Exhaust Manifold Pitting

[Guest philipswanson]

I bought a fairly rare Chevy 396 L/H exhaust manifold for my 68 El Camino but it has some pretty deep outside pitting. Does anyone have any experience in grinding or filling pits in cast iron? The manifold seems to have plenty of wall thickness but cast iron is tough stuff and I want to make it look close to natural. I plan to coat both of them after grinding the left one if I can find a thicker porcelin coating to hide the irregularities. Anyone deal with this before with any success?

Thanks, Phil Swanson

:confused::confused::confused:

[Larry Schramm]

Look here for the complete discussion

http://forums.aaca.org/f165/filling-rust-pits-manifold-275867.html

[Guest philipswanson]

Larry,

I had read that thread before but it didn't really say much. The guy that started the thread just states that he is going to live with the pits. I can't because they are fairly deep. I am looking for someone that suceeded not someone that just left the pits stay. The only informative post there was the guy that said you could grind them and finish with a coarse sandblast. That's what I am trying to get more information on. That process.

Thanks, Phil

[Larry Schramm]

If you look at Mark Shaws post I believe that he talks about porcelain coating till the pits are filled after sand blasting. You might send him a note and see if he can forward you some additional information. Good luck

[johnworden1]

Phil, If the pits are deep, grinding to eliminate them will change the contour of the piece which I assume you realize. Cast iron blocks can be welded so would it make sense to have a skilled welder fill the pits with cast iron weld rod? It would be tedious work for sure but you may end up with a better result. After the weld filling and grinding of the welded highs is done maybe a course blasting and /or some creative pick hammering to duplicate and restore the original look followed by a cast iron appearing coating if needed. luck. john

[Guest philipswanson]

Phil, If the pits are deep, grinding to eliminate them will change the contour of the piece which I assume you realize. Cast iron blocks can be welded so would it make sense to have a skilled welder fill the pits with cast iron weld rod? It would be tedious work for sure but you may end up with a better result. After the weld filling and grinding of the welded highs is done maybe a course blasting and /or some creative pick hammering to duplicate and restore the original look followed by a cast iron appearing coating if needed. luck. john

Now you are talking. That makes sense. I have also heard of using brass. My son is a welder so I need to get with him. I also have heard that you need to pre-heat the manifold pretty hot before you can do any welding or brazing to it. I was looking for someone that has accomplished this before.

I have talked to allot of folks about a thick coating to fill pits but the concensus was that a thicker coating is going to flake off and cause problems. Even Swain Technologies said that filling pits using porcelin won't work. It's like plating and will make it look worse unless the pits are welded or ground off first. Anybody been through this process?

Thanks, Phil Swanson

[Restorer32]

Never use braze to repair pits in a manifold that is to be porcelainized. The temp of porcelainizing is much higher than the melting temp of braze. Acquaintance of mine learned this the hard way with a Duesenberg manifold of all things.

[Guest philipswanson]

Thanks for that good info. I guess if you braze you could still use a good manifold paint like POR 15 or Eastwood out of the can. There might be a good cast iron rod for this purpose???

Thanks, Phil

[nickelroadster]

One thing that you might want to remember is if you weld the cast iron manifolds it just has to look good, not be super strong. most people who are welding cast iron are concerned about the strength of the weld and this is why they are doing things like preheating the piece. If you can get it to look good, it will probably work fine.

[Guest philipswanson]

Not so worried about strength and do not plan to preheat the whole manifold. According to my son, the welder we don't need to do this with a cast iron rod and stick welding.

Phil

[60ch]

Phil, Welding cast iron is not really difficult you just need to understand what is going on. Welding an ear onto and exhaust flange is easy because the ear is able to shrink as the weld cools. If you are welding welding in any area that is not free to shrink on cooling you will get cracks unless you preheat, then weld while maintaining the preheat and slow cool the part. Some people slow cool by wrapping the part in a fireproof blanket or by burying it in sand. Those that can put the part in the oven and turn the heat down gradually over a period of hours. The part is then left to cool down in the oven with the oven shut off. I have brazed engine blocks and head castings successfully but once built up an ear on a small block exhaust manifold. After a few years I could see that the cast iron was deteriorating at the braze joint. I am not really sure why. It was as if the high heat at the exhaust flange was contributing to electrolisis. Just be careful. When in doubt, preheat . Terry

[Guest philipswanson]

Phil, Welding cast iron is not really difficult you just need to understand what is going on. Welding an ear onto and exhaust flange is easy because the ear is able to shrink as the weld cools. If you are welding welding in any area that is not free to shrink on cooling you will get cracks unless you preheat, then weld while maintaining the preheat and slow cool the part. Some people slow cool by wrapping the part in a fireproof blanket or by burying it in sand. Those that can put the part in the oven and turn the heat down gradually over a period of hours. The part is then left to cool down in the oven with the oven shut off. I have brazed engine blocks and head castings successfully but once built up an ear on a small block exhaust manifold. After a few years I could see that the cast iron was deteriorating at the braze joint. I am not really sure why. It was as if the high heat at the exhaust flange was contributing to electrolisis. Just be careful. When in doubt, preheat . Terry

Terry, Thanks for the good infomation. This is a great post for all the mebers of this forum.

Phil

[Curti]

There is a process known as flame spraying. There is a shop near me that can restore a manifold to an 'as new' condition. The name of the shop is Crow Custom Cast Welding. 715-425-6653

[Guest philipswanson]

Thanks Curt,

I'll give them a call.

Phil

[Guest philipswanson]

UPDATE

We totally welded and ground the manifold and it came out good. Absolutly no preheating done. Definietly not needed with cast iron 1/8 stick welding for cosmetics to fill pits. Ok to preheat for structual repairs but not required for filling in pits. Finish with coarse sandblast (sand from beach) and body pick hammer. Paint with POR 15. Lotsa time grinding. Cost prohibitive to have a shop do it though. Has to be a labor of love or forget it.

Phil Swanson