How much can 390 heads be milled down?
they are 72te heads.
will be putting in bigger intake and exhaust valves, and also port and polish.
and after i mill the heads will the intake need to be milled also?

 

It is better to use pop up pistons that do major head cuts. Two reasons, first if the high compression does not it work out, putting material back is real hard. And the biggest reason is if you cut the head a lot, then you have to cut the intake and then it is no good on any other engine.

 

You should look for a pair of '67 or '68 390 GT heads, I think they have smaller combustion chambers and bigger valves. Most real truck heads have heavy valve rotators which helps for endurance in heavy trucks but are heavy and limit the usable rpm available.

 

The 390GT head is exactly the same as the standard heads except for the staggered exhaust bolt holes.

 

Or, cut the intake side of the head, and use RTV at the end-seals.

 

The cutting should be done only by a well qualified machinest in a good shop. If not you could end up with a real mess and no recourse.

 

That can be said about ANY machine work.

 

That is true, but most peop[le just accept that a machine shop is a machine shop and they know what they are doing. HA!