We recommend breaking in a new engine using factory manifolds or an old set of headers. This is to prevent engines that are not optimally tuned from damaging the thermal coating on your new headers.
Untuned or Improperly Tuned Engines Will Destroy Headers!
This applies to engines that are running either too lean OR too rich. Either condition creates excessive heat, which breaks down the coating materials and the header welds. Sources of excess heat problems include:
- Lack of adequate intake air
- Incorrect timing
- Improper adjustment of the carburetor or fuel injection
- Clogged or restricted exhaust
- Vacuum leaks.
Small air cleaners on high power street rods are one common cause of high exhaust temperatures. Even a single 650cfm carburetor consumes a small roomful of air every minute, so restricting the size of the intake point is a big mistake. Those massive air scoops on competition cars exist for a reason. Increasing the size of the exhaust system without increasing the amount of air flow simply chokes the engine, and causes it to run too rich and too hot.
Timing and fuel system adjustments are another important consideration. A perfectly tuned motor is operating at maximum efficiency--turning fuel into power. An improperly tuned motor is converting fuel into excess heat. The absolute best way to know if you're engine is running properly is to use an exhaust gas analyzer. The "shade tree" method is to use a timing light, and read the color of the spark plugs and inside of the exhaust pipe. Both should be a light tan color. Black indicates a too rich condition, and white indicates a too lean condition.
Vacuum leaks are another common source of timing and fuel mixture problems. While it can time consuming to chase vacuum problems, it's worth the effort. An engine that is running right is less costly to operate, more fun to drive, and will last longer than one that is not. If you're not sure what to do to correct a timing or fuel problem, it is worth paying a professional to sort it out!