You’ve got questions. We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re examining why new headers can cause strange noises from your engine.
Q: I have a 1990 Camaro that is well taken care of. I recently added a set of headers, and I’ve been hearing funny sounds from underneath the car ever since.
I went back to the shop that installed the headers and they determined that the headers were not leaking. A friend of mine thought maybe the engine was experiencing detonation and suggested I swap out the Hypertech chip for the stop chip. I still have the problem! The only other modification I made to the car is a Flowmaster muffler. I am using 92-octane gasoline. The headers, muffler, and chip are all CARB legal. Any ideas?
A: The noise you are hearing is likely the normal “ringing” sound a healthy engine with headers makes. This is due to the energy of the exhaust wave pulse hitting the header tube, causing it to vibrate. You may hear that noise as an engine ping. You won’t hear that sound with stock exhaust manifolds. Due to their extra mass, manifolds vibrate at a much lower frequency and absorb much of the exhaust gas energy.
Still, engine detonation is a serious problem and can result in severe engine damage. Detonation is the result of our air/fuel mixture being burned too rapidly around Top Dead Center, when the leverage ratio between the connecting rods and crankshaft is poor. That rapid air/fuel burn creates excessive cylinder pressure, which in turn makes shock waves that can damage or destroy an engine.
The bottom line is if detonation is occurring, your compression ratio is too high for the fuel you are using. That doesn’t seem likely in your case, but a quick way to find out is to add some octane booster to your gas and see if the noise goes away. If it doesn’t, you need to lower the compression ratio.