Lying under my 71 LS5 I discovered that the RH exhaust pipe to exhaust manifold was loose. The exhaust system is pretty new, done by previous owner.They had used long brass nuts over the old studs which tighten down easily. I then noticed that the heat riser was missing from the heat valve assembly. Their are two bolds on either side now. Engine is rumming fine so I believe there is no problem with the heat riser or the lack of one. Is it possible to tell if there is any blockage inside without removing exhaust system? The car has a flowmaster system. Is it possible to replace without removing exhaust pipe? Is it advisable to take system apart to install a new heat riser or will it run fine without one?
-
-
Re: Heat Riser
Ed-----
It sounds like what someone has done is to remove the "guts" of the heat riser valve so as to make the valve inoperable. Using bolts to plug the shaft holes in the valve body casting is a little crude, but it should be functionally very effective. If the valve is to be eliminated, then either the existing valve body has to remain as a spacer or a purpose-manuafctured spacer installed (as was used for 63-65 FI Corvette engines).
Heat risers are often eliminated in order to reduce the deterioration of the right side muffler and, in my opinion, it's a VERY good and advisable thing to do. If one wants to do this while preserving original external configuration, one can simply remove the internal valve plate from the valve and leave the shaft, external thermostat spring, and counterweight. In this sense, the external appearance will look stock, but the valve will be non-fuctional. If exact original configuration is not necessary, then the approach that someone took with your valve will work just fine and accomplish the same purpose. Or, as I say, a spacer available from reproduction sources can be used.
The valve cannot be removed from the car without first removing the forward exhaust pipe.In Appreciation of John Hinckley -
Re: Heat Riser
Ed-----
It sounds like what someone has done is to remove the "guts" of the heat riser valve so as to make the valve inoperable. Using bolts to plug the shaft holes in the valve body casting is a little crude, but it should be functionally very effective. If the valve is to be eliminated, then either the existing valve body has to remain as a spacer or a purpose-manuafctured spacer installed (as was used for 63-65 FI Corvette engines).
Heat risers are often eliminated in order to reduce the deterioration of the right side muffler and, in my opinion, it's a VERY good and advisable thing to do. If one wants to do this while preserving original external configuration, one can simply remove the internal valve plate from the valve and leave the shaft, external thermostat spring, and counterweight. In this sense, the external appearance will look stock, but the valve will be non-fuctional. If exact original configuration is not necessary, then the approach that someone took with your valve will work just fine and accomplish the same purpose. Or, as I say, a spacer available from reproduction sources can be used.
The valve cannot be removed from the car without first removing the forward exhaust pipe.In Appreciation of John HinckleyComment
-
Addendum
Also, the exhaust manifold can be removed, in many instances, as an alternative to removing the forward exhaust pipe in order to replace and/or remove the heat riser valve.In Appreciation of John HinckleyComment
-
Addendum
Also, the exhaust manifold can be removed, in many instances, as an alternative to removing the forward exhaust pipe in order to replace and/or remove the heat riser valve.In Appreciation of John HinckleyComment
-
Thanks Joe - *NM* *NM*
Comment
-
Thanks Joe - *NM* *NM*
Comment
-
Re: Thanks Joe -
The brass nuts being loose are not unusual in a newly installed system. I always check mine after a few hundred miles to make sure they are still tight so that it will not destroy a gasket. I agree with Joe, the heat riser just destroys the exhaust system and I have not had a functional heat riser on my 68 or 70 since they were new, just wired them open.Comment
-
Re: Thanks Joe -
The brass nuts being loose are not unusual in a newly installed system. I always check mine after a few hundred miles to make sure they are still tight so that it will not destroy a gasket. I agree with Joe, the heat riser just destroys the exhaust system and I have not had a functional heat riser on my 68 or 70 since they were new, just wired them open.Comment
-
Re: Heat Riser
What is the mechanism by which the heat riser causes the right side exhaust to deteriorate?
Thank God I eliminated this instrument of the devil in my new system.Comment
-
Re: Heat Riser
What is the mechanism by which the heat riser causes the right side exhaust to deteriorate?
Thank God I eliminated this instrument of the devil in my new system.Comment
-
Re: Heat Riser
This is how I understand the mechanism "works": The heat riser valve blocks the exhaust in order to heat the intake manifold during the engine warm-up period. So this side of the exhaust heats up slower than the driver side. This is why moisture in the exhaust does not evaporate completely unless you drive longer distances when both sides of the exhaust are hot. The moisture together with the exhaust gas build sulphurous acid which corrodes the exhaust.Comment
-
Re: Heat Riser
This is how I understand the mechanism "works": The heat riser valve blocks the exhaust in order to heat the intake manifold during the engine warm-up period. So this side of the exhaust heats up slower than the driver side. This is why moisture in the exhaust does not evaporate completely unless you drive longer distances when both sides of the exhaust are hot. The moisture together with the exhaust gas build sulphurous acid which corrodes the exhaust.Comment
-
Re: Heat Riser
Here's another explanation. When the valve is closed exhaust gas if forced up under the manifold to the LH exhaust pipe, and there is very little exhaust flow through the right side system. You can check this by placing your hand over the exhaust pipes while the engine is warming up.
Because of the low flow rate, water vapor, which is a primary exhaust gas constituent cools rapidly and condesces out. This increases the rate of corrosion. My RH muffler rotted out in five years. At that point I wire the heat riser valve open.
DukeComment
-
Re: Heat Riser
Here's another explanation. When the valve is closed exhaust gas if forced up under the manifold to the LH exhaust pipe, and there is very little exhaust flow through the right side system. You can check this by placing your hand over the exhaust pipes while the engine is warming up.
Because of the low flow rate, water vapor, which is a primary exhaust gas constituent cools rapidly and condesces out. This increases the rate of corrosion. My RH muffler rotted out in five years. At that point I wire the heat riser valve open.
DukeComment
Comment