I removed the exhaust control valve on my 300 1 brl carb engine due to stuck in open pos ( lack of lubrication),
the question is: would the engine perform normally?!!! or what effects does that have on the engine?. Thank you
Hamid.

 

Got another name for Exhaust Control Valve?

 

Hi Srercrcr

That's what its called in the shop manual, it is in the exhaust manifold used to heat up the fuel when warming the engine.
I dont see it has any impertance in the warm places like where I live in the west coast of Saudia Arabia.

 

I'm with you now. I believe that's also called a heat riser valve.
I believe when the engine is stone cold, the valve is somewhat closed, retaining newly warm exhaust in the manifold and I believe some is diverted up to the carb to prevent icing of the fuel in the venturi. I don't see any problem in that neck of the woods.

 

The previous explination is correct, carb icing can happen at around 40 degs. That was its purpose. Will you have probelms you will know when you start out and the engine dies at the first couple stops.

 

Kotzy:

You mean that removal of the exhaust valve will result in engines dies or quit, I experienced now that after I removed the exaust control valve the engine will not start easly when hot.
Please correct that.

 

When the engine is hot the heat riser valve is usually wide open, so your hot start problems are most likely not related to the removal of the valve. You may have a leaking carburetor that is dripping gas into the engine when it is hot and not running and causing hot start problems or a fuel pump that has low fuel pressure. Hot start is most likely a fuel related problem. In your part of the world unless you have really cold days/nights the heat riser valve is probably not needed , I have had some cars where the thing was stuck open and had no problems even in the north east USA. By the way --NICE TRUCK.

stractor

 

Stractor:

Thanks, you left me no doubt of that valve and its affect on the carb. Thank you olso for your impression on my truck.

Hot start is another subject, I ran an 84 1bbl Carter carb on my 66 Ford F100, straight six 300 engine, I only have this problem when engine is hard to start when hot, sometime it quits, I had to do several crancks before it gets going.

 

None of us can crawl in there when its running and see what gives, but think of this possibility. The flap valve when the engine is cold stands straight up and down directing a portion of the ehaust to go up and under the carb base. When it is hot it lays horizontal and some gases still get around the flap as it cannot be made to fit real tight however most are directed away. If we remove the valve the hot gases can freely get into that part of the casting and raise the temperature of the carb base. The result would be perculation of the fuel and the flooding of the hot engine. What I am saying is that you have lost the needed heating of the carb base in a cold engine and flooded the same area with heat on a hot engine, both result in drivability problems.

 

kotzy--you make a good case and it makes sense. I took a look at an early ford exhaust manifold picture and now I see how the Ford 6 heat riser works. I based my answer on heat risers that are closed when cold and direct exhaust through a passage in the intake manifold (most V8's). In the case of the 300 it seems that open allows exhaust to heat the intake and closed blocks off the exhaust from contacting the base of the intake manifold. Without the valve the manifold is hot all the time and could possibly cause vapor lock if the carb got hot enough. You could possibly put a plate (stainless) between the intake and exhaust manifold to block the exhaust from reaching the bottom of the intake manifold or repair/replace the heat riser valve, it is available at Rockauto.com

stractor

1966 FORD F-100 PICKUP 3.9L 240cid L6 : Exhaust : Exhaust Manifold Heat Riser

Item Price Core Total
ATP Part # 105022 {Heat Risers}
* Non-stock item--shipping delayed up to 2 business days *

$72.79 $0.00 $72.79

 

hmmm, I see now why my truck wont srtart easly when hot, replacing the exhaust valve is alowsy job due to:
1- That heavy combined manifold had to be removed.
2- some machine work have to be done.

I am going to put a new valve, it does worth it if the engine will not cause that hard starting, Thanks you all for this guidanc.
Hamid.