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65nss4spdGTO · 01-09-2013, 01:12 AM

Lots of good comments in the last boosted cylinder head thread.

What happens when the head lifts and creates leakage? How much movement are we looking at with a Pontiac head?

We lost seal on a sleeve once, filled the cylinder with water and puked it out between the head and block.

Calvin Hill
Hill Performance
708-250-7420

Tom Vaught · 01-09-2013, 05:54 PM

Most Boost Gasket Engineers I have talked to over the years assume that the head will lift approximately .007"-.010" and design into their MLS gaskets enough room to seal at .012". Some of this info is for a diesel engine at high boost levels that the average boosted engine would not experience.

Even if you install a Gas ring like a diesel uses, if the ring diameter is too small, say .060" tube diameter, then the ring when ovalized with head torque will only have .007 to .010" to "follow the head". Once the ovalized state is converted to a round shape that .001" more movement = .001" leakage.

Diesel engines have now gone to a .093" tube diameter and have .015" to .020" ovalization of the ring. This allows the head to move over .010" upward and the head will still stay sealed.

Copper gaskets and wire rings have no ovalization of the wire. They use the concept that a Labyrinth created by the wire imbedding into the copper will impede the gas leakage enough to basically seal the head under most conditions in racing for a period of time.

You might have more leakage on a low boost system with a copper gasket/wire vs a higher boost situation because the leakage rate will be the same for both cases but the high boost system will see more sealing effect because the leakage ratio will be much less with the high boost engine.

We have used NO GASKETS and the Diesel Gas Ring technology for years on our Single Cylinder Engine Testing.

Tom Vaught

Travis Q · 01-09-2013, 08:01 PM

There's two schools of thought that I have encountered when it comes to the subject of cylinder head lifting.

Both approaches are just as valid as the other.

One is to allow the head to lift, and choose a sealing mechanism that will cope with the clearance created between the head and the block when the head lifts.

Whe the head lifts, it usually "bows" in between the studs, and the point of maximum lift/deflection occurs at the midpoint between the head fasteners. So some people oring the head and reciever groove the block/liner and use a copper gasket. This works well to a point. Some use a standard gasket and machine a large, squared groove into the deck of both the block and the head, and fit a closely machined ring of copper into the groove. The ring is a rectangular cross section, and fits deeply into the block and the head. The standrad gasket is cut out to fit around these rings, and is used to seal water only. This method works great, but is difficult to machine and, from what I hear, is nearly impossible to disassemble once the engine has seen some high boost cycles. Another method is the one Marty used and he touched on it in the other thread, and that's the gas filled oring/sealing ring. The ring is compressed slightly in its groove as the head is torqued, and if the head lifts the ring expands to take up the gap. Also, as the hot combusion gases come into contact with the ring, the pressure in the ring increases, which tightens the seal further. This is a great method to use if you have room between the cylinders for the rings, which most engnes do, but some don't.

The other train of thought is to do everything humanly possible to keep the head from lifting to begin with. This usually entails a billet cylinder head, large head studs in greater than factory numbers, or cylinder head braces, in the case of some factory aluminum castings used for racing. Tractor pullers have some rather ingenious methods of keeping everything sealed up, but to keep from getting death threats, I won't post those here. They are far to heavy for our uses in drag racing, anyway, and involve quite a bit of tricky machine work to the block and head.

That's what little I know on the subject. I know that Rodney and I have found the sweet spot for keeping our E-heads sealed up, and that has greatly minimized our head lifting/gasket sealing issues. With alcohol for fuel, if you lift the head much at all, you torch the head and block, no exceptions. So it's pretty imperative to keep them down!

TQ

rodneybutler · 01-09-2013, 08:33 PM

Tom. I have lifted the heads on the dyno with a pump gas, 8-71 roots deal when I surpassed the timing threshold trying to make power. I actually saw the compression blow out. It had Cometic head gaskets on it and I figured they were done after that. Did leak down, all good. Backed two degrees out of it and finished the dyno tuning with no problems. No water leaking, no compression loss. I was pretty impressed that they stayed sealed up after I abused them so much! Was running 14 psi with BDS trying to make 900hp. Needless to say, I'm not impressed with that blower. That engine would make 750 NA pump gas.

beastmaster · 01-09-2013, 08:59 PM

" Travis Q " Another method is the one Marty used and he touched on it in the other thread, and that's the gas filled oring/sealing ring. The ring is compressed slightly in its groove as the head is torqued, and if the head lifts the ring expands to take up the gap. Also, as the hot combusion gases come into contact with the ring, the pressure in the ring increases, which tightens the seal further. This is a great method to use if you have room between the cylinders for the rings, which most engnes do, but some don't.

That method is the commonly used in the building of the hot section in a turbine engine . We call them the e-ring . Good ideal!

taff2 · 01-09-2013, 10:34 PM

Years back when I used to run a 2.0 litre turbo Ford Cosworth, basically a 24 valve Cosworth head on an uprated Pinto bottom end, it was common to machine a groove in just the block and use a steel O ring wire with a standard composite gasket. This was usually well up to containing 30+ psi of boost. And they only have 10 bolts holding the head down.

Marty Palbykin · 01-09-2013, 10:57 PM

Quote:

Originally Posted by Travis Q

There's two schools of thought that I have encountered when it comes to the subject of cylinder head lifting.

Both approaches are just as valid as the other.

One is to allow the head to lift, and choose a sealing mechanism that will cope with the clearance created between the head and the block when the head lifts.

Whe the head lifts, it usually "bows" in between the studs, and the point of maximum lift/deflection occurs at the midpoint between the head fasteners. So some people oring the head and reciever groove the block/liner and use a copper gasket. This works well to a point. Some use a standard gasket and machine a large, squared groove into the deck of both the block and the head, and fit a closely machined ring of copper into the groove. The ring is a rectangular cross section, and fits deeply into the block and the head. The standrad gasket is cut out to fit around these rings, and is used to seal water only. This method works great, but is difficult to machine and, from what I hear, is nearly impossible to disassemble once the engine has seen some high boost cycles. Another method is the one Marty used and he touched on it in the other thread, and that's the gas filled oring/sealing ring. The ring is compressed slightly in its groove as the head is torqued, and if the head lifts the ring expands to take up the gap. Also, as the hot combusion gases come into contact with the ring, the pressure in the ring increases, which tightens the seal further. This is a great method to use if you have room between the cylinders for the rings, which most engnes do, but some don't.

The other train of thought is to do everything humanly possible to keep the head from lifting to begin with. This usually entails a billet cylinder head, large head studs in greater than factory numbers, or cylinder head braces, in the case of some factory aluminum castings used for racing. Tractor pullers have some rather ingenious methods of keeping everything sealed up, but to keep from getting death threats, I won't post those here. They are far to heavy for our uses in drag racing, anyway, and involve quite a bit of tricky machine work to the block and head.

That's what little I know on the subject. I know that Rodney and I have found the sweet spot for keeping our E-heads sealed up, and that has greatly minimized our head lifting/gasket sealing issues. With alcohol for fuel, if you lift the head much at all, you torch the head and block, no exceptions. So it's pretty imperative to keep them down!

TQ

Travis, you got it. The ring I use is like a spring if you lift the heads a little it will stay sealed. Never had one fail. If the head bolts give up well thats not going to work. But the design is the higher the cylinder pressure the hardered it seals because it is exposed to cylinder pressure. It really is bullit proof.

Marty Palbykin · 01-09-2013, 11:01 PM

Quote:

Originally Posted by beastmaster

" Travis Q " Another method is the one Marty used and he touched on it in the other thread, and that's the gas filled oring/sealing ring. The ring is compressed slightly in its groove as the head is torqued, and if the head lifts the ring expands to take up the gap. Also, as the hot combusion gases come into contact with the ring, the pressure in the ring increases, which tightens the seal further. This is a great method to use if you have room between the cylinders for the rings, which most engnes do, but some don't.

That method is the commonly used in the building of the hot section in a turbine engine . We call them the e-ring . Good ideal!

It definatly is not a gas filled ring.
As soon a we got the tuneup right the gas filled ring failed.
But the solid ring did not.
Machining is also very simple.