# Intake manifold burnt paint GTO 1966



## praga (Oct 17, 2021)

Engine after total rebuild, fresh repaint, first 200 miles on the road, second long ride only.
Carter AFB 4-barrel carburetor on intake manifold, Air Injection Reactor (AIR).
I have noticed that the paint on the intake manifold is strongly burnt.
I am not sure if this is a normal thing or if it is an some kind of problem.
Should I stop the Break-in process?


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## PontiacJim (Dec 29, 2012)

praga said:


> Engine after total rebuild, fresh repaint, first 200 miles on the road, second long ride only.
> Carter AFB 4-barrel carburetor on intake manifold, Air Injection Reactor (AIR).
> I have noticed that the paint on the intake manifold is strongly burnt.
> I am not sure if this is a normal thing or if it is an some kind of problem.
> ...



Normal. There are hot exhaust gases passing through there, so it gets hot. It is important on how the manifold was prepped, ie sand blasted, and the brand of paint used.

Others here will chime in, but there is a means to minimize the burning of the paint so it won't burn off, but may get discolored.

However, things to check:

The stock exhaust manifolds use a "butterfly valve" on the passenger side that is bi-metal spring loaded. If you are still using this, make sure it is operating and not closed or partially shut down as this can put more heat through the exhaust crossover and your engine will run a little for the worse.

Timing - if the timing is retarded too much, it will cause the engine to run hot, hotter than it needs to. Many things can cause retarded timing from wrong Initial timing at the balancer to distributor issues. Other factors can play into this, but timing is usually the issue.

Carb - Running too lean. An engine that runs lean will generate more cylinder heat. If upgrading the engine with go fast goodies like bigger cam, higher flowing CFM heads, headers, etc., can require more fuel. The stock Carter AFB flows about 550CFM's which can be fine for a stock engine, but might not cut it if you start changing to those items to make more HP/TQ.


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## praga (Oct 17, 2021)

PontiacJim said:


> Normal. There are hot exhaust gases passing through there, so it gets hot. It is important on how the manifold was prepped, ie sand blasted, and the brand of paint used.
> 
> Others here will chime in, but there is a means to minimize the burning of the paint so it won't burn off, but may get discolored.
> 
> ...


Thank you for the very detailed answer and possible research directions.

Carb - during the braking process we set mixture a little richer. After 1,000 miles, we'll adjust to normal. I hope there's no problem here, I'll check.

Timing - I have to check in detail, AIR needs specific ignition timing setting, I'll focus on that.

Butterfly valve - this is the first I've heard of it, I'll have to see if there's a bimetal and check the functionality.

it'll take me some time, I'll get back to you with the result.
Thank you very much for your help


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## MidnightAuto (May 28, 2018)

As Jim says totally normal. Annoyingly so if u are trying to keep clean look.


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## Jetzster (Jan 18, 2020)

Sometimes priming with rattle-can 1200° Black primer first helps with stopping the peeling some but it’s still gonna turn brown , just the way it is😕


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## Baaad65 (Aug 29, 2019)

Yup, if you don't want to block it off treat it like an exhaust manifold, sandblasted my manifolds then used KBS extreme primer and paint then baked them on the grill and they still look great but they're cast iron colored, used the same primer but engine paint on the block and it's discolored especially by the siamese center exhaust ports. Doubt if you want to remove the intake and repaint it but maybe you can work on that spot taking the paint off and priming it with header primer and 500° engine paint...just a suggestion.


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## Gremlin66 (Oct 11, 2009)

My intake manifold gasket set had the block off gaskets for the exhaust crossover which i did install. Havent put any miles on it to speak of since its nearly ready for paint. It might just take a little longer to warm up with the crossover blanked but so be it.


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