Heat Control Valve - result if missing?

[thovis]

My project didn't have the heat control valve when I purchased it. I had the engine rebuilt and started it up last weekend, and appeared to run well.

What is the result if this is missing? I assume that the shaft will still turn on its own right?

Here is a picture from Tony Norton's post in 1993.


Thanks in advance
Tom

[Herb Tate]

My jeep has one but it wasn't working. When the engine got hot it would overheat the carb and put put put and run rough. When I tack welded the flap back in place on the shaft the putting almost totaly quit. It will put every once in a while. I can live with that. That was the one of the best repairs that I made to the engine.

[Tony Norton]

Tom:

A couple of things. If there is no counterweight and the shaft is there, chances are the diverter valve is there because it is welded to the shaft. Without the counterweight and temperature control spring, the diverter will float to whatever position it is confortable at. This will most likely be closed position which will divert hot exhaust gases up and around the intake manifold. This will have the effect of causing stalling when the engine is hot, reduced fuel mileage, and hard starts in the summer. During winter operation, engine operation MAY appear to be unaffected.

If you have the shaft there with the slot in the end and it is free, all you have to do is install the spring stop, temperature control spring, washer, and counterweight. Just make sure the shaft is rotated fully clockwise as this is the closed position of the diverter valve. The short leaf of the temperature control spring is placed in the slot on the shaft, and the long leaf of the spring rests on top of the stop.

If the shaft is binding up, I recommend that you replace the shaft, the bearings, and the diverter valve, as well as install the missing parts. It is fairly easy to do, but you will need a die grinder and a welder to remove and replace the diverter valve.

[thovis]

Hi Tony,

Thanks for the explanation, I just ordered the parts from Brent Mullins (Ron didn't have in stock). Also, will this cause some pops in the Carb? I got that when I came to idle (with the first start).

Here is what I have.

[iowa]

looks a little like mine.
mine was frozen in this position.
i just left it
and plan to fix it this winter.
but...it runs great.
i forget just what position it is frozen in
dave

[Tony Norton]

Dave: From the orientation of the slot in the diverter valve shaft, it looks like your valve is stuck in the closed position. In this position, you are heating the intake air all the time.

Tom: Yes, a malfunctioning heat control valve can cause the popping you mention. The thick diffuser gasket at the base of the carburetor serves two purposes. One is to break up and diffuse the gasoline throughout the intake manifold. The second purpose is to insulate the carburetor from the heat bildup on the manifold metal. Heating the carburetor itself would tend to cause vapor lock.

Excuse the crude diagrams, but I hope they help explain how the Heat Control Valve (Heat Riser) works.


Figure 1. Heat Control Valve in the CLOSED position.


Figure 2. Heat Control Valve in the OPEN position.

Since I changed my ISP host the photos that some of you linked to don't work anymore. Here is the photo that Tom has linked to in his post above.

[Ben Hovis]

Tony,
Mine is installed with the arm facing the engine, or 180 degrees out or backwards. What is crazy is that I have been running it that way since 1979.

Guess it still works in that position.

Don't know why it was done that way.

Tom,
You are smoking on getting the "General" done.

Dad

[thovis]

Tony that is just fabulous!!! Thank you so much for taking the time.

Tom

[simmo]

Good post here but i have a question also Is the spring in IOWAS picture the wrong way round When fitting the spring should it coil clock wise when looking at it head on as Iowas does or should it coil anti clockwise when looking at it head on (Working from center of the spring outwards):?: When the spring heats up does it coil up or uncoil with the heat

[Tony Norton]

Good question Simmo. I did not put the spring in the original diagrams.

I have updated the diagrams to show the Bi-Metal Spring that reacts to the heat and the spring stop. Scroll up and take a look. The spring inner tab is placed in the Diverter Valve slot so that the spring wraps around the shaft in a clockwise direction with the long tab on the end of the spring lying on top of the Spring Stop.

When the spring heats up it will coil up (get tighter in a clockwise motion), but since the long end is held by the Spring Stop from the clockwise coiling motion, the other end will be forced to turn counterclockwise and force the shaft tab in a counterclockwise direction lifting the Counterweight and opening the Diverter Valve.

When the correct temperature is reached to cause the spring to start its movement, the transition from fully closed to fully open takes less than five seconds.

[simmo]

Thanks for posting that tony
Its cleared it up for me. I was working on my friends manifold today removing a broken exhaust stud & noticed his lever moving as i was directing heat onto the stud but i didnt make note of what way the spring was fitted. It only made me think when i read this post & thinking about it i think my jeeps spring is fitted the wrong way That could be the reason mine is a pig to start after ive driven it a while in the hot weather

[Tony Norton]

Mine is installed with the arm facing the engine, or 180 degrees out or backwards. What is crazy is that I have been running it that way since 1979.

Ben:

I suspect with the counterweight installed on the wrong side that you can lift it indicating that the valve is not stuck. Installed in this position the weight of the counterweight will keep the diverter valve open at all times. If the spring is on there it is trying to force the counterweight further down but the diverter valve is already open and lying against the manifold internal port edges. Unless you operate the jeep in really cold weather, it is better to have this valve stuck in the open rather than closed position as when the manifold temperature comes within the required values this valve will open and stay open until the manifold cools sufficiently. This will not occur until the engine has been shut off for a period of time. I think it takes more than 15-minutes to cool enough to close the valve.

A stuck open heat control valve used to cause lead fouling of the spark plugs, but since there is no more lead in fuel you will not see this problem anymore. Now, if you operate the jeep in cold climes, you will notice poor engine performance.

[iowa]

hi tony
thanks for the fabulous drawings!!!!
i really need to remedy this this winter.
if you remember
i also have a crack in one corner
so will do both this winter
but for now i'll enjoy driving it.
have a fair parade the first saturday in sept!!
thanks again tony
dave

[tsmgguy]

Tony, Thanks much for the great diagrams. Of course, the counter weight is easily visible. Is there a quick test that one can do with one finger to see if this set up is working properly? A wiggle test, as it were? Thanks again!

[Ben Hovis]

Tony,
Thanks for the additional information. Will see about installing it in the correct position. Your drawings are super.
Thanks again for all the assistance.
Ben