# exhaust dampner



## Topkat (Sep 9, 2010)

The dam exhaust "dampner" on my 67, on the passenger side broke. The dam pin that holds the spring rusted off. 
I understand it helps heat up the motor in cold weather, .......
My question is this..............is the flapper open when the weight is straight up and down? It seems like it is.
I wrapped safety wire around it for now.....I just worry the wire will eventually break and the valve close when im out and about. I cant afford a new manifold and don't want to really raise the motor do take the manifold out and remove the flapper.
thanks as always
Tk


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## rickm (Feb 8, 2012)

if you drive it and its closed, its possible to crack the passenger side head from heat.


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## Old Goat 67 (Feb 2, 2009)

Weight was there to pull it down when bi-metal spring loosened up with heat, gravity thing you know.

Flapper is open inside when weight is horizontal.

If you have it wired in the up position, you have it closed.

Unless you live in the frigid nawth, it is not needed.


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## Topkat (Sep 9, 2010)

Up is closed?? :banghead:


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## hotcharity95 (Jan 4, 2015)

*what is it for?*

what is it for?


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## Old Goat 67 (Feb 2, 2009)

To heat the base of the carb.


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## Lemans guy (Oct 14, 2014)

We called these things heat riser valves.....as said the spring kept it closed when cold so that exhaust was routed under a passage in the intake underneath the carb....it forced all the exhaust out through that passage under the carb and through the other manifold....once heated it opened and exhaust went out as normal.

They always stuck and broke and rusted and you have to keep 'em lubricated...

Use PB Blaster to free up stuck ones.....anyway I took my manifolds out and used the HO manifolds, no heat riser at all..

If you can't make it move freely from lots of blaster on hinge, the wired open is fine....I don't notice any difference, as long as you have a good working choke system..now in very cold climate sure it may help, but it only stay closed a few minutes...like a choke...


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## pontiachristopher (Jun 28, 2020)

Topkat said:


> The dam exhaust "dampner" on my 67, on the passenger side broke. The dam pin that holds the spring rusted off.
> I understand it helps heat up the motor in cold weather, .......
> My question is this..............is the flapper open when the weight is straight up and down? It seems like it is.
> I wrapped safety wire around it for now.....I just worry the wire will eventually break and the valve close when im out and about. I cant afford a new manifold and don't want to really raise the motor do take the manifold out and remove the flapper.
> ...


thats the flapper on the passenger side exhaust manifold? found one on a 1968 bonneville 400 with single exhaust, when i changed to dual exhausts, changed the exhaust manifold out with a solid one


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