Compression Ratio With O-Ring?

Well I am back from Hawaii, it rocked, and I have decided to o-ring my heads and intake. The question I have is, how do I calculate compression ratio with an o-ringed head? Would I just eliminate the entire gasket thickness calculation?

Hunter

Nope, there's still a volume that will depend on the compressed gasket thickness and the diameter of that gasket bore.

If it's say, .030 thick when compressed and the gasket bore is 4.1", then you have ~6.5 ccs of volume in that area between the block and the head.

-Mindgame

But since I am not using a gasket, how do I calculate that?

Maybe I'm missing something with O-rings but isn't just the o-ring and nothing else?

Hunter

There is still a gasket, but the O rings help prevent the gasket from moving around and blowing out on forced induction applications.

Thanks taht exactly what I need to know...any reccomendations on what gasket I should go with, 20-25 psi of boost from two turbos is what I am dealing with.

Hunter

The purpose of the o'ring is to increase the clamping load around the cylinder bore. If the builder is going this route then he'll use a copper gasket of a specific compressed thickness. Find out what the thickness is and you can run your calcs.

With the o'rings, I'd go with a Clark or SCE copper gasket.

-Mindgame

Don't forget to use a good gasket dressing.

My engine block is o-ringed, is there a reciever groove that is needed in the heads as well or is the machine work done just to the block?

The reason I ask is I want to run a set of heads that are for a temporary setup. The heads are a buddies and I really do not want to have them machined since his setup does not require o-ringing. The engine will be N/A. Is it possible to just have the ring in the block and just run a copper gasket and work correcty?

Also there is always talk about o-ringing a setup that is going to be used on the street or as a daily driver. Is it incorrect for street use?

Yes, you can do it without grooving the heads. I would expect a bit of indentation on an aluminum head though.
Alot of guys just ring the block.... although most of them got by fine on composite gaskets until boost pressures started exceeding 20 psi.

I don't have a problem with o'ringing for a street car but the use of copper gaskets can lead to some problems if the deck surfaces aren't prepared with them in mind. If you have an engine builder experienced with this type of build around, give him a call and see what he has to say. That or find ean engine builder others have used for similar builds. That's what I always do.:)

-Mindgame