Maximum for milling head?

[Defcon92]

Can you mill a head .080 safety? Will the head bolts still clamp safety? Thinking off pulling .080-.100 off my cylinder head for higher. Comp.

[akadeutsch]

If you mill that much off the head you will lower your Combustion Chamber volume by a couple of CCs without affecting your quench. I think you might be better off decking the block a little...say -.020. This way you will lower your quench enabling you to run a bit higher CR. If higher CR is your goal. I guess my question here is, Why take so much off the block? And what pistons do you plan to use? I know pistons don't matter because you are talking about milling the head only, but I would still like to know which pistons?

[akadeutsch]

Why? It makes more sense to me to deck the block -.020 and get a better quench as well as a better CR.

[IH 392]

Do you plan on running straight methanol?

[BADASYJ]

What a bunch of negative nancys you guys are, you just jump on the guy n tell him what you think he should do. Maybe hes not pulling the motor out of the jeep.
What the hell does running methenol have to do with anything IH. No way .080 would cause need to run meth. ASE certified machinist n you give an answer like that, what is that all about? Not a damn one of ya answered his question. No wonder this forum is so dead.......
Yes you can mill that much off the head n your bolts will be fine. You might need some new pushrods though.
I zeroed my deck n took my combustion chambers down to 53 or 54cc's. I believe somewhere around .100-.120 was taken off. I am not 100% sure how much was removed from stock.

[akadeutsch]

While CCing my 0331 head I inadvertently widened the C/Cs to 65 CC's. This would put my DCR down in the 6s so I had to find a way to make the C/C smaller. And there is only one way to do that. I am planning to mill .030 off. It sounds like this should work fine and it will take away 6-7 CCs out of the C/C.

[BADASYJ]

65cc is alot of room. I think 58cc is factory specs. Its gonna take alot more then .030 to get where you want to be. If memory serves me correctly i believe for every .010 taken from the head you lower the volume of combustion chamber by 1/2cc to1cc. Maybe some others can chime in on that n help us out.

[akadeutsch]

I figured my numbers using a 4 inch diameter cylinder. Since the C/C are not a complete cylinder I believe I will have over estimated a bit. But here is how I figured out 6-7 CCs. Volume of a cylinder = 3.142 x 2 x 2 x .030 = .37704 cubic inches = 6.17 CCs. Now it will be a little less because the cylinders are not round but I bet I will still loose more than 1/2 CC per .010 inches. I wonder if I will need new push rods. I will be taking .020 of the block as well.

[akadeutsch]

And I was reading my syringe wrong. As it turnes out I had between 58 and 59 CCs on all cylinders. I widened the dimple opposite the spark plugs on the smaller chambers to compensate and brought them all right around 59 CCs. I am comfortable here so I will tape it off for paint and spray it down with WD 40 until I can get some springs to build this thing.

[Defcon92]

4.2l stroker my way. Went 4.2 over a 4.5+ because the rod ratio & piston velocity issues that come with the bigger motors. Wanted this to last 300k like my stock jeep 4.0 did.

66cc chambers. 13.4cc piston dish (677cps). .033 quench using .051 head gasket. 9.21:1 static 8.05:1 dynamic. Ported 7120.
Ls6 valve train (less than half weight of stock 4.0)
1.7 rollers & mopar 230ab cam

Desktop dyno shows 258hp & 312ftlbs. Motor was built to last the long haul, haul the extra weight of a modified jeep. (Bumpers, gear, roof rack ect) Hopefully get better mileage than my stock 4.0 & be a lot more fun to drive.