Take a look at these pics of my headers. These have been on the 408 motor since '04 but turned color and even peeled on cylinders 1&3 after I installed the NX279HR cam. I contacted Hedman regarding the 5 year warranty on the coating - we are still back and forth on that. But what doesn't make sense is, cylinders 1,3 and 6,8 show a lot of discoloration which Hedman says is most likely due to poor fuel distribution. I would have suspected a hot condition if the carb was too lean, but I don't think that was the case. Also, if this were from one side of the carb, it would show up as cylinders 1,7,4,6 and 3,5,2,8 (think that's how they are paired).

Particulars - intake was Ede Perf 2-0. Motor saw 2 carbs, For most of '04 the motor had a 770 Avenger on it. For most of '05 it had a 670 Avenger on it - both were box stock jetting. Cam was the Comp NX279HR, 230/242 113LSA installed at 108ICL. Oil looked good, no heavy gas smell in the motor. I chalked up the carbon buildup just to a lot of low RPM/idle running time from moving the car in/out of the garage. I have to wonder if the early exhaust timing was blowing down the cylinder far too early with the short stroke motor and the wide LSA, possible while the fuel mixture was still unburnt. I had previously stated that the motor had an incredible exhaust sound when I installed the new cam.

Any thoughts?

I have seen headers look like that twice. Once was because it was too retarded and almost firing into the headers. The other was that somebody tired to break in a cam with the headers on and had poor air flow. I've never seen only certain tubes discolor though. I wouldn't think it was mechanical because it would be the same on all cylinders. Poor fuel distribution maybe, but it's not like these manifolds haven't been around forever.