1947 plymouth P 15 heat riser

[larryconnors]

I have a stuck heat riser. How can I tell if it's stuck open, closed or somewhere in between? I soaked it with Free All and I plan to soak it again tomorrow and then force it until I hear the first cracking noise and the soak it again. Does this sound like a reasonable plan?

[Rusty O'Toole]

There is a special lube for heat riser valves. If you use penetrating oil be sure you lube with graphite when you get it moving, or it will freeze up again when the oil burns to carbon.

Try some penetrating oil or heat riser lube and tap tap tap gently with a small hammer. Not hard enough to bend or peen anything. You want to set up a vibration and get things moving. If you can get it to budge a little bit work it back and forth, back and forth until it comes free.

[larryconnors]

I followed your instructions and also resisted the temptation to use a bigger hammer. The heat riser now turns easily by hand but not quite easily enough for the spring to work it. If I turn the counterweight clockwise, it hits the post that the spring is mounted on with a stop. That must be the cold closed position. When it is warmed up, I expect the counterweight hangs straight down which is the open position. This one was stuck with counterweight turned counterclockwise to about the position of the stop if it had been turned clockwise. I suspect this is also a closed position. Unfortunately, I think the car was run with it like this and a three inch vertical crack now appears in the intake manifold below where the carb mounts. Since the engine seems to be running Ok with the crack I think I'll try to patch it. Any suggestions on how to do it?

[larryconnors]

Where would I get heat riser lube?

[Niel Hoback]

Try JBWeld if the manifold isn't leaking air. If it works, and I think it will, great. If not, you can chip it off and try something else.

[greg g]

to see if the crack is leaking, start the car and let it idle, when it gets up to temp, use an unlit propane torch slightly opened and pointed at the crack, if the idle speed picks up or he engine smooths out this would be a sign that the gas is being sucked through the casting. Clean up the area with a wire brush and give the JB weld or some of the 2 part marine epoxies a shot. The problem with that area and manifold repairs in general is they go through a lot of expanding and contracting due to heat cycles which teds to make any repair temporary.

[Niel Hoback]

Drill an !/8" diameter hole at each end of the crack to stop it from spreading. You can tap the holes and run a screw in them.

[larryconnors]

I got my clockwise and counter clockwise mixed up. Turning the counterweight clockwise results in the stop hitting the post that holds the spring. If the spring is too weak to work the counterweight can I put an extra turn on it or shorten it to make it stronger?

[greg g]

The spring is a bi metalic unit that contracts to move the riser when it heats up. The relaxed position (directing exhaust to the intake) the fully clockwise position directs the exhaust out without entering the intake chamber.

[larryconnors]

I'm back to basics on this. It turns out that all I did was to get the counter weight moving where it clamps on and the shaft into the manifold never moved at all. Now I'm spraying penetrating oil on the stud and I plan to use visegrips to try to get it to turn. Also I really don't know if the baffle is open or closed. Has anyone had success with this method?

[greg g]

fully clockwise closes the flow to the intake.

[Desotodav]

I am just doing some research on the manifold intake valve as I recently found a small hole in the heat box of my intake manifold. I noticed exhaust leaking from the heat box whilst the engine was warm the other day - I believe that this would indicate that the valve is directing exhaust into the heat box when the engine is warm. My counterweight rests in the most clockwise position when the truck is cold - is that the correct position?

Desotodav

[greg g]

the shaft must turn with the counter weight. The assembly fully clockwise allows the exhaust to flow with out entering the intake chamber.

[Desotodav]

Thanks for the reply Greg. I dug out a few of my manuals and did some reading. It would appear that there is a simple explanation for my troubles - my thermostatic coil spring appears to have been installed in reverse when the motor was rebuilt some time ago. Hence, the heat valve actually works in reverse - the counterweight rests in the open position when the engine is cold and opens up when the engine warms up. A simple fix (for a change) it would appear!

Desotodav