I have been making copper head gaskets for several years and am pretty well
"self-taught". What I have found out is that ability to seal any flange (in
this case the block and head) is dependant on a some very important factors:
#Flatness/Tureness
#Surface Finish (Roughness average (RA) measured in microinches)
#Clamping Force
Suffice it to say that copper gaskets work better when the surface finish on
the deck and head are about 70 or so. To give you an idea of quality of
finish -a # of about 10 or so is smooth as glass and about 100 is about the
finish that most early engines are milled at. This finish is the arcing
concentric lines that you can just appreciate with your finger nail as you
perceive the "hills and valleys" of a freshly milled head. Under a
magnifying glass this looks something like a sawtooth configuration. So...a
standard gasket (fiber or multilayer copper/asbestos/steel shim) will
configure itself to this irregularity and "seal". A solid copper gasket
could make this seal if it is thin...but if it is too thick it MAY not.
I've made solid copper gaskets at .125" for many cars primarily to decrease
compression once the head has been milled too much. Sometimes it doesn't
work. Aluminum heads need a different spec than cast iron heads..
The clamping force is the axial pressure generated by the fasteners. The
bigger the fastener the more "torque" can be applied and hence the more
clamping force...
Sounds good BUT--the clamping force is just a small percentage of the
torque. I've read that it is about 20% of that #. Most people think that
more torque is better. Not true. The more axial tension the more distortion
is placed on the cylinder and it will deform...especially at the weakest
points -the waist and the top. This will cause -dynamometer prooven-
horsepower loss.
There is a lot more of this stuff--- on my www page. on the what's new or
physics section.
www.headgasket.com
Mordy
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