3887024 Heat Riser Valve 1967 327/300hp

[Timothy B.]

I wanted to ask if anyone has noticed a difference in the function of aftermarket vs GM heat riser valves and there springs not allowing valve opening after engine warm up.

I believe my 67 has a aftermarket H/R valve and I am experiencing that after warm up the valve stays just about closed. With slow cruising the gasoline in the accelerator pump vaporizes and makes driving difficult so I wired the valve open. I painted the valve with the exhaust manifolds a long time ago with that high heat exhaust paint so the thermostat spring is painted also and I wonder if that's the reason why it does not expand and open the valve more when hot. Could the painted spring be a problem?

All comments are appreciated

[Joe L.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

I wanted to ask if anyone has noticed a difference in the function of aftermarket vs GM heat riser valves and there springs not allowing valve opening after engine warm up.

I believe my 67 has a aftermarket H/R valve and I am experiencing that after warm up the valve stays just about closed. With slow cruising the gasoline in the accelerator pump vaporizes and makes driving difficult so I wired the valve open. I painted the valve with the exhaust manifolds a long time ago with that high heat exhaust paint so the thermostat spring is painted also and I wonder if that's the reason why it does not expand and open the valve more when hot. Could the painted spring be a problem?

All comments are appreciated

Timothy-----


I very much doubt that the paint on the thermostatic spring would affect the operation of the valve.

The original GM #3887024 valve was discontinued many years ago and replaced by GM #362652. The latter is still available from GM to this day. However, I'm not sure that it's really different than the valves sold in the aftermarket. I can tell you that the 362652 valves that I've used worked just fine.

[Tom D.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

You can also buy a spacer to replace the valve. You probably are not driving in the winter anyway...

[David L.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

Here's a photo of a NOS 3887024 heat riser valve.

Dave

[Rob M.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

Timothy,

I replaced my (believed) original with an aftermarket heat riser valve because the original was basically stuck open. The new one doesn't seem to stay open even when at normal operating temps. It opens more when the rpms are go up. I have no idea why that is, or if it's normal, so I wired it open.

FWIW

[Joe L.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

Timothy,

I replaced my (believed) original with an aftermarket heat riser valve because the original was basically stuck open. The new one doesn't seem to stay open even when at normal operating temps. It opens more when the rpms are go up. I have no idea why that is, or if it's normal, so I wired it open.

FWIW

Rob-----


What you describe is normal for a heat riser valve.

[Timothy B.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

Thanks everyone for posting, my experience is similar to Rob's in that the valve wants to stay more toward the closed position and with low speed driving the plenum is getting to hot with ethonal fuel and thus the accelerator pump problem. I don't think any fuel is boiling in the float bowl just the pump cavity.

The only other option is to put a heat shield under the carburetor, something that extends beyond the float bowls to keep the heat off the accelerator pump and leave the heat riser alone. I suspect all aftermarket parts which is why I questioned the aftermarket H/R thermostat spring but never had any issues until last summer.

[Brian M.]

Re: 3887024 Heat Riser Valve 1967 327/300hp

I removed the butterfly plate from the heat riser.