C-rings, O-rings, and Copper Gaskets
Ken's in-a-nutshell explination of Copper head gaskets and o-rings, C-rings, and Fire rings (3 commonly confused methods of holding compression in)
Copper head gaskets and O-rings -
- A solid copper head gasket is used in place of a standard head gasket. Since the copper does not crush, and is so stiff, grooves are machined into the block and stainless steel wire "o-rings" are placed in the grooves. When the head is torqued down, these o-rings protrude into the copper, effectively sealing it. In high boost applications, a "reciever" groove may be added to the heads directly above the o-rings. The copper gasket will then crush up into the groove, providing better sealing.
The wire o-rings must be used with copper gaskets, and studs must be used or they won't seal. The o-rings are only used with copper gaskets.
The benefits of copper gaskets/o-rings is that when installed properly, it is an indestructable combination. (some of the pulling engines we build see well over 200psi of boost) It is also inexpensive.
The downside is that they are a pain in the **** to get to seal right the 1st time. (we've even had a set up here that didn't seal up and we had to pull the engine and do it over) The reason is that since the copper gaskets don't crush, any imperfections in the o-rings/block will leak after they are installed. There are special instructions/methods for getting the gaskets to seal correctly.
C-rings -
- A C-ring is basically a 2 piece ring that sits outside of the cylinder. The inside of the ring is shaped like a "C", hence the name. Since the C-ring is a 2 piece ring, when compression is put against it, it tries to expand. The more force you put on it, the more it tries to expand and the better it seals.
Maching of the block is required. In extreme (200+psi) applications, maching of the heads helps, but in normal cases it isn't necessary. A groove gets machined into the block around each cylinder the c-ring gets placed in the groove. A special head gasket is required that fits around the c-ring.
The benefits of c-rings are that they're not that hard to do, and they seal up correctly the 1st time (studs are required). They are also as tough as the copper head gaskets and we have used them in high boost applications without problems. The c-rings are also very forgiving. The head can lift slightly and the rings will expand to compensate.
The downside is the cost (upwards of $1200 for the kit).
Fire rings - (commonly confused with C-rings)
- A Fire Ring is basically a jumbo-sized o-ring. A groove is machined into the block, and a reciever groove must be machined into the head. When the head is torqued down, the ring gets compressed and crushed into the grooves, sealing the combustion.
A stock head gasket can be cut to fit around the fire ring and used. Studs are required. The grooves must be directly across from each other, or the show's over. To accomplish this, you either need access to a CNC machine, or you need to buy the reference plate and tools necessary to cut the grooves correctly.
The upside is that fire rings are also easy to get to seal. They will hold enough boost for most applications.
The downside is that they aren't as tough as coppers or c-rings, and the cost is up there as well - probably close to $1000 for the kit.
Ken