I searched on mill and milling and didn't find anything that I'm looking for. I'm researching building my head. Since I don't have the money to do the bottom end right now, I was thinking about milling the head a little. My question is how much compression do you gain from say milling the head .010?

The thing is, I will build the bottem end in time with higher compression pistons and I don't want to have the head milled too much and then it bumps the compression up even more and then run into problems running on pump gas.. btw, my motor right now is a stock JDM ITR motor, with I/H/E just so you guys know where I'm starting from..

Depending on how much compression the milling gives, I can come up with a greater overall plan for my motor. Maybe something I can do in the mean time to build more power but won't affect the build as a whole when I get into the bottom end.

Thanks H-T.

 

I wouldnt bother. ITR already has 11.1:1

Check out:
http://www.zealautowerks.com/index.html

 

Be sure to clay the head to check your piston to valve clearance if you mill the head.

 

Thanks for the link. Very helpful and useful!

When you say you wouldn't bother, you wouldn't bother milling? or changing the pistons? I was eventually thinking something like the Toda, 12.3:1 pistons.

The calculator gave me a bump of .32 in compression from milling the head .010, maybe I could do that for now and later do something like 11.5:1 pistions? or maybe even just leave the stock ones and do a thinner head gasket with the milling..

Actually, let me ask this, what would be stronger for the motor? Just changing the pistions, or milling and using a thinner head gasket?

 

second that .3 for every .010milled off

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rainforest &raquo;</TD></TR><TR><TD CLASS="quote">second that .3 for every .010milled off</TD></TR></TABLE>

That is a rough approximation and for most is sufficient, but understand that shaving the head and the reduction in CR is not linear. The smaller the combustion chamber is, the larger percentage of volume reduction from shaving .010" In other words, the 1st 10thousanths may yield a .32, but the next 10thousanths may yield .35, etc.

So if you are running a high compression piston (ie. 12 or 13:1), then your chamber volume is much less than a 10:1 chamber, thus that 10thousandths head shave will increase CR more on a 13:1 piston than a 10:1 piston.

 

What I would recommend is estimate the volume reduction. If we assume the circumference of the chamber on the head is 81mm, then shaving the head would yield the following volume reduction:

8.1cm^2 X Pi/4 X .0254cm = 1.31cc
where .0254cm=0.010"

Now you can use the C-Speedracing Calculator and simply reduce your "chamber volume by the appropriate volume.

http://www.c-speedracing.com/h...c.php

Volume Reduction:
0.010" approximately 1.31cc
0.020" approximately 2.62cc
etc.

Now if someone can actually measure the diameter of the head chamber, we could improve the accuracy. Perhaps that head chamber diameter is 84mm, that would bump the volume reduction per 0.010" from 1.31cc to 1.41cc