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Thread: O-ring heads?
11-21-2020, 12:38 PM #1
So I'm yanking my heads to have them checked over. Oil burner on cyl 4, buildup on back side of valve. 1800 miles only 1800 miles on them since being built fresh.
Educate me on low profile fire rings for combustion gasses. I'm looking at having receiver grooves machined into my head's while they are off. No receiver grooves on block side. Fire rings will seal against the MLS gaskets. Really don't want to tear down my lower end for block work. Stainless vs copper? Solid vs hollow? Reading they should protrude.005"-.007"
Yes, no, better way?
Iron block if it makes a difference
Last edited by painlessauto; 11-21-2020 at 01:03 PM.
11-21-2020, 02:08 PM #2
You've got all the specs correct, Matt.
The challenge with the install model you are looking at is the malleability of the aluminum in the heads. The problem is similar to putting stainless o-rings in the block and receiver grooves in an aluminum head. The copper gasket is harder than the aluminum head and will mush out the receiver groove in the head ultimately causing a gasket failure.
If you just reverse the order of battle and put the stainless o-ring in the head and the receiver groove in the cast iron block deck (or sleeve flange) the assembly seems to last forever even with repeated assembly and disassembly. Similar phenomena (and fix) just a different arrangement and type of sealing components.
11-21-2020, 02:21 PM #3
What about putting stainless wire in the head and no grooves in the block. Only have the wire protrude .005" or so and seal against the MLS gasket?
I'm planning on staying with Factory or Cometic MLS gaskets
Last edited by painlessauto; 11-21-2020 at 02:32 PM.
11-21-2020, 10:44 PM #4
There are lots of combinations that can work with varying degrees of success, Matt. Normally the tried and proven approaches are the conservative best bets. That doesn't mean that other variations on one or more themes may not have positive results. Generally speaking the stainless wire and MLS gasket combination is infrequently used. That doesn't mean it will not work. The flip side of the coin is that if it did work you would expect a small group of advocates promoting it for the sealing benefits it offers. To my knowledge that group does not exist.
Should you give it a try? Maybe. If you are feeling adventurous and don't mind potentially tearing the engine down again if the experiment fails there is no reason no to give it a whiz bang. On the flip side of the coin if it fails, you can not just remove the stainless wire and continue to march. It is probably a new set of heads or escalating the gasketing to a larger wire diameter and the use of dead soft copper head gaskets.
For street cars, by and large the MLS gasket does a very credible job. If it is failing in service I would look to make sure all surfaces are flat, true and meet the micro-inch finish recommendation the particular gasket manufacturer asks for.
You should be able to seal up a street driven car fairly easily with MLS gaskets,
11-22-2020, 01:04 PM #5
Good info Ed. I haven't had any issues running 25-26# boost with the 2.9 Whipple setup on the street. I figured I would explore my options since the heads are coming off anyway. I guess I'll leave well enough alone seeing how my twin turbo setup will likely see slightly less boost.
11-22-2020, 01:15 PM #6
Turbo applications will hit the gaskets more gently initially. Certainly at high boost the stress is considerably higher but the dwell time that the gasket sees the boost for is very small because of the elevated rpm. As a result the gasket life is much better than you might at first anticipate.