As with any project, there's a right way and a wrong way to install headers. CHP talked to header manufacturers and visited Tom Dawson Racing Headers in Nuevo, California, to discover the right way.
Buy New and Know Your Car
The most important piece of advice is: Buy new. Header manufacturers have hundreds of part numbers to fit most applications and have carefully considered all the factors that go into making the equipment fit your car. Swap meet headers seem like a good idea, but you never know what you're going to get.
Chances are you'll be ordering headers by phone, so it's important to be prepared before you call. Make a list of all the components under the hood that might affect the placement of headers--power steering, A/C, and their related brackets can interfere with installation. Some manufacturers offer special A/C brackets or recommend modifying existing ones. Take a look at the cylinder heads and determine if they are straight- or angle-plug, aluminum or iron. If your car is a big-block model, find out if it's a factory installation by checking the numbers. A common problem with ill-fitting headers is a big-block installed on small-block motor mounts. According to Dawson, damaged or tired motor and transmission mounts can cause the engine to shift and interfere with header installation.
Know what transmission is in the vehicle and if it is two- or four-wheel drive. Vehicles that are '73 and later may require air pump-style headers to be 50-state legal. Not all Chevy headers are available with the air-injection manifold option, and not all air-injected headers are 50-state legal.
Another often overlooked factor for proper header selection is ride height. Low profile tires, lowered vehicles, and wheel size can change geometry and cause the header to hit the body. Unibody vehicles such as the first- and second-generation Camaros are sometimes bent out of shape from repeated abuse or just everyday wear and tear. When the front end is too far out of spec, a different part number is sometimes required to prevent the header collector flange from hitting the floorboard. Vehicle doors that are hard to open or close and fender spacing that is irregular or different on each side of the car are indications of frame distress. If the frame is bent, intermediate headers might solve this problem. If not, visit a frame shop for help.
Finally, measure the existing exhaust pipe to determine if a reducer is needed. The proper reducer will ensure that the collector will fit the existing exhaust.
Adding headers will put even more heat and stress on plug wires. You will be removing the spark plugs for this job anyway, so consider a new set of high-temp plug wires with the correct boot angle for the application. For tight-fit headers, use boots with a 90-degree angle; shorter spark plugs are also available that can move the plug wires out of harm's way.
The paint applied at the factory is intended to prevent rusting during shipping and storage and is not designed to last. For this reason, coatings are a good idea. They lower underhood temperatures, insulate the headers, and look better. If you're sure of your application, get the headers coated at the factory; it's less expensive and, in some cases, guaranteed. However, there is a drawback: Once the coating is applied, any torching, cutting, or dimpling of the exhaust will dull the finish and might void the warranty.
For the budget-minded, high-temp paint is an alternative. Use one full can on each header. After installation, start the car and heat them up. When they start to smoke, shut it off and let them cool and cure. Painting them yourself requires more maintenance than a professional coating, so be prepared to take the headers off and reapply the paint to keep them looking good.
Working on a hot rod takes time. Most guys we talked to mentioned the amount of time it takes to do the job right. Plan ahead for a weekend; stay home on a Friday night to start the project, and plan to take the car to the muffler shop for the final welds Saturday.
Go To Work
When the headers arrive, unpack the box and lay out all the components, making sure that the part number stamped on the header flange matches the number on the work order and that all the parts are included. Read the directions. There are specific instructions about modifying motor mounts, lifting the engine, and removing parts for easing installation.
Most headers are designed to be installed from the underside of the car without lifting the engine. A hoist is the best way to do this, but jackstands are more practical. Dawson and Hedman Headers both recommend raising the car a minimum of 36 inches--that's 3 feet--for standard long-tube headers.
Make sure that the battery is disconnected and the car is stable before disconnecting the factory exhaust from the heads. Slide under the car, remove the stock exhaust hangers, and move them out of the way. Guide the header, flange first, into the engine compartment. Go topside, install the front and rear bolts, and hang the gasket between the header and the head using the notches in the gasket. Then, find the bolt hole that looks impossible to access, and install it next. Once this is done the rest of the bolts should be easier.
For the paper gaskets, Dawson uses red high-temp silicone to prevent leakage; steel-core gaskets don't require silicone. If you're using paper gaskets, run a light bead on both sides of the gasket and let it set up well ahead of time. Don't tighten any bolts until all the bolts are threaded at least partially. Tighten the bolts evenly, from the inside to the outside, as tight as you can with a wrench--no cheater bars allowed and no air tools. Warm up the engine and go through the tightening process again. Do it again in a month or so; it requires constant maintenance. This will seal the header gasket to the head. For aluminum heads, use an anti-seize compound on the bolts.
Don’t Smash Your Headers
Denting, dimpling, and dinging are all colorful metaphors for smashing your headers. A simple tip: Don't do it. Header manufacturers have spent millions of dollars and years of research and development to produce a product that will fit. If your headers don't fit, call the tech line and talk it over before you hit anything with a hammer. Dawson's shop is full of headers that were carried in on stretchers after their owners thrashed them with heavy tools. If you close half of your primary pipe to make it fit, the purpose of the header is defeated. However, in the interest of objective, full-coverage journalism, CHP will hand out the advice on how to dimple your headers, only if it is used after all other avenues are exhausted.
The trick to a good dimple is making it smooth and radiused. Smaller dimples don't require heat as larger ones do, so start small. Use a round punch about 1 inch in diameter or larger. Roll it over the area to be dimpled while hitting it smartly with a hammer. Never hit the header directly with a hammer. For larger dimples, heat the area with a torch while rolling the punch. The downside to dimpling is that it creates hot spots and weak points in the tube. Heating the header with a torch cooks the carbon out of the steel and it begins to break down and disintegrate. The dimple will restrict flow and overheating a set of coated headers will dull the finish. Remember, many header manufacturers have the hit-'em-and-you-own-'em attitude. Please consider this before deciding to proceed. If it must be done, call the manufacturer to make sure the warranty will still be good after the job is completed.