Sound From Headers
 

I talked my friend into getting a set of flowtech shorty headers for his 93 stang. He ended up picking up a set of their ceramic coated model. They look great on the car, runs and sounds a lot better. Only one problem when he goes into wide open throttle it makes a knocking noise. Sounds just like if you take a steel object a hit the exhaust. Only happens at wot. We have already checked the engine compartment to see if something is hitting againts it there is nothing on or around the header. What could this be???

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67'fastback- Edelbrock carb, intake, cam, valve springs. Road lifters, Comp Cam rocker arms, windage tray, cerama coated headers, dual flows with H-pipe, modded c-4, tci stall converter, perma cool electric fan, aluminum water pump, griffen aluminum radiator, accel 8.8 cable, wide cap distriburator, magnetic pick up, manley valves, v-matic hurst shifter, edelbrock performer nitrous, carter electric fuel pump, ignitor coil, solid motor mounts, magna racing suspension, poly urathane bushings, und

Could be a header gasket leak.. or possibly a leak at the header/H-Pipe coupling. Try and isolate the noise by listening through a tube. I hope this helps.

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MAC equal length headers, MAC Off-Road H-Pipe, Flowmaster mufflers, 373's, March ram-air kit, underdrive pulleys, 73mm MAF, 75mm TB, Saleen Intake (ported), Edelbrock 6037 heads (ported, polished, 3 angle valve-job 255CFM @.500), 1.6 FMS RR's, Wolverine 1087 Cam, 24lb injectors, MSD 6AL, Subframe connectors, Griggs Adustable Lower Control Arms, Lakewood 50/50 shocks, SSM Upper Control Arms... and probably some more in there I forgot

The noise only happens when the car is under load (ex. Moving at WOT)

That's weird becuase i have those same headers (mine aren't coated) and they don't make that noise. It could be an internal engine noise (worst case scenario). Good luck

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'84 Mustang 5.0 T5, FMS aluminum radiator & 180* thermostat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, smog pump idler, now with hi-po collapsed lifters in #3 or #4 :)

Detonation? Did it ever doit before?

Rev

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'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.