Removed exhaust manifold and found something interesting

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SeattleQQ1Fish

SeattleQQ1Fish

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I decided to pull the heads off my 273 to change the valve seals, scrape off 50 years worth of grime, etc.. I pulled off the passenger side exhaust manifold and found the manifold heat control valve welded about 70% of the way closed. Is there any reason for someone to do this? What was that doing to the performance of my car? It never has run right.. My first instinct is to saw the thing off, plug the hole and forget about it. Is that going to cause any issues?

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Here is the sleazy little weld they closed it with
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My riser spring has been gone forever. (Fully open) all the time I live in Colorado. Two winters and I have not had an issue starting or running. It is probably choked more than needed for longer than needed. But no drivability issues. Should mention 273 2bbl.
 
It probably didn't affect exhaust flow as much as you would think, and only at very high rpms. Having an operational heat control valve helps with quicker warm ups in cooler weather.
 
Hellrats said:
Someone got tired of hearing it rattling and welded it
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or somebody got tired of hearing it rattle and welded in place but carbon build up made the welder think is was wide open.
Don't ask me how I know that scenario. LOL!
 
If one wanted it to be fully operational....... aren't there repar kits for that?

Myself, I’d just remove it.
 
I removed mine, shaft and all. There are SS sleeves cast into the manifold where the shaft rides on both sides. I took mine to a machine shop, had them remove the SS sleeves and braze the holes closed.
Electric choke carburetors don't need the damn things!
 
DesertRat said:
I removed mine, shaft and all. There are SS sleeves cast into the manifold where the shaft rides on both sides. I took mine to a machine shop, had them remove the SS sleeves and braze the holes closed.
Electric choke carburetors don't need the damn things!
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You could take it out , tap the holes and screw a bolt in the holes ---
 
famous bob said:
You could take it out , tap the holes and screw a bolt in the holes ---
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Yeah I looked at that but decided 1-that stainless steel is hard to tap and 2-threading and plugging cast iron with huge temperature swings is asking for a crack. (and not the good kind)
 
DesertRat said:
Yeah I looked at that but decided 1-that stainless steel is hard to tap and 2-threading and plugging cast iron with huge temperature swings is asking for a crack. (and not the good kind)
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I have removed a couple of those risers and used 2 short stove bolts from the inside with nuts on the outside.
(Stove bolts have the flatish rounded head) so they don't cause any restriction, and if you wish you can grind the nut side down quite a bit.
 
Weld the hole. Just little tack welds, dont heat it up much.
 
The first time I removed the pass. side manifold on my '67 273, I found the valve frozen completely closed, so exhaust from that side was being forced through the intake heat passage constantly. I just tapped the weight with a hammer to open the valve fully, and it's remained frozen there ever since. I only drive the car in good weather, so no need for a heat riser anyway.
 
that is one of the 1st things I check when I buy an older car. I've found two that were frozen shut. I usually remove them and put carriage bolts in there, the head of the bolt on the inside.
 
Can just cut that heat riser out. There are steel sleeves in the manifold where the butterfly pivot pin goes through.

Weld the steel sleeves shut with a wire feed welder.

Done Deal

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Seattle,
If you have single exhaust, that butterfly is supposed to act as a baffle. You wouldn't need it if you changed to dual exhaust and an electric choke.
Since you have the heads off, you could also block off those heat riser ports, partially or totally with fabricated metal pieces or intake manifold gaskets without a hole for that passage. Those are thicker though and would raise the intake manifold up a little, requiring the cork gaskets on the china rails. Totally blocking the heat riser ports would make the center of the intake manifold very cold but could reduce carb overheating.
Any other work planned for the heads?
 
Richard Sweet said:
If you have single exhaust, that butterfly is supposed to act as a baffle. You wouldn't need it if you changed to dual exhaust and an electric choke.
Click to expand...
The car originally came with single exhaust, but that was gone probably decades ago.
 
George Jets said:
Can just cut that heat riser out.
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I'm attempting to do that now. I cut off the sides flush with the manifold, and I can see the steel sleeves, but the valve inside is still completely seized. Should I have someone drill them out, or maybe I can just get in there with a hacksaw blade?
 
A BFH will loosen that thing up. Or the more civilized approach would be to chuck a coarse burr in a die grinder and start whittling away at the disc where the shafts go into it. It'll fall apart eventually.
 
I had about the same thing with a 340 HP manifold, but in the process of removing the stuff, one of those steel sleeves came out. I took that to a machine shop, and the guy made me 2 solid plugs. I knocked the other sleeve out, and replaced them with the plugs he made me. They have been on the engine in my Challenger since 1990, and never a problem. Plus side is, the manifold could be easily put back to original with a now available heat riser kit. Not gonna happen in my lifetime! LOL
 
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