On my last build I used nickle plated Red's headers on a 286 inch flathead. It was a mild build with an Isky 400jr cam and 2 97's. The car started right up on first try and ran well. I never gave it a second thought about "break in" time for the headers. They never turned colors and look as good today as they did when I installed them. I am thinking of going ceramic coating this time but it says to use other headers to break the engine in before installing the ceramic coating. Has anyone actually done this ? I am wonderng if stainless might be a better choice.
The only thing I was told was to drive sedately for a day so as to not put too much heat into them initially. Did that and after 10 years they were still good and that was on an every day driver. The ones on my avatar didn't get the same sedate driving and they went off after a while.
I had my headers ceramic coated and the direction I was given was to have the timing set as well as the Air/fuel ratios correct before I installed them. I had no issues with mine.
Cad flathead exhaust manifolds were porcelainized. Our local muffler shop sold a few sets of flathead ford Fentons that were porcelain coated here in town.
When you are breaking in a fresh mill you keep the revs up until the cam beaks in. When an engine is revving stationary with no load the headers get pretty hot, I have actually seen them glowing red on a more modern big block car. I got an idea that the abnormal heat is not good for the ceramic coating. I know on painted headers when they are fresh we like to warm 'em and let 'em cool a few times before we get after it. The paint is less likely to flake off if it gets cured well first. Anyway just my thoughts on it.
That is a CYA from the MFGR. A too lean condition will torch the ceramic right off the header. I used to sell dozens of set of coated headers from PARR. That is the only thing they would not warranty
None of my ceramic coated headers have ever discolored or had any finish issues........in over 30 years......with lots of miles on them.......