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Considering deleting my stock exhaust heat riser valve in my Olds. The spring broke off, it was jammed, rusted, and I’m not even sure it’s stuck in the open position so that the exhaust can escape properly. I’d like to remove it completely, since I don’t drive the car after October anyway. It is hibernating for the winters. Do I need to fabricate something to fill the gap? Does anyone know where I can order the chunk to make the bridge between the exhaust manifold and the rest of the exhaust tubing where the valve will be missing?
Check first maybe it is stuck open, if not you could grind off the internal flap. I've not done this but I think some remove the shaft completely and braze the holes closed.
Check first maybe it is stuck open, if not you could grind off the internal flap. I've not done this but I think some remove the shaft completely and braze the holes closed.
And then weld the cast plugs into the intake crossover passages and eliminate all the heat under the carb.
The divorced choke, if equipped, can be adjusted to work or convert to electric.
One of the best mods I've done to my 68 400.
Check first maybe it is stuck open, if not you could grind off the internal flap. I've not done this but I think some remove the shaft completely and braze the holes closed.
That didn’t even dawn on me, to just get rid of the flap inside. Going to have to let the penetrating oil concoction soak on those bolts for a while I think.
And then weld the cast plugs into the intake crossover passages and eliminate all the heat under the carb.
The divorced choke, if equipped, can be adjusted to work or convert to electric.
One of the best mods I've done to my 68 400.
Interesting. I’ve never had issues with the carb receiving too much heat since I’ve added the stack of phenolic plates I think. Used to have issues, but none for a long time, on the fuel side of things with the carb.
I’d also like to not do a lot of “tinkering” and extra welding to the car. Trying to keep her as original as I can. I did track down an original Harrison radiator that came stock with her. Looks great, feels great, deleted the H2O gauge I installed and I simply rely on the ‘dummie’ lamp. Takes a little stress and anxiety away 😂
Ya I here ya on originality.
Removing the valve, its spring, and shaft from the manifold is a subtle upgrade.
Only a trained eye or a PV evaluation on a museum car wouldn't pass the originality test. (PV = performance evaluation in NCRS Vette speak).
You could source another manifold to weld on.
The cast block off plugs in the intake are meant to be installed into the heads. But I chose to recess them into the intake and spot welded them in. They could be removed. You cant see this modification.
I needed to solve recurring hot a starting problem from fuel boil off, and I was in search of ways to increase HP with out adding aftermarket crap.
This mod cured the hot starting. AND the paint doesn't burn off the intake. I installed 69 400/455 exhaust manifolds in my 68. Still have the mint 68s on a shelf
Another idea is to tap the shaft holes for a nominal size close to what you have after cutting the flapper and shaft out. Screw in a set screw or bolt with some pipe dope.
Last edited by OLDSter Ralph; Jul 31, 2025 at 09:24 PM.
Considering deleting my stock exhaust heat riser valve in my Olds. The spring broke off, it was jammed, rusted, and I’m not even sure it’s stuck in the open position so that the exhaust can escape properly. I’d like to remove it completely, since I don’t drive the car after October anyway. It is hibernating for the winters. Do I need to fabricate something to fill the gap? Does anyone know where I can order the chunk to make the bridge between the exhaust manifold and the rest of the exhaust tubing where the valve will be missing?
Originally Posted by Sugar Bear
Is this on the 61 '98 in your signature?
Originally Posted by eggydrummer
That is correct.
Originally Posted by droldsmorland
Ya I here ya on originality.
Removing the valve, its spring, and shaft from the manifold is a subtle upgrade.
Only a trained eye or a PV evaluation on a museum car wouldn't pass the originality test. (PV = performance evaluation in NCRS Vette speak).
You could source another manifold to weld on.
The cast block off plugs in the intake are meant to be installed into the heads. But I chose to recess them into the intake and spot welded them in. They could be removed. You cant see this modification.
I needed to solve recurring hot a starting problem from fuel boil off, and I was in search of ways to increase HP with out adding aftermarket crap.
This mod cured the hot starting. AND the paint doesn't burn off the intake. I installed 69 400/455 exhaust manifolds in my 68. Still have the mint 68s on a shelf
Another idea is to tap the shaft holes for a nominal size close to what you have after cutting the flapper and shaft out. Screw in a set screw or bolt with some pipe dope.
That's a good idea if the OP doesn't want to take the manifold and get it welded. You could even get Allen screws without a head and recess them in the manifold with some heat resistant Locktite. This would be virtually in invisible.
BTW, my 64 98 had one of those heat riser valves that was seized. I just removed the flapper and had the shaft in the exhaust manifold still. I actually had a heated port on the bottom of the intake manifold welded closed by a shop and went to an electric choke.
Another idea is to tap the shaft holes for a nominal size close to what you have after cutting the flapper and shaft out. Screw in a set screw or bolt with some pipe dope.
Originally Posted by Olds64
That's a good idea if the OP doesn't want to take the manifold and get it welded. You could even get Allen screws without a head and recess them in the manifold with some heat resistant Locktite. This would be virtually in invisible.
BTW, my 64 98 had one of those heat riser valves that was seized. I just removed the flapper and had the shaft in the exhaust manifold still. I actually had a heated port on the bottom of the intake manifold welded closed by a shop and went to an electric choke.
There is NO REASON to get it welded if you plug it with a set screw or bolt. 1/2 hour to measure the id and tap to the closest screw thread is a "no brainer". There may also be enough room on the inboard side to tap without removing the exhaust manifold. You also don't need 75% of full threads to make it work.
Bolts generally have hex heads or Allen head socket heads (S.H.C.S.). Set screws typically have "no head: and have Allen head" or other means (slots, phillips, etc.) to screw them in.
