Head Surface for sealing

[karolko]

I just got back my 8445 heads from a local machinist, for a leaky valve.

Anyways when I picked up the heads he told me that he checked the heads and they were only 1 thousandth out on the milled surface. when I looked at the bottom of the head I noticed they had sandblasted the chamber and the milled surface.

I asked him if this is still going to seal as I was worried it wouldn't be smooth enough and he said yes, BUT I am unsure and want some expert advice.

The heads have already been milled down so trimming some more off is not something I want to do unless 100% needed, but at the same time I do not want something that will not seal either.

Thanks for the help guys,

Adrian

 

[earlbrown]

If you're using anything other than steel gaskets, you're most likely fine. If you're using MLS gaskets, then maybe.

 

[karolko]

Shit I am using Cometics...

 

[earlbrown]

In that case, get a large diamond stone and some WD40. Do a couple of large circles and see if you have any low spots. (common places are between cylinders and next to water ports at the fire ring)

or if you have a large glass table, clean it and affix a couple sheets of fine grit to it. Same as above.


If you find any low spots, you need to find a machinist with a good surfacing machine that knows how to prep for Cometics using substandard fastening arrangements.

 

[PSID6]

I can see blasting the chambers to have a nice surface to do your valve job, but after milling the heads. C'mon

 

[karolko]

Yeah I am not too happy. I will be sending them back to get resurfaced, but that means thicker gaskets in my particular case. Just another day in the life of a buick owner.

 

[PSID6]

Why ? Where are your chamber cc's? Since they have already been milled it shouldn't take more than .003 thousandths to clean it up