When I warped my BMW head, there was a factory spec for the thickness from the valve cover gasket surface to the head gasket surface - I wasn't supposed to deck it more than that number or Bad Things would happen.

I have not seen a similar spec for Olds heads.

Is there any valve gasket to head gasket surface spec that I should be aware of?

I ask because I have a set of B heads I might be decking a bit, but someone already machined some amount off of them - if I had a spec, I could tell how much, and whether I needed to take any more off. Without it, it's kinda guesswork.

I have already cc'd it (a bit inexpertly) and gotten roughly the specified volume (about 82 or 84cc if memory serves), so I believe they only cleaned up a few thousandths.
My intention, when I get a round tuit, is to remove roughly 0.030", which is the difference between the stock 0.016" steel shim head gasket and the run of the mill FelPro 0.046" gasket, thus maintaining proper geometry and orientation, as well as compression ratio (specified at 10¼, but from all I've heard, probably actually 9¾ or 10:1, which should be manageable on 93 octane and the right cam).

Thanks!

- Eric

 

yes i dont have the book in front of me but i believe the btr and mondello book specify the correct thickness. The combustion chambers always vary a little from what i have been told.

 

I'll check my Bill trovato book. I don't remember seeing it in there (and I did read it cover to cover ).

- Eric

 

If not i will find it in know it's gotta be in one of those books i have read both and overtime they kinda meshed togetehr lol. If no one chimes in i will find it and post.

 

The Mondello Olds V8 Technical Reference Manual says you measure "the distance between the head bolt boss and the deck surface of the head" (pic shows a dial caliper measuring this). Book continues....."If this dimension is less than 2.200", then most likely the surface of that head has already been milled at some point. The average stock measurement for an OEM head is 2.200" - 2.220"

 

So, with typical GM precision, there's 0.020" tolerance in the spec.

Sounds like a reasonable tolerance, though, considering they were using hydraulic lifters, which can accommodate a 0.020" variation.

Thanks, Patton! ... And, yes, that's the book I don't have.

- Eric

 

X2

Also in the Wild About Cars "Engine Modification and Tuning Guide". They mention heads shouldn't be milled more than .060