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juan ruiz juan ruiz is offline
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Join Date: Jun 2000
Location: Florida
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What I was told, back on the day. from another of my High output 911 Gurus

Flame rings have been around for eon's in the racing world and are incorporated into a very high percentage of racing engines in some sort of design or another. Many blocks/heads won't accept an interlocking groove and must suffice with just a beefy o-ring in a head gasket, but the interlocking groove is by far the most secure.

Cosworth actually runs a groove all the way around the liner with an escape path to the ambient air to release any pressure between the heads/block to keep it from lifting...

The 935's all ran a Ni-Resist flame ring, and they kept the engine's together, but tend to still leak due to the mismatched expansion rates of the materials and inability to set the tolerances correct for both cold and hot running conditions.

Early on, we tried the Ni-Resist and Stainless rings, but when set tight enough to stop the leakage, you would crack the liners due to them remaining small as the liner expanded due to heat.

There are many copper rings placed in aftermarket head gaskets, Porsche's used many types of sealing rings in the liners, from covered springs, to graphite materials, but they all have their limitations.

The only thing we've found to go the distance has been our flame rings, interlocked between the head and the liner, fit to a tolerance of 2 ten thousandths of an inch. any looser and they leak, any tighter and they gaul, stick and break things.

On 964/993 heads, you'll go right through the heads when installing them as the fins protrude very far under the surface of the deck, so the face needs to be rebuilt as a solid supporting surface.
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Old 03-04-2010, 11:47 AM
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