Filling rust pits in a manifold?

[Dwight Romberger]

Hi All,

What can I use to fill the rust pits in my cast iron intake and exhaust manifolds? I have had them media blasted, and I plan to paint them with a high temp paint cast iron color paint from Hirsh.

Thanks for the help.

Dwight

[Barney Eaton]

This may be crazy and I am no expert, but what about lead or solder. Once blasted they will have a nice clean surface for solder to stick and I'm thinking 60/40 solder melts around 400 degrees, hopefully it would not remelt.

[nickelroadster]

I am not aware of any high temp filler, especially on the exhaust manifolds. You might try one of the various products that they make to repair mufflers with that you can find at your local auto parts store. These products don't work very well for that but you may be able to find that they may fill somepits ok. Brazing them might also work. Solder might work on the intake but the exhaust would be too hot.

[michaelod]

Dwight,

High temp paint will not hold up as exhaust manifolds generally run between 500f and 1000f degrees. There are some coatings such as JET-HOT that will retain their color over time pretty well.

Thanks,

[Mark Shaw]

Ceramic coating would be an option to explore...

[Bob Engle]

You can grind and sand the surfaces to remove minor pitting. After grinding, sandblast the surface with very coarse sand to get a a cast appearance back on the manifolds. I then soak the castings in Muriatic acid to thoroughly clean the surfaces. I finished my cast exhaust parts with VHT paint and baked it to get the correct cure. Remember, original castings had many pits and oclusions and flash due to the sand cast process; so perfection isn't needed to get to original condition.

Good Porcelain coatings can build up and fill pits. It is an expensive operation to get it done right. They tend to look artifical with the smooth shiney finish.

Bob

[Bhigdog]

There are some high temp fillers that would probably work on the intake. The exhaust is tougher. Don't bother with the POR 15 restoration kit. Didn't work for me, although they did give me my money back. Filling the pits with braze then filing smooth would work for the areas you could get at but would be a Herculean task. Any coating will telegraph the pits. Rust and pits are generally accepted as just being the nature of the beast.................Bob

[Mark Shaw]

My earlier post suggested ceramic coatings. Coincidentally, our local BCA chapter had a short presentation on this at our meeting on Sunday afternoon. I learned that ceramic coatings significantly reduce engine compartment temperature and are available in several finishes to mimic original grey iron. It eliminates rust potential and will not come off or discolor.

[Dwight Romberger]

Thanks everyone for your input on this question. I am going to look into ceramic coating. If it's affordable for me, I think I will try it. If not I will go with the baked cured VHT cast iron color paint. I think I'll leave the pits as they are.

I'll show pics when they are done.

Thanks again,

Dwight

[Fred Rawling]

Dwight,

I think you made a good decission. Welding and grinding on an already fragil and hard to replace exhaust manifold is not in my opinion a good idea.

[Dwight Romberger]

Fred,

Thanks for the advice.

Dwight