8445 heads milling whats the max that can be removed and still be okay?

[farmer Gary]

I have my oil test heads #8445s at the machine shop to mil the deck surface for optimum head gasket sealing. head deck felt smooth as glass with some dark spots, rust. after cleaning head surface with dilute phosphoric acid , you can feel where the rust dissolved with your finger tips. Machine shop called and after milling .002" 2 thousand's off the said they still had several pitted areas primarily around the fire ring seal area.

I have two main questions. 1. how much can be milled from the head deck and not cause any problems?
2. how to measure how much has already been milled from the since it was first installed?
I could not find any post about the first question, for the second I read something about cc the combustion chamber volume to guess about how much had been milled from the head as the combustion volume would decrease the more that was milled off.
I'm sure the machine shop does good work,just not much on Buick engines. i got the impression that 2 thousand's off was a lot, from other posts I have seen, 6 thousand's removed at a time to clean op the head surface is not uncommon?
once I find the photos of the heads before any cleaning was done i will post them.

 

[Mike T]

The heads on my car are the originals. They have been cut at least 4 times over the years. Back in the early 90s they were cut .020 because the machine shop treated them like all of the other NA stuff he worked on.

Since then they've required resurfacing 3 more times that was actually necessary. I can't say for sure how much has been cut off but it's to the point that the intake bolts barely fit.

Otherwise I haven't seen any adverse effects.

.002 is nothing IMO

 

[BEATAV8]

.002 is not a lot for surfacing.
You can always get custom thickness head gaskets if you need.