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O-ring vs. Headgasket?


PanzerAce

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So what exactly to people mean when they talk about o-ringing an engine? I *think* I get the basic concept of using o-rings instead of a gasket around the cylinders, but what do people do where the rest of the head and the block meet? And how long do they hold up?

 

Thanks for the information.

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When you O-Ring the block you use copper head gaskets and coat them with a sealer like Holimar or some people use RTV silicone. This seals the copper head gasket to the block to prevent water from leaking in the cylinders etc.

 

The O-Ring goes around the cylinder and puts a groove in the copper head gasket to seal the cylinder for compression If you look at my website jnjdragracing.com under engine pictures you will see my block with O-Rings.

 

If you plan on running alot of compression like we are now you need to O-Ring the cylinder heads also.

 

Some people use Cometic head gaskets which are supposed to be good as O-Rings, I have some Turbo friends that use them opposed to the cost of O-Ringing.

 

I hope this answers your question. You can search the internet for maybe a better example.

 

John

 

e=PanzerAce;934211]So what exactly to people mean when they talk about o-ringing an engine? I *think* I get the basic concept of using o-rings instead of a gasket around the cylinders, but what do people do where the rest of the head and the block meet? And how long do they hold up?

 

Thanks for the information.

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O-ring when you know your tune and what your doing. This setup will keep nasty amounts of boost at bay, but, it will also keep nasty amounts of knock, dedicated to the combustion chamber. You judge your own level of skill.

 

 

Sounds like everything else... there are pros and there are cons.

 

when O-ringing, does the copper gasket stop short of the O-ring and the steel O ring hold the cylinder pressure in, or does it fit over the copper gasket to increase the clamping force above and beyond what pressures the copper alone can manage?

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Go with the steel gasket. i've blown an o-ringed copper gasket, but had no troubles with the mulit-layer steel. Yes, it saw some knocking and boost!

 

You did not set it up correctly then. A solid copper gasket will outlast a set of pistons when it comes to detonation and boost, IF and only IF setup correctly.

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This wasn't my first go around with building engines. This blew my mind, as well as the gasket! Before tearing the engine down, I rechecked the head bolt torque and it was right on. When I pulled the head, both the block and head were flat. It didn't blow right after a rebuild either, as it had 10,000 miles tearing it down. The engine wasn't torn down to add a ported head and that is when the gasket issues were found.

 

Take it as you may, but the gasket failed before the pistons. The pistons (stock ones) have been ceramic coated with techline coatings CBX, which seems to be some pretty decent stuff. The only thing that I can figure is that it kept the pistons cool enough, that they could stand the detonation. I am guessing that the temps the pistons would normally run at high boost and detonation would be enough to soften the aluminum a bit, leading to piston failure before gasket failure.

 

Looking at the gasket, the copper deformed away from the combustion chamber far enough for the o-ring to fall into the chamber. It moved maybe 3/16-1/4" making the fire ring egg shaped. It didn't blow far enough for combustion to be directly leaked into other chambers, or into water. This happened on three other holes as well, almost to the point that the o-ring slipped out.

 

There was lots of evidence of detonation on the head, and the rod bearings were beat pretty badly as well, but the pistons faired pretty well. Well enough that they are still running in the same engine.

 

On a side note, I annealed the rings on that last build by over-using the anti lag feature on the megasquirt. Sure is great to get the GT40 spooled up, but hell on EGTs. AFter this, there was enough blow-by that I thought I had broken a ring land. Pulling the engine apart again showed perfect pistons, just no tension left in the rings. Just some antedotal evidence, but seems as though the coating I used might be doing something.

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Heat that kills pistons is from preignition and you will never hear it, the things just catastrophically fail. The pressure trace is completely different than that of detonation. Though pressures are just as high, if not higher.

The pressure spikes of detonation are what breaks things, and I can't believe cast pistons withstood detonation or preignition that blew a head gasket unless something was improperly done in the head gasket application.

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I have had detonation/preignition (whichever it was) happen bad enough to break spark plugs, to the point the engine would barely run, or four different occasions with these same pistons. Yes, I was very stupid on my younger years with this motor, but sure did learn a lot. Still running the same pistons though. When one finally breaks, I am going to melt it down and make a lucky charm out of it.

 

Not sure about the type of copper used, whatever comes in an SCE gasket.

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www.techlinecoatings.com

 

the product was CBX, I bought it years ago. I don't think they sell it to the general public anymore, just shops. Could probably get one of the guys with a shop on here to do the purchase for you though.

 

I actually have a set of coated pistons, that I was going to use during my last rebuild (got them ready, as I thought I had broken a ring land). I ended up using the ones that were already there, as they were still good!

 

The coatings are easy to do, just follow the directions and bake em like cookies in your home oven. Open the windows though, as the oil residue that you can't clean out of the piston bottoms smokes up a storm!

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