7 replies to this topic

[Paul Vanderheijden]

I would be interested in hearing from anyone who has had experience with "coopers' rings for sealing cylinder bores, in combination with either a head gasket or with o-rings for oil and water passages.

[scooperman]

the only reference I have of the "Cooper Mechanical Joint" is in Hammill's book on Coventry-Climax engines, he says the FPF engines had compression sealing problems until they started using the Cooper rings, which had previously had been proven on the Vanwall engines. His description sounds like Wills rings, I don't know if these are two names for the same thing. Try searches for both names.

[Greg Locock]

Yeah, Wills rings is the name I remember. Most Ginettas that used the Imp engine had them, I imagine. Certainly the one I used to drive occasionally did.

[bobqzzi]

Are those the stainless gas filled o-rings? If so, I have used them and they work extremely well. We used silicone per Cosworths instructions and it sealed very well. In the US, they are made by Helico-flex which is a division of Garlock. I have the e-mail address of the "Performance Products Market Manager" there if you need it.

[McGuire]

There are a number of brands of these seal rings which fall into some basic types. You have your standard gas-filled seal ring, which is pressurized to several hundred psi at room temperature with no clamping force. When the clamping force is applied to flatten/squeeze the ring and the operating temperature increases, so does the pressure, expanding the seal into its receiver groove and perfecting the seal. Another type is vented to the pressure volume you are trying to seal via pinholes around the circumference of the ring (on the inside for an engine cylinder ring, of course, though there are outside sealing types for other applications). Another seal on a similar principle has an open, c-cross section to allow vessel pressure to expand the seal further. All these are designed with some memory to maintain the seal as the component (in this case a cylinder head) pulses up and down on the on the other component (block). These seals are often silver-plated to prevent brinneling.


A recent development on this theme is the Cometic Phuzion gasket system, which uses an MLS gasket body that retains the seal ring in position without the need for machining a receiver groove, and a gas-filled seal ring manufactured by Garlock. The gas-filled seal ring essentially takes the place of the stamped fire ring on a conventional fiber or composite gasket. Nearly bulletproof but at $400 a set they should be.

How do they get the gas inside that tiny ring? Via a reactive flux that is applied to the splice just before the assembly is welded together.

[J. Edlund]

http://www.tss.trell...ls_rings_gb.pdf

[cheapracer]

Paul for what its worth, my 2 best tricks with headgaskets are using a thin smear of silicon (like window glass sealer) on both sides of the gasket (let it dry preferably overnight) and using brand new head bolts. I never had a headgasket problem after I started doing this and not just my cars either.

[britishtrident]

I have more than a bit of experience using them on the 998cc wet Liner Imp engines

The Imp engine in even standard 875cc dry liner form was a serial head gasket blower for a whole collection of reasons some to do with the head & block design others to do with the layout of the cooling system.

The main problems with the engine itself centered around flexing of the head and block and and loss of clamping pressure through time due stress relaxation (aka low temperature creep ) in the aluminium head and block and the cylinder head gasket.

As already described the Wills ring is essentially very simple it is a tungsten tube filled with very high pressure inert gas formed into circle slightly larger than the engines bore size and butt welded at the ends.

Annular grooves for each cylinder are machined in the head to accommodate the Wills rings leaving approx 50% of the ring's cross section protruding above the head face. The Imp engine was an open deck design and was almost unique in that oil didn't drain back from the via passages in the head-block interface so all that was required to complete the water seal was a jointing paper gasket round the periphery of the head and small rubber nitrile rubber "O" ring (which was a pre-existing Imp engine design feature) to seal the oil feed to the camshaft.


The result was 99.99999999999% reliable, the seal would be maintained even in race conditions when the engines were being hammered at near 10,000 rpm.

When the cylinder head was removed the wills rings would appear very slightly flattened where they had made contact with the cylinder liner.

Normally we would leave the wills rings undisturbed in the head when the cylinder heads were removed for inspection and replace only the outer paper gasket and the rubber "O" ring when the cylinder head was refitted.

It was easy to check if a Wills ring was OK --- a slight tap with a magneto spanner or other small metal tool gave a distinctive sharp sound if the ring was still fully pressurised.

If a ring had to be removed a simple nick from the side with a small sharp chisel would deflate it and the ring would simply lift or fall out.

The head bolt tightening torque we used remained unchanged from that used for the standard Paynes lamminated aluminium gasket --- istr 35 lb ft