Heat riser issues
Thread Starter
Racer
Joined: Nov 2004
Posts: 319
Likes: 0
From: Sunnyvale CA
Heat riser issues
Ok so I had my car down at the shop a few weeks ago for some reason, and they told me when I picked it up that the heat riser was messed up somehow and that I should fix it with "heat riser solvent". Anyone have any experience with this? I thought that it might also explain why the car runs so bad when I start it up cold in the morning...
Race Director
Joined: Aug 2004
Posts: 10,628
Likes: 132
From: Duvall, WA
Heat riser solvent is very handy to have on hand. I used some to clean my muffler bearings just the other day.
(kidding)
You can get heat riser solvent at your local GM dealer. It will prevent your heat riser from closing in one position.
(kidding)
You can get heat riser solvent at your local GM dealer. It will prevent your heat riser from closing in one position.
Drifting
Joined: Mar 2005
Posts: 1,806
Likes: 3
From: Burlington WI
First...
Lash the car down with about 100' of flight line and then mix equal parts of prop wash and heat riser solvent. Then hold the RPM's between 3,000 and 5,000 and slowly pour the mix down the throat of the carburetor. This should knock any carbon build-up out of the combustion chamber and it won't get away from you in the process.
In other words... sounds like BS to me
In other words... sounds like BS to me
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
You can lube it or just wire it open. The heat riser siezes and causes the passenger side of the exhaust to rust out prematurely. It can also cause the carb to get baked. I do think GM sells a lube for it but have never used it. I replaced mine with an open spacer designed for a fuel injection engine on one car. My '80 Vette heat riser works on vacuum but is not connected. No problems there as it defaults to the open position. Many early C3's use a bi-metalic coil to operate and are more vulnerable to siezing.
-Mark.
-Mark.
Le Mans Master
Joined: Mar 2004
Posts: 7,458
Likes: 1,484
From: Little Rock AR
Have you considered replacing it? They are like $40 or so. I would first see if you could free it up then try using it as is. They can be troublesome. Solvent is reccomended for cleaning. If you could get it free I might try some graphite spray on it. Never tried it myself but it might work. 
Ask at the dealership what they would use for lube.
-Mark.
Ask at the dealership what they would use for lube. -Mark.
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
Now that everyone has gotten the jokes out of their system, here is the real deal. If you have a frozen heat riser, it either is frozen open or shut. Open, it will make warm up take longer and closed, you will loose power. You MIGHT be able to "free it up" by using something like PB blaster around the "flapper" and letting it soak in and trying to free the flapper. More likely than not, it will be rusted inside where you cannot get at it and the pivot points are all fked up with rust. To replace it means taking the bolts out at the exhaust manifold studs, which if they haven't been done before, could be a problem. If those bolts and studs are rusted to a point, they might bust getting them off. They have to be soaked for a few days in PB blaster so you can get the nuts off. The studs may be thinned out by rust. To get the studs off for replacement, you have to take the manifold off and with a torch, heat them up and get them out. 
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
And the heat riser, functioning or not, will not affect how the car behaves upon cold start up. It affects how quickly the manifold heats up to help vaporize the fuel but before the manifold starts heating up, again, it has no affect at the point where the engine fires.
So if the car runs crappy as soon as you fire it up, it isn't the heat riser. How it runs a minute or so after fire up, yes, but not before then.
So if the car runs crappy as soon as you fire it up, it isn't the heat riser. How it runs a minute or so after fire up, yes, but not before then.
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