SoonerBrad88

iTrader: (15)

I'm taking my motor apart since it ate a valve and installing some new heads, forged pistons and rods. The pistons are Mahle flat top 3.905 with valve reliefs and +4cc volume. Since I'm increasing the cylinder volume and losing compression I'm going to mill the heads some more.

I'm shooting for 11.2 compression. The heads I'm going to run are some worked 243s that have been milled .005 making them ~63.8cc chambers so im going to take them another .025" and run a .040 cometic. Here's what math I came up with:

Combustion chamber with new heads and .040 gasket= 62.7cc
+ new pistons increasing my chamber volume by 4cc I need to take off almost 7cc from the heads combustion chamber which I can't do without cause head/intake alignment issues. So taking off another .025" from the head for a total of .030 would put me at about 60cc head chambers. Take off another .010 for the thinner gasket and I'm at 59cc and add the 4cc for the pistons that puts me at about 10.8 for compression.

I know I'm gonna fall short of that goal of 11.2 simply due to the fact I can't take off enough metal but since I've got stronger internals now I can up the shot from 150 to 200 to make up that difference.

Can anyone give me a little help confirming my math is either wrong or right. I feel like I'm doing something wrong so a little help would be much appreciated. This is a stock stroke motor still btw.

74u

iTrader: (9)

This is what I always use...

http://www.csgnetwork.com/compcalc.html

...do you have accurate numbers for all fields?

SoonerBrad88

iTrader: (15)

Well according to that calculator I will need 56cc chamber to get my 11.0 compression haha. But if I mill the heads a total of .035 and get 59cc chambers according to the calculator it will give me 10.7 compression. I could live with that for sure

JimMueller

iTrader: (9)

If you have Excel you can try the link in my sig. You need macros enabled to allow all functionality, but I can send you the real file if you PM me your e-mail address.