Thread: Cylinder head question- Pat or anyone

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I have a .030 over 454 with flattop pistons. Sadly,they are .032 below deck. Even more sad is the 215 heads that I have cc'd are a whopping 117cc!!! Stock, they are closed chamber at about 101cc but they have been ported, bigger valves and shrouded. The unshrouding added cc's ...16cc to be exact. I put this on the desktop with a .021 gasket and only yield 8.4 to 1. If i shave .030 off the heads, about what would be my new cc chamber volume? Is there a way to find this out? I would like to get about 9 to 1. I also have 781 heads but i cc'd them and found a worse 119cc. I would like to use the 1968 215 heads because they have 2.19/1.88 stainless valves, and about $1400 of port work and 4 angle. With the low compression, I would probably be better off with the 781's but i would rather get the compression up as much as I can without changing the piston. Thanks for any input.

o deck the block . 16 cc may happen on the heads i set them up on the mill and cc them and cut them and re cc them . you would have to give them a cut to know. i can not tell you much on this. not seeing any thing but i think i wound go at the block i would say you have more than 17cc right there just did the big valves in a 402 head 113 is now 103cc with a .015 cut and the big valve allmost all the time fill up volume less they are sunk

you can cut .030 off the heads but that will not help the piston being that low in the block the bore is round and would be easy to find out the cc but the camber is not as easy that is why i said i cc them and then cut them and cc them

how are you cc? with a plate on the head or a pointer if a pointer o set it add .030 down and cc the head and see where you are or tape a 025 to to plate and cc up to it this may not work good with the plate but you can try

I thought about using the 292, 113cc heads off my 402 but that would only raise compression just a bit. I was trying to avoid disassembling the shortblock. I think for the ease and cost, i will mill no more than .030 off the 215 heads. They have never been milled before. Do you think there might be any geometry problems? thanks

I have been using a plate with seringe. I have done it many times just to verify it. it seems to be correct.

no should be ok the intake ears the bolt holes of the intake . them bolts holes may need a back trim on intake side with a file they may hit the valve cover rail if the intake as the top bolts on it

is there a ballpark for a specified amount shaved off the head, a corresponding amount of compression increase?

well if you check every chamber so you know what you have in cc there are formulas i do not use them i cc the heads. i do not see how you could go by math and not to verify by cc them? i do like i said works the best for me i know what it is when i cc it there is no mistake i add the head gasket cc and the head cc and the piston cc andwork from there the desktop dyno will do it for you or the moroso and keith black piston and there are math formulas to if you cc down .030 from a pointer this will tell you your new cc without cutting the head . the head has to be dead level .and add up your cc

thanks for the help Pat

Originally Posted by flanker1970

thanks for the help Pat

ok i would make a pointer nothing to fancy just needs to be level and .030 down in the middle and fill to it to the low point flat plate of steel or any thing that is flat and add a .030 point paper clip needle welding gas rod and filler back up

will do thanks again for your advise Pat

Flanker....ballpark figure is on big block heads, you have to flat mill about .005/.006 per cc. I have a set of 291 rect. ports on my 505 now that have been milled .042. No fitment problems with the intake, but any more, and I would have trouble. You can always have them take an equivalent amount off the intake side of the heads also. Your machinist will tell you what is best. I used the .005/cc figure when I brought my heads to the machinist, and it was just about dead on. Remember also, milling the heads that much will also reduce your piston/valve clearance, but not as much as your cam choice. But it's something to think about. As Pat said, it's the block deck hgt. that's killing you now. But I also agree that pulling it all apart to do that is a pain at this time. If you do that in the future, then you can not only have it decked, but get rid of those stock pistons and get something that can build some compression with a larget chamber head. The small chambers are good, the 215's are great heads, but they're getting harder to find. The large chambers, like the 781's, much more common, but you need a dome piston to make them work well. I'll do some figuring and see how much that milling will help. I dont think it will be too much of a difference though. John

OK, using your figures, I actually get about 8.1 with your current heads. If you mill them .030, and reduce your cc's by about 5 or 6, you'll only gain a little...gives you about 8.4/1. Still not anywhere near where you want to be. And that's with a steel, .020 head gasket. You cant really gain any more without doing the engine over. Sorry! But, 8.5 or so isnt the end of the world either. Just cam it properly, and it will still be a strong engine. Or save up a little more, and get a Pro-Charger for it!!!!!!!!!!!! Oh, and I cc heads the same way, with a syringe. I use alcohol with a little food coloring in it. If you measure carefully, it's very accurate. John

a lot of mills can not cut the intake side with the oil rail is in the way so cutting the intake is one way to go my big mill will not do it ,the cutting head is to big you could and i have cut them with my bridgeport mill with a small 4inch cutter head yes .005 a cc is close but i have seen guys hit the head hard with the wheel and say that it is o when they chop off 1/2 of 0.005 and more cuts the more you will be off the mark that why i said i cc them a cut i did some work on some heads they where stamp 115 cc the guy said that is what they must be ? i said no lets cc them i did and they where not he did not want me to cut them and change the cc but he blown the head up and it needed to be welded so they got cut just trying to say you can not put it back on when it on the floor so i am carefull on milling