/r. So milling .030 would reduce the chamber volume by about 4.3cc. Each cc starting at around 9.5:1 is worth about .12 of a point of compression. I see that milling .030" would net you right at 10.01:1 c/r. Your mileage may vary.

Good luck,

Richard