Restore exhaust manifolds?

[Jakes-66-K10]

I have a set of the 45 degree ram horns I'd like to use on my new crate engine. They are usable, but have some surface cracking on the driver side manifold. I am having them tanks and bead blasted today, but I need advice on what can be done to repair surface cracks and the best manifold paint. Seems everyone has mixed reviews on what lasts and what doesn't. Perhaps someone on here has first hand experience with this.

Thanks!

[chickenwing]

I bought some por-15 fireseal. Chickened out. Went with headers. There are lots of manifold paints out there. Last product I used was called castmagic. Looked great. I sold the car 4-6 months later. Still looked good up till then.

[Jakes-66-K10]

So you never put on the por15 stuff? That's one of the manifold repair kits I'm looking at...

[ndamerau]

I used the stainless steel manifold paint from Bill Hirsh. I have had it on for 3,000 miles and it still looks good. The only problem I have had with it is that the paint so closely matches the freshly blast cast iron that it is hard to tell if you have painted the entire manifold. I can e-mail a picture if you would like to see what it looks like, just PM your email address.

[Jakes-66-K10]

ndamerau I pm'd you. Thanks for your help, that is some input on paint but what about sealing surface cracks? Anybody had success with sealing manifolds?

[chickenwing]

Nope, never used it. Still sittin on my shelf.

[dave3156]

I took some manifolds to a metalizing coating company, they jet coated them. The process can also seal small cracks and the surface is permanent unlike paint. It was not cheap. It cost $120 for both manifolds. The surface looks like aluminium but is not shiney. Nothing (oil, paint, brake fluid, power steering fluid) sticks to them and they have drastically reduced the manifold heat tempature. They told me that when I had them done that the biggest application for the process was in high performance boat manifolds. I have pictures if you want to see what they look like.

[Terry Peerson]

Removing cracks is easy. Use a grinder. Once the crack is gone, there is no more crack. Surface cracks will continue to expand and grow until they go all the way through. Make sure you use a crack detector (magnaflux or x-ray the piece) to make sure it's gone. If the crack is completely through the manifold, there are two options; try welding the crack or throw the manifold away and get a new one (or get some headers) . I tried to have one welded for a '79 Cutlass (very rare exhaust manifold-only produced for two years and not available from GM). The guys that were working on it were EXPERT certified Code welders that weld for an industrial contractor (they really KNOW what they're doing). No matter what they did, they could not weld up the manifold. I ended up finding a used one at a junk yard two states away!

Good Luck!

T