How far can late 70's 400 heads be milled w/o causing intake/exh. manifold issues?

hi
more than .020 and you will need to mill the intake side of the head so intake wil fit.


ex side should not be a prob .

for a start I would mockup & check the "height" of the "V" (bolt hole alignment is an OK check for this on a DD) & it sounds like this is a stock rebuild) & for sure see if the surfaces (head/intake) are FLAT. vac leaks are the cats' a$$. check/mill em flat/mockup/THEN use the right thickness gaskets to get everything in the "V" lined up adequately. to Keep It Simple Sam, a slight milling should present no problems but do mockup & go from there.

Found this years ago don't know how accurate.

http://www.mopar1.us/mill.html

Putting aside all intake manifold fitment issues, most people would tell you 0.060" is the max. However, a few years ago we had a member who had milled his open chamber heads far enough that they became closed chamber heads. I think that was 0.080" or 0.090". As I recall he opened up the top side of the ports in his heads and didn't cut the manifold.

R.

I've seen 0.090" too. I assume he enlarged the bolt holes too if he did not mill the intake port side of the head or manifold.

The 0.00123:0.001 ratio is correct.

that is the formula i have always relied on as well. also, have seen up to .060 cut without cutting the manifold face. but that was way back in time when heads were new. now days, the only sure fire way to know, is to dry fit, then go accordingly. even with new heads. just my opinion.