Head Flatness

A

Alex Dragone

Member
I have a police head for my car (has a B cast in the top) and I measured the flatness on the bottom of the head with a straight edge and it is 5 thousands of an inch off in the center. Is this too much or should this be ok?
 
I'm just a shade tree mechanic, but I'd use it as is. Heads are more flexible than we think, and the gasket is going to absorb the difference. Torque in the proper sequence, and retorque a couple more times after driving it a bit. There's your free advice, for what it's worth.
 
nah leave it as is then just shave the head and change the gasket next month when it won't seal.

It is hard enough to seal a Model A head as it is.........
 
It's hard to understand why back in the day of nice thick copper headgaskets I don't recall any blown head gaskets on Model "A"s, and we used to pry them off with large screwdrivers and small crowbars, taking a file to both head and block after a difficult removal.... and we didn't even own a torque wrench - just kept them snugged tight. Are gaskets that different today ????
 
vermontboy said:
Are gaskets that different today ????
Click to expand...

That's what I was wondering. I took my head up to be checked. They said it was .002 out and recommended it be surfaced. I couldn't hardly believe that little bit could matter but I did it anyway.
 
When I worked on heads at the shop we set the limit at .005" for the length of the head and .003" for the width of the head. I wouldn't surface a head for being .002" out.

Model A's have quite a spread between head studs, so using a head out by .005" would be taking a chance.
 
I surface flat heads and manifolds on my table saw with some stick on sanding discs. I live on an island with no machine shop, but also I am cheap and enjoy doing things myself. I blew my head gasket using a head with 'speed head' cast on it. I surfaced a standard head and am using that with a graph-tite head gasket. No seeps.
 

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.002 is my guide as well I have my own van Norman broach and head / block resurfacing equipment . Piece of cake and like James said, why not for $40 and know its going to be good. I wouldn't be doing good work for folks if I didn't do it

I would find a machine shop and get it right. Yes, cast iron is flexible in torquing heads , but then why take a chance on sealing and issues when head gaskets cost are $25 plus
Larry s
 
Tom Wesenberg said:
When I worked on heads at the shop we set the limit at .005" for the length of the head and .003" for the width of the head. I wouldn't surface a head for being .002" out.

Model A's have quite a spread between head studs, so using a head out by .005" would be taking a chance.
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I,m with Tom on this one. Depends who and how they are milling the head. It might come out more than .005. It all depends on the cutter, and how they are holding the part down. It is not as easy as it sounds.
 
vermontboy said:
It's hard to understand why back in the day of nice thick copper headgaskets I don't recall any blown head gaskets on Model "A"s, and we used to pry them off with large screwdrivers and small crowbars, taking a file to both head and block after a difficult removal.... and we didn't even own a torque wrench - just kept them snugged tight. Are gaskets that different today ????
Click to expand...

If you look at the second picture on Vince's site you can see that
the area between cylinders 1,2 and 3,4 is narrower on the newer
gasket. I think that may be one problem. http://www.fordgarage.com/pages/felproAheadgasket.htm
Bob
 
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vermontboy said:
It's hard to understand why back in the day of nice thick copper headgaskets I don't recall any blown head gaskets on Model "A"s, and we used to pry them off with large screwdrivers and small crowbars, taking a file to both head and block after a difficult removal.... and we didn't even own a torque wrench - just kept them snugged tight. Are gaskets that different today ????
Click to expand...

Yes they are different now back in the day the 2 most common gaskets were solid copper or steel shim both worked very well but are now very hard to find
Next was copper or steel sandwich with asbestos filling which has very high temp resistance and also self sealing when in contact with fluids Banned today
 
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