Harry Truman once said, If you cant take the heat, stay out of the kitchen. He could have been talking about either thin-skinned politicians or header gaskets. Its hard to imagine a component that is heat stressed more than a header gasket. Exhaust-gas temperatures in excess of 1,300- to 1,500-degrees F are not uncommon, yet the gasket is required to withstand this heat blast several times a day for years. Is it any wonder that header gaskets blow out occasionally?
On the other hand, there are few things more aggravating than that ticking sound that gradually builds into a full-fledged leak, making your otherwise pristine Pro Touring Camaro sound more like a cantankerous Stanley Steamer. You could have all the trick parts in the world bolted to that Camaro, but with an exhaust leak, it has no more boulevard appeal than a ¼-million-mile 74 Vega with two dead cylinders.
The best defense against those infuriating exhaust leaks is a great offense starting with quality gaskets. Like most things in life, you get what you pay for and those paper gaskets that come with most header sets are good for a month or two of operation before they surrender to heat and exhaust gas pressure. But those gaskets are not your only choice now that theres a whole slew of slick header and collector gaskets. The latest versions are the aluminum and copper gaskets that are soft enough to conform to the header flange yet durable enough not to melt under that daily hot exhaust assault. But theres more to this story than just new materials. There are several techniques and tricks you can employ to ensure that the header bolts stay tight, and the gaskets keep their place.
The biggest challenge to sealing headers and collectors is keeping the gasket tight against the head. The most common problem with blown header gaskets isnt the gasket itself, but the fact that the bolt loses its torque. While it may seem that the bolt loosens because of some occult combination of heat cycling and vibration, the truth is that the gasket compresses and this reduction in thickness causes the bolt to become loose.
This is a common problem with the conventional compressed-fiber-material gaskets. After the gasket is tightened and subjected to several heat cycles, the material compresses. This reduces the distance between the header flange and the head, which creates the same effect as loosening the bolts. Once bolt torque is lost, exhaust-gas pressure can push past the gasket. In a relatively short time, the hot exhaust gas can burn the gasket, creating the exhaust leak. Several years ago, numerous companies began making high-performance gaskets that were less compressible. The most common design is the wire- reinforced graphite-compound gasket made famous by Fel-Pro. These gaskets compress less than fiber-style gaskets due to their internal wire reinforcement, but its still a good idea to recheck bolt torque at least once. The graphite coating also prevents sticking and allows the gasket to move when the header heats up and expands.
The latest generation of gaskets are the copper or aluminum-frame gaskets. The aluminum gaskets rely on an internal graphite seal to prevent leakage. These seals can be replaced if they leak or become damaged so you dont have to buy the frame in addition to the seals. There are several copper gaskets with SCE as the originator of the embossed copper header gasket that is designed to create a leakproof seal when the header is tightened down. There is a slight amount of crush built into the embossed area, and the ridge creates an increased clamping load without requiring increased bolt torque. Copper also does not suffer from the movement problems that can plague other gaskets. Even with all these advantages, its still a good idea to retorque any gasket after one or two heat cycles to ensure a solid, long-lasting seal.
As you can see, theres much more to header and collector gaskets than just pulling them out of the package and bolting them on. There are plenty of different styles and prices to choose from. But regardless of which you choose, a little maintenance is required to make these gaskets live longer.