Milling 452 heads

[73cudakid]

I know this has already been talked about most likely but here goes anyways. I have a set of 452 heads from a 400 that i would like to mill so that the cc are closer to 78-80 ccs. I believe that in stock form they are closer to 88-90 ccs. Im going to cc them to be sure, but how much can i mill off without affecting the valvetrain geometry. I read somewhere that it would take .0042" for every cc on the head and .0123 for every .01" removed from the head on the intake. So is roughly .05" from the head and .06" from the intake too much to be safe??? I can find some of the info from other websites, but i dont really trust them...Id rather here from the guys that have done this. Thanks in advance.

[moper]

It's more for an Mopar open chamber than the .0042. I use .004/cc for closed chamber heads, and .002/cc for open chambers. Honestly, the quality control on iron is so poor, the only way to get it perfect is to measure, cut, and measure again.

[HP2]

No doubt. The last set of heads I built had varying depths in the chambers, as cast. To get proper squish I had to mill some and leave others alone.

[Kapteenikosmos]

It's more for an Mopar open chamber than the .0042. I use .004/cc for closed chamber heads, and .002/cc for open chambers. Honestly, the quality control on iron is so poor, the only way to get it perfect is to measure, cut, and measure again.

Can anyone confirm those numbers? I've been living in belief that 0.004in/cc is for open chamber? My block and heads are in machine shop right now and the amount I told them to mill from heads was based on that 0.004in/cc  . I also measured the chambers before they went to machine shop and got ~94 cc from four different chambers. Bit high but possible? My heads are also set of 452.

With very good luck they haven't started the milling yet and I can call them with new numbers tomorrow morning if that 0.004in/cc is wrong, otherwise I might end up with pretty impressive combustion ratio (I also have +6cc dome pistons from KB) 

EDIT: Just checked how much milling it would need to get 1cc from perfect round chamber ie same size as biggest bore in factory mopar. I'm guessing that the combustion chamber diameter isn't much larger from that. Seems like the 0.004in milling with assumed 4.34in "bore" in head (it isn't perfect circle but close anyway) will give something like 0.95cc. So I have to assume that the 0.004 is correct for open chamber heads?

[moper]

Edlebrock's spec for closed chamber 84cc heads is .0043/cc. Indy cylinder Head's spec for heart shaped closed chamber is .004/cc. A full diameter chamber will need less cut to get the same result. I couldnt ever find an exact, and to be honest, I've never compared resulting cc readings with milling amounts to figure it out. I can get you small block open chamber values shortly, but big block ones may take me a while. My heads (452s) havent been  flow tested yet, so the milling and cc'ing isnt going to be anytime soon. every chamber will be a hair different anyway because of casting. So really, you could go with the .004 deal, and figure is they are too small, polish the chambers.

[73cudakid]

I drew up the cylinder here at work in cad and found the volume of the cylinder, which a 4.34 dia at .0042" height came out to be 1.02cc, so i think that should be good. Im just not sure what the max amount that can be taken off before the valvetrain geometry gets screwed up. Im trying to avoid shims, special length pushrods, etc since this motor is gonna be down and dirty with as much power as i can get for the least amount of money. I can get my heads milled for free or damn close since a friend is a machinist on the night shift.. hehe.

Thanks again
Dave

[moper]

That amount is different for every engine out there. A safe bet to assume is about .020. That doesnt get you much if you're looking to get soem squeeze. SHims are easy. If you mill .040, you add .040 shims under the shafts. The best way in any build is to use a couple checking pushrods and get the rocker geometry right, then order the ones you need. In terms of your calculations, the chamber is not the size or shape of the bore, and the walls are tapered, not to mention the casting surface is lumpy and can contain shapes from casting, so your formula is off already...lol. If you are to mill, check the preload before you decide against shims or anything...

[73cudakid]

Im gonna go with the shimmed rocker shafts and go with the milling i talked about earlier. I used the 4.34 bore since it was the largest of the stock big block bores to see if i was in the ballpark...thanks everyone!!