I have a 79 vert and I'm wondering is the heat riser a needed item for the exhaust? If so is it only on the RH exhaust manifold or is one needed on both sides? I'm using stock exhaust manifolds until I send my headers out to Jet Hot. Must you use copper gaskets or the ones that came with my gasket kit?

 

Only one riser is normal usually on the right side exhaust. I don't use one, I bought a spacer and gaskets from a Midas muffler shop, they charged me $15.00 for them. Seems like I used one gasket it was a 3 hole triangular gasket and one fiber donut, that goes between the top of the riser or spacer and the bottom of the manifold. The three bolt hole gasket goes on the bottom. This is for a 69 model, it might be different on your year model, but I think they are pretty much the same.

 

My 81 only has the heat riser on the right side only. Hope you don't mind a few more questions on this post. Anyone replace the heat riser on an 81? Where did you get the spacer? What exactly is the heat riser for? Any adverse effects on performance by getting rid of the heat riser?
Thanks
:cheers:


[Modified by bertmeister, 9:16 PM 10/18/2003]

 

The riser is normally closed when the engine is cold, when the engine is started exhaust gas is held in check by the flapper of the riser and forced through the crossover in the manifold. This heats up the manifold, I think it was supposed to speed up warm up. Some modern heads and intake manifolds don't have an exhaust crossover through the heads and intake manifold. If they have an EGR then it is usually plumbed directly from the exhaust manifold to the EGR.
As far as performance goes, I think that having hot exhaust gas flowing through your intake manifold would actually reduce performance, by heating the air fuel mixture. Manifolds like the Edelbrock Air Gap are designed with this in mind, relatively cool air is allowed to circulate under the intake runners to keep the charge cold.
As far as the spacer for an 81, I've not seen an 81 with stock exhaust manifolds in a long time, I have a friend that has an 81, but he has headers on his car.
I'd suggest that if you have the riser off the manifold, go to a muffler shop with it and see if they have a matching spacer that will replace it. That's what I did, just by chance I stopped by a Midas near my house, with riser in hand. They had a solid spacer that was exactly the size and shape of the old riser, it just didn't have a flapper or spring. I also got the donut gasket for the top of the spacer, and the right metal/composite three hole triangular gasket for the bottom.

 

Thanks for the info.
:chevy