So we agree, inside coating is limited coverage and most positives are in the beginning of the header?
I believe it's safe to assume that area has the highest temps in a typical header, how do we fairly judge its longevity and therefore its benefits?
Haven't heard anybody mention any concerns on the inside of used coated headers.

TTI has offered the interior ceramic coating as on option for a long time. I have never seen anyone talk about it either as far as failures or successes. Soot/film may build up on the inside enough that it can't rust or peel off like it does on the outside. Or the interior coating does eventually fail like it does on the outside, but the soot covers it up and nobody has really looked under it to find out.

If I had a new set with no coating inside I would not hesitate to flood the openings on both ends as far as I could get at with VHT header paint. Better than nothing at all.

Again, according to CCP; if the coating changes color and texture nearer to the exhaust port, it is usually due to a lean condition. If the change of color and texture is further down the tube, it is usually due to an overly rich condition because the excess fuel is burning down there.

You could try Eastwood's Internal Exhaust Coating - it comes with a long nozzle and gets good reviews:

https://www.eastwood.com/eastwood-hi-temp-internal-exhaust-coating-w-nozzle.html

I have wondered about this product. Obviously this is meant for unused headers because how can a used header be cleaned sufficiently internally for proper adhesion?

Does it require or benefit from any post treatment oven cure/bake?

i guess i'll find out, as i ordered a couple of cans of that stuff. [as well as several other items that were on sale, so i ended up with free shipping, as well as $15.00 off my order]
wouldn't be the first time i threw money away on stuff that didn't work.
i have a set of TTI step headers someone trashed the primary pipes trying to get them to fit straight plug heads.
i'm almost done repairing the one side, and i plan on blasting them good from both ends having it done with an industrial blaster using a flexible hose down each tube.
good thing i got these pipes super cheap.

Could likely clean the inside of a dirty used set by using pipe cleaner brushes combined with spraying down each tube with an aerosol solvent. Exhaust soot can be pretty stubborn so just solvent without the brushes may not accomplish much. I imagine it would be a dirty job as well.

Make sure whatever solvent is used does not leave a residue behind. Acetone followed by alcohol usually works well. Certain brand a of brake clean can as well but some do leave a residual film

hi
had my USED headers jet hot coated , inside and out , 8 years and still look good .

also much lower engine compartment temps !

Would a small chimney sweep brush work?

I would also think any header with lots of run time with leaded race gas would be generating a lot of toxic lead in the residues and airborne if using any brushes.

I've been at this game for 50+ years the last 25 owning and operating a classic car repair / resto business. my local machinist was quite curious at to what coating was on the headers of a BB old's he had just Dynoed. I asked why the curiosity? he said he had never seen set of coated headers maintain their coating after a break in and x number of dyno pulls. I answered Jet Hot

Lots of positive posts regarding JetHot coatings. Obviously, they should seriously be considered.

Any similar love for CCP?

I haven't sent the new TTIs off to a coater yet. As I have said; I have been leaning towards CCP largely because they have participated here and took the time to discuss my order with me.

I would welcome any and all experiences with either coater as I make this decision.

Has anyone ordered the TTI headers with the nickel plating? I had a contract gig with a company that made tools for most of the companies except for Snap-On, and they plating everything with a nickel-chrome solution. They did that before roll die forming the brand and part numbers into the sockets.

Again, under hood heat would be the biggest disadvantage.

Understand typical "chrome" plating is effectively nearly clear, very shiny, and somewhat durable Chromium plating over very reflective base plate of nickel. I doubt that process undermines the nickel plating but more enhances its durability, which is not high anyway in limited external air flow settings as an exhaust coating IMO.

Sorry no experience a CCP I will comment that I believe Jet Hot was the original company that started the coating idea on exhaust components. I seem to remember reading two guys were working for a company that was doing coatings for NASA. They decided to apply the coating to a few headers and the company evolved form doing so. This was 30? + years ago ? There have been a lot of wanna be's that take the $$ but fall way short when the pedal hits the metal. Again not saying CCP isn't a s good but I have ZERO experience with them. Being in a business, I had to cover my backside so I encouraged JH. The few customers that chose others for monetary reasons found out why the others were cheaper