head shaving

[sparkyzx2]

ok guys i fried my head gasket so i have to get the head resurfaced........... so my question is what kind of power gains would i get if i had it shaved down a bit and how much should i get it shaved???? or would it not be worth it??

[mechtech]

As little as possible to get a true flat surface.
You want as much meat as possible, for anti warping and heat dissipation reasons.
There will be small gains from milling, but if you go a lot you may need premium fuel and possible tuning.
If you have aftermarket hot cams, then consider going after high compression. For stock or near stock, be conservative.

[iceracer]

As with all modifications, except forced induction, gains for each are small, but they add up. A slight increase in compression will also help with gas mileage,a little.

[Thnikkaman]

great advice. a 0.040" mill will get you to about 10:1 compression. 0.070" will get you to about 10.5:1. You will hear people tell you that 0.040" will get you to 10.5:1. this is incorrect. It is based on an estimate assuming a cylindrical combustion chamber. We do not have cylindrical chambers, they are almost square at the base and dome shaped. I have measured CC volumes before and after a 0.040" mill and i did not get to 10.5:1.

you will slightly increase the risk of detonation from removing head material. not only from an increase in compression but from changing the quench areas around the edge of the piston. i have been at about 10.2:1 (head mill + thinner head gasket, stock pistons) for years now with no problems on 91 octane gas. I do have hotter cams, headwork and lots of tuning though.

also note which head gasket you order. Ford has homogenized the part numbers between the escort and focus. You will now get a thinner 3ply (0.020" thick) gasket when ordering a zx2 part. A few years ago, you would have got a thicker 4-ply (0.035") gasket. you can still get the thicker one by ordering a focus svt gasket. the zx2 from the factory had the thicker gasket.