TedH

I tried leaning out the idle mixture on the carb and probably should have heeded the warnings of Jet-Hot regarding getting too lean. I didn't see any improvement in the vacuum so I backed them back out to '6 turns out from seated' as Lars had sent to me (should have trusted your judgement Lars). Anyway, I took the vette out for a cruise and stopped over at my gear-head brother-in-law's house, popped the hood and voila! ceramic coating 'ripped' across the top portion of the #7 header pipe. Brother-in-law was convinced it was foreigh material on the header pipe; he was partly right, it was the Jet-Hot Coating! After the car sat overnight, I examined the coating on the headers and it appears to be limited to this 1" square area of the #7 pipe. I had turned the mixture screws down to about '4.5 turns out' on Sunday and when there was no noticable idle/vac improvement I tried for some more... Needless to say, I saw the error of my ways too late (actually much later as there was no visible damage for several hours). Once I had turned the car off and reset to Lars' setting I suspect that I had already super-heated the header tubes to in excess of 1300 degrees (Jet-Hot's limit for warranty) by leaning the idle out too far on the left cylinder head.

I'm hoping that the peeling won't spread. If it gets too bad, I can ship it back for a re-coat of that header. I'd rather not for obvious reasons ($).

Another lesson learned. Not dealing with cast iron exhaust manifolds anymore...

Budman68

I have the same problem on one pipe. I called Jet-Hot and it is under warranty, but you still have to pull it. My bad spot seems to have blended in and has not rusted. I think they are double coated and there is another layer of some product under the satin coating.

TedH

I suspect the defect may be something they had a problem with when they coated these headers. There was a quality control (QC) problem with the 'left header' as they referred to it and I suspect this is the suspect area (everywhere else, the headers are fine). I may not have gone as lean as I thought but that was my first guess. I'll give them a call on Tuesday and see about the re-coat. The coating kind of 'accordioned' where it peeled and appears to be very symmetrical (almost like they put a 'patch' on the header in this spot to correct whatever defect was caught by QC. I have the original box the headers came in so I'd have the cost of the postage to send it back to them (I hope they are good for that postage). It's not that hard to pull the driver's header; just have to get it up on jackstands and pull it out the underside of the engine compartment.

Will advise what I hear from them on Tuesday.


[Modified by TedH, 4:36 PM 5/27/2002]

SteveG75

I had the same problem on my Dunomax Cerama-Coat headers but it was #8 instead of #7. I also believe they are coated by Jet Coat.

Call me Bubba, but I got some Duplicolor Hi Temp Ceramic paint (rated at 1200 degrees) in Aluminum and just touched up that area. Looks pretty good and I have had no problems in the last 1000+ miles.