Head Milling

[Krep]

I was wondering if anyone can help me out. I want to know how much I have to mill of the intake of a 400 for every thou. I take of the heads. Also what is a rough number of cc's dropped for every thou. Thanks.

[This message has been edited by Krep (edited January 31, 2000).]

[Challenger]

Krep

I wouldnt mill the intake but I would mill the intake side of the head. If you milled the intake then you would strictly have to use it for that engine and you couldnt resell it without making somebody upset with you and you can use the intake on another engine. What I would do is mill the intake side of the head, for every .010 milled from the cylinder head face, the intake manifold surface of the head should be milled .0123. As far as the cc rule, big blocks lose around about 2.5cc for each .010 inch. Taking about .050 inch will raise the compression over a point depending on size of engine. But really everything should be measured out. I would imagine that your heads have somewhere in the ballpark of 88 to 90cc.Best bet would be to have them milled to 80cc. Ill let you figure out the math. LOL

[This message has been edited by Challenger (edited January 31, 2000).]

[Old hippie]

I have had at least 30 sets of bib block mopar heads milled .0020 in the last 30 years and have never run in to any sealing problems with the intake manifold. Also no intake bolt hole alignment problems either.

The Old Hippie Hisself

[Challenger]

Ol hippie
My reply was a general answer. I am just relaying the dimensions from the Mopar Engines book. Should you mill more than .020 you will in liklihood have some sealing problems but it is good to know that at least we can go .020.

[Christopher]

Actually I've gone -.030 and never cut the intake sides of the heads and never had a sealing problem.

[Challenger]

Do I hear .040. maybe .050 how about .060.

[DartGT66]

.060" is no problem. If you go over that you may start having problems. In my current 318 project I milled over .080", and still believe it's going to work. The last two sets of '906' and '250' heads I measured were both over 90cc. Of course when you mill the heads you have to check the lifter preload, and adjust it if necessary. There are rocker shaft shims available for this purpose, or you can do like I did with my 318, shorten the stock pushrods. They are pretty hard though, and you have to have more than basic equipment for the job. Milling the intake face of the heads instead of the intake itself is absolutely wiser. The relationship in a big block is 123/100 like told earlier, and 95/100 in a small block.

[sixpackguy]

I have personally milled .070 off of 906 heads, also milling the intake side of the head as was previously mentioned, in order to not have a "one engine only" intake. One thing I need to mention is that once you get to the point where you take more than about .030 or so off BB heads, then you start running into a problem with the valley pan rails being too high, which you can only properly fix by milling them off some. Note that this comes into play after you have milled the intake side of the head.