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U-2 Driver
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stock '72 GT exhast manifold

Just wondering, why can't I just cut off the top of the "stove" from my exhaust manifold and weld a piece of steel over the top? obviously I would have to contour it a bit, but other than that? I think it would be a little cheaper than a sprint. Anyone tried this?
 

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This is not mine, this was John Wargas (Canadian member) doing, and it's his manifold, I have a sprint manifold. But, yes, this is what this site is all about.:D
 

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Opeler
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sprint replica

I am in the middle of rebuilding my head on my 1.9 and while it is apart I was thinking of doing this to my exhaust manifold. I was also thinking of cutting out the web. Any thoughts on this or should I leave well enough alone?
Bob
 

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I am no expert about this but it seems to me that the web on the exhaust manifold obviously adds strength to the part and acts like a heat sink. I would think that you would want to radiate heat away from the exhaust manifold as quickly as possible. You also don't want it getting any hotter around the carburetor than it already is. And you wouldn't want to risk the casting cracking as it heats up and cools. Leave it alone, I would think. Any rough spots in the cut would also form high stress areas and would be prone to starting a crack.

BDD
 

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BDD said:
I am no expert about this but it seems to me that the web on the exhaust manifold obviously adds strength to the part and acts like a heat sink. I would think that you would want to radiate heat away from the exhaust manifold as quickly as possible. You also don't want it getting any hotter around the carburetor than it already is. And you wouldn't want to risk the casting cracking as it heats up and cools. Leave it alone, I would think. Any rough spots in the cut would also form high stress areas and would be prone to starting a crack.

BDD
I've had one with webs removed on my '73 GT since '78. Less weight and doesn't retain as much heat on shutdown.

Otto's "webless" exhaust, next to last post on page 4.

:cool:
 

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Old Opeler
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Welding Manifolds

Welding cast iron is art and alchemy and can result in many cracks.

Using mild steel plate as the filler plate can create different expansion rates when the manifold is heated and cooled in operation.

Maybe the cast iron web can be cut off and used as a plate to fill the hole left by the removal of the stove area.

The best success I have had with welding exhaust manifolds is by using gas welding techniques with Eutectic Castolin fluxed gas rods designed for welding Cast Iron and preheating the manifold to a dull red before welding.

That was for repairing flange bolt holes - attaching a largish bit of plate would be a bit more challenging!
 

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Opeler
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In past experience, the best filler material I have used for joining cast to mild steel is brass. Seems to be more forgiving in expansion and contraction. I have also made repairs in cast using rod made for that purpose. Very tricky and not fun chasing the resulting cracks.
I just looked and I don't think there is enough material in the web to fill the hole unless it is more than one piece.
I am also considering doing away with the under the carb heat shield and fabricating one that mounts just over the modified exhaust manifold. Any thoughts?
Bob
 

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Old Opeler
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Brass

Ordinary "brass" or more correctly Bronze welding rods will not stand up to exhaust heat for long as the Tin oxidises out and the metal goes what is known as "hot-short" and recrystalises into much larger crystals and powders away.

"Steel Braze" which is Nickel bronze rather than Tin bronze will stand up better but still "hot-shorts" after repeated heating and cooling - especially if the exhaust manifold gets over-heated due to retarded spark or lean running - or both! You can get by for a while with Eutectic Castolin 185FC which is a flux coated Nickel bronze rod.

Electric Arc or (heaven forbid) Mig welding cast iron is LOTS of fun: NOT!

This leaves gas welding with hitech filler rods - though I have used electric arc nickel rods with the flux bashed off as fillers in moments of despairation. However the Eutectic Castolin fluxed cast iron rod is the best I have used. A while go and the actual designation of the rod eludes me. Very helpful!

Just putting a stainless steel plate under the intake manifold after machining a bit more room is another - easier - option.....
 

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GTJim
What manifolds are used on the Holdens? Anything sprint like that might be exportable?
 

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Old Opeler
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Holden Manifolds

The Opel engines in Holden "Sunbirds" are swept back and much larger in the exhaust outlets - and prone to cracking. I only have two good ones!

Pic:
 

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That is a rather "special" exhaust manifold. The only way I've had any luck welding exhaust is like Jim said. Get it good and hot with gas first and then throw the electric arc to it with alot of power. I used mild steel rod and it held for years. This was on the bolt ear for a sprint used in a turbo application, so it saw alot of heat. It was also a stress point as the plumbing for the turbo layed out. I tried the bronze and other things first and they all cracked and broke in pretty short periods of time. If I remember right I did this with it still in the car. After three or four previous attempts I was getting a bit sick of it, removing that manifold was an all day job.
 
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