WOW
A subject in which I can contribute.
The cylinder head gaskets that Dick mentions, even though brand "X", are
referred to as Metal laminated steel, the latest in sealing technology,
(actually it is not new. It is preceded by Coopers rings and other devices
that provide a high unit load at the combustion seal.) Ford began using MLS
technology with introduction of the 4.6 L Modular V8 in 1992, as a 3 layer
gasket. I remember a representative of Cherry Gasket Co. in Japan
approaching me with this technology in 1986 when I was the component design
engineer on the 2.3L 4 cyl engine at Fraud. He had in his hands a gasket
from the then Honda F1 engine, and it was a piece of work. Actually 4
layers.
but then it is a different story. (a real gasket engineer would wet his
pants just looking at one)
These gaskets are embossed, and coated with an elastomer material for micro
seal of fluids, and are NOT REUSEABLE. They generally also require a very
smooth and flat surface, with very little variation. Old Rz and Ra surface
finish measurements are not sufficient for most MLS gaskets in use today.
On the up side, they work extremely well when all design requirements are
met, and provide less bore distortion than conventional solid core gaskets
with bore grommets, and wire ring inserts. I have been using high pressure
gas filled "O" rings for sealing combustion gasses on my boosted engines,
and if MLS gaskets were available I would not bothered. They are generally
speaking that good.
Recently the two layer gaskets are an effort at compromise in cost. Even
with the 3 layer, there were only two companies that truly had a handle on
design and development of this type of gasket. Within the Ford supply base,
Fel Pro, and Ishakawa, were the only ones, and of that the Japan supplier
did not have a US facility, nor would they commit. The design of the
combustion seal is critical. There are several approaches, and none are
necessarily wrong, just some better than others. For proper design intent,
look at the early ford part and proceed at your own risk. As we all know,
clamp load, and consistency of that load is also paramount, and I worry more
about that with the standard paper faced gasket more than the design. The
real advantage of MLS is that the Joint then becomes metal/metal, and there
is virtually no creep relaxation thus equal clamping load for the life of
the joint. Torquing to a predetermined point on a fasteners stress/strain
curve is possible, with predictable load, and life. I don't advocate torque
to yield for our racing applications, but we can know where we are and what
we are doing at this tenuous sealing joint.
Sorry if this sounds like a lecture. They used to call me professoria in
Brasil..... :=D
Rick
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