resurfacing gt 40 head question help

[stangaddict2007]

Got a set of gt 40 heads completely redone on ebay from a machine shop heads looked good to me ,my mech. at ford noticed a spot on mounting surface that you could catch your fingernail with. we went ahead and installed them on a new 306 short block ,made it 250 miles when white smoke came out exhaust {antifreeze} pulled plug on suspected head and found coolant on plug, up to that time I was having a coolant problem with coolant bypassing rad. cap, we figured piston was forcing pressure into coolant system. The bad ebayer suggested i have head cut down again my question is do i have to do both heads or just the bad one thanks 4 any help mike

 

[Fox8950]

Milling down a head is going to change compression a little bit (not sure how much your talking about going here) so it'd probably be best to match them. Not sure how much you could mill off w/out it mattering.

 

[Gearbanger 101]

You pretty much need to do both heads. Not doing so will misalign your intake manifold to your new head and could cause all kinds of issues. If it's only a .010-.015, you might just get away with it, but either way most shops will charge you the same price to do both and it's extra insurance to ensure the deck surface is true on both head and you don't have this problem again.

Yes, it will change your compression some, but we're talking less than half a point here. Not enough that you'll notice a huge difference. Try to keep it .030 or less if you can. Any more than that and you may have to mill the intake down as well for it to properly seat the gaskets. As it is you may have to elongate the intake bolt holes, but that can be done with a rat tail file and a little patience. But you won't know until afterwards if it's necessary.

 

[PUNISHER RACING]

I would have them pressure checked and magged before you do anything to them sounds like they have a crack in the deck, also get them both checked