Heat Riser Valve

[Juliet P.]

What is the lifespan of a Heat Riser Valve? I replaced mine about 2 years and 11k miles ago and goobered it up pretty well with anti-seize at the time. The thing is now sticking again. Am I supposed to be performing regular maintenance on this bugger or what? I now know why the one I took off the car when I first got it was coat hanger wired open. Thanks, ~Juliet

http://corvetteforum.net/c3/1970registry/1970Registry.html

[Joe L.]

Re: Heat Riser Valve

Juliet-----

Heat riser valves lead a pretty "tortured" life with the heat which they experience. The first thing to go is usually the spring and, although a seperate spring used to be available, it no longer is serviced seperately, at least not be GM.

However, there is some regular maintenence that you can perform on the valve which will help reduce or eliminate the sticking. That is to lubricate the valve with GM Heat Riser Valve Lubricant. Spray this liberally around the shaft and counterweight and do it fairly often (like every 3 months, or so). This product is available under GM #1052627. It's also one of the best penetrating oils that you'll find for loosening other rusted and stuck fastners.

[Juliet P.]

Thank you Joe. *NM*

[Duke W.]

Re: Thank you Joe.

Your problem might be the anti-seize compound you used. Conventional anti-seize compounds will oxide from the exhaust heat leaving behind a residual that will likely cause the valve to stick. There are "high temperature" anti-seize compounds available for installing O2 sensors, but anti-seize compounds are not designed to lubricant moving parts. They're designed to prevent seizing in static applications such as fasterners. Your best is to install that valve dry and periodically use the lubricant specified by Joe.

Testing the valve is easy. when cold the counterweight should be pointing to the rear and you should be able to rotate it down 90 degrees with finger pressure. When the engine is at operating temperature, the counterweight should be pointing down.

Duke

[Dave Suesz]

I'm still using the original...

...on my '55. All I have ever done is keep it clean. Of course, the car has been garage kept since 1963.

[Jim T.]

Re: Heat Riser Valve

Juliet I have found that if you wire the heat riser open that your exhaust system will last longer. Living in Dallas my new 70's muffler on the right side was the first to go after about 2 years and wired mine open to get all the hot exhaust I could.

[Joe L.]

Re: Heat Riser Valve

Jim-----

Yes, heat riser valves have probably "sold" more right side mufflers than all other causes for replacement COMBINED. As long as ambient temperatures are not too cold and the heat crossover passage is not blocked or otherwise lacking, enough exhaust heat will diffuse into the passage to allow sufficient carb pre-heat and proper choke operation.

[Patrick H.]

Re: Heat Riser Valve

Joe,

Would it be useful on a summer-only driven car to swap the heat riser to the spacer as used in the fuel injection cars? I have a theory that it also causes premature wear and cracking of the passenger's side exhaust manifold, at least on 71's.

Patrick

[Duke W.]

Re: Heat Riser Valve

I lost the RH muffler on my SWC in 1966, so I wired the heat riser open. I lived in Seattle then. When I moved to Wisconsin to go to grad school the wired open heat riser did not cause any problems in cold weather.

When I rebuilt the engine I replaced that PIA heat riser valve with and FI spacer - damn the points, and I doubt if the car will ever see a cold start below about 45 degrees.

Go the the FI spacer Patrick, but I don't think the heat riser has anything to do with exhaust manifold cracking.

Duke

[Juliet P.]

Re: Heat Riser Valve

Thanks for all the inputs here & offline. All I can say is you're really testing me with all this anti-purist not as factory discussion!! ~Juliet

[Patrick H.]

Re: Heat Riser Valve

Juliet,

The spacer was a factory-installed part - just not in 70 or 71!

Patrick

[Joe L.]

Re: Heat Riser Valve

Patrick------

Absolutely! In fact, my "ZL-1" (if and when I ever get it put together) is going to have a spacer rather than the heat riser. Two different spacers are available, though. The 2-1/2" is for 62-65 small blocks with 2-1/2" exhaust and 65-74 big blocks. The 2" is for all 62-65 small blocks with 2" outlet manifolds and all 66-74 small block.

[Duke W.]

Re: Heat Riser Valve

I think the 2" spacer would also apply to 283 FI cars and can be used on any system with 2" manifolds.

Duke

[Patrick H.]

Re: Heat Riser Valve

Joe,

We're coming in August and expect a ride.

Patrick