Has anyone ceramic coated their heater boxes? I have the tins off and repaired. Heat paint or ceramic coated inside and out? I am concerned about if there is any toxic fumes given off into the cabin. Also if I coat the inside of the header will it reduce the heat transfer?
Thanks Brian

I had mine coated at Jet Hot coatings, and it's worked out great with no observable downside. Nevertheless, I always run with a carbon monoxide detector in the car as these are now 35 years old. Even the SSI exchangers have been known to crack from age.

I di my 911 SC some years ago. never had any odors in the cabin, they were coated externally only

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Coating the inside will make them less efficient. You don't want to slow down heat transfer.

According to a Jet Hot Dealer, coating reduces exterior temperature by 30%. A /6 rear trunk gets really hot so besides the protective coating for external rust, your Hershey Bar in the trunk won't melt.

But the rear trunk makes a great place to keep a take out pizza warm!