Crack in manifold: How to repair?

[bikemaniac]

Hi,

I just realized that I have a fine crack in my exhaust manifold, approx 2 inches long and it is located on the large diameter section. When the car is running I cannot feel any exhaust gasses when approaching close by with my hand. What method can be used to fix the crack - or can I just leave it as is?

The crack is located such, that you could actually weld/braze it without removing the manifold assembly.

Lucas

[Mike V. Florida]

There is a company called Muggyweld that claims to have rods that will work on cast. I would replace it if it were me with a new from the vendors.

[C26Pinelake]

Originally Posted by Mike V. Florida

There is a company called Muggyweld that claims to have rods that will work on cast. I would replace it if it were me with a new from the vendors.

I just did exactly that. Purchased a new manifold and gaskets from A & L.
My mechanic was impressed with the quality.
Wayne

[Terry,NJ]

Seeing that you're in Denmark, you may not want to pay the high shipping charges that would be incurred on an item such as a manifold. You may want to try the "Muggyweld" or a similar European product.
Terry

[Synchro909]

Welding cast iron can be done but not by just anyone. Shrinking and warping can also be a problem on a manifold. An exhaust manifold will have absorbed so much carbon over the years that they are pretty much impossible to weld properly. I had a crack in the manifold of a car I bought recently. I didn't even try welding it - just put on a new one. Any extra $ above the cost of getting it welded are more than worthwhile.

[vermontboy]

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Back in the 60's I used stove cement covered by asbestos cloth and a piece of sheet-metal bent to fit and wired on - it lasted the two remaining years I used it as a daily driver. Not sure if there is any modern equivalent to asbestos cloth.

[Y-Blockhead]

Originally Posted by vermontboy

Back in the 60's I used stove cement covered by asbestos cloth and a piece of sheet-metal bent to fit and wired on - it lasted the two remaining years I used it as a daily driver. Not sure if there is any modern equivalent to asbestos cloth.

Is your name "Jury (Jerry)" by any chance?? As in Jury (Jerry) Rig??

[holdover]

welding cast is a iffy item, sometimes works, most often it doesn't. I'm sure there is a welding shop over in your area that specializes in that kind of work, but you are taking a chance.. It it was me I would replace it. Best of luck

[H. L. Chauvin]

Hi bike,

"If" you decide to try normal welding on your manifold, the types of welding rods are most important; & FWIW:

1. Cast iron is a material somewhat similar to concrete with very high compressive strength & very, very low tensile strength.

2. The small cast iron area welded gets very hot with the welding rod or torch welding process & this particular area of cast iron expands rapidly ..... when finished with welding this expanded, heated welded area cools & shrinks rapidly ..... the cast iron does not fail & crack at the weld; but with the cooling & pulling adjacent tension forces, the cast iron fails on the rapidly shrinking sides of the weld.

3. Vintage welders were fully aware as to where this shrinking cast iron failure occurred, so in many cases on small parts such as manifolds, one person would do the welding & one person would heat the entire manifold with a torch.

4. The welded area would get very hot with welding, but the surrounding areas would also be heated with a separate torch; hence, the entire manifold would be hot during welding. Next, to reduce shrinking & cracking, when the welding was finished, the torch guy continued to heat the cast iron area adjacent to the weld & all over to avoid temperature differentials.

5. Larger parts where placed in hot coals, slowly heated, then welded, then thrown back into the hot coals & allowed to cool to ambient temperature for several hours.

6. In our rural area I knew two such famous cast iron welders years ago who specialized & were always 100% successful in welding cast iron engine blocks & other cast iron items that parts manufacturers deemed impossible. Both were born right after WWI -- nobody continued with their particular cast iron welding accomplishments.

7. Muggy Weld requires far less heat.

The above may prove helpful only "if" your sights are truly aimed at "trying" welding cast iron.

Appears the only truly successful self-employed folks I ever knew in life were always the one's who experimented with unknowns & took chances -- if this tried method fails, just one more experience stored between your ears -- you can always later call a Model A vendor for a new manifold.

[Purdy Swoft]

In the distant past, I've brazed exhaust manifolds but don't recommend it. If you possibly can, just replace the manifold. If you were able to successfully weld- braze up the crack, the fumes from welding exhaust parts may make you sick. It allways made me feel purdy bad any time that I welded exhaust parts.

[Purdy Swoft]

Just to add a word, If you do attempt welding-brazing the manifold, Have a box of sand and cover the manifold with sand while it is hot so as to hold the heat so it doesn't cool too quickly.

[Terry,NJ]

Welding cast iron manifolds is near to impossible! But if you want to try, heat nthe manifold to a red hot and let it stay there for a while. C I is very porous andf you have to get some of the carbon out of the metal. Welding carbonized C I is like trying to weld a hot frying pan with an icicle. The metal just spalls off in little balls. Don't bother with Ni-rod. Use the cheapest steel rod you can find, 6013 and feed in 6011 with your other hand. Weld stringers back into the solid material first. These stringers will give your weld something to grab onto. I don't recommend doing it. I've spent an afternoon with every kind of rod I had, Ni-rod, stainless, 6013, 6011, 6010, 7018 and still couldn't get a weld. The parent metal was too carbonized.
Terry

[tbirdtbird]

Whatever you end up doing for a repair (I agree with those that say cast is nearly impossible to weld; Ni rods are a joke in my opinion), be sure not to over-torque the nuts! This is the reason for most failures. The manifold expands and contracts considerable based on temp and it needs to be able to move around behind those nuts.

[PC/SR]

I would suggest if it is not causing a problem, and since it is not an easy fix, and you can see it, let it go, just keep an eye on it.

[H. L. Chauvin]

Hi bike,

If you decide to buy a new exh. manifold, you may want to ask the Model A parts vendor if his new exh. manifolds are made by the same company as his new int. manifolds &, if they are perfectly aligned as a matched set.

I asked & bought a matched set from Bratton's to insure a tight fit that had perfect alignment & absolutely no leaks.

Old cast iron manifolds often get warped & require having the gasket contact surfaces milled to align same.

A leaking intake manifold is as harmful as a carburetor leaking air where the carburetor half's mating surfaces meet the gasket.

Hope this helps if you are choosing to buy a new exh. manifold.