Zoomzoooie
Well-Known Member
My engine is a Teldyne 4a084 84CI engine that came with a Tillotson HR 181a 041 carb which has a 1 1/4" bore and also has idle and High speed adjusting needles and a built in pulse pump. Apparently this carb is good for up to 25 CI per cylinder. My engine falls in at 21 CI per cylinder.
I've been doing some research on possible carbs and I wanted to run a carb with mixture control or constant velocity. Since pretty all CV carbs are too high and might cause clearance issues with a cowl, I took a look at the Tillotson again.
I was thinking since it has a high speed adjustment needle, I started wondering if the high speed needle could also be used as a manual mixture control.
One thought was to attach at cable to the needle which could be "dialed" from the cabin, but the mag is right in the way. The only way around this would be if the carb can be run with the pulse pump at the top. Can it run this way?
I picture another way with a first outer sleeve which the needle would seat into, the same as it would in the carb body. The outside of the sleeve would have a threaded pitch course enough to move the needle an appropriate amount and have a lever arm on it. There would be a second sleeve which would thread into the carb body and would have the course pitch for the first sleeve to rotate on the inside. In effect rotating the first sleeve would move it and the needle in and out to adjust the mixture. The only problem is there less than 1/2" diameter of the needle housing in the carb and the 1/8" diameter of the adjusting needle threads to work between.
I'm also wondering if the pulse pump should or could be used in conjunction with the engine fuel pump and high wing tanks.
From what I see from photos and diagrams and my actual carb, there is a small chamber after the high speed needle before it goes into the venturi. I would guess it's about 1cc in size. I can't say for sure without tanking the welch plugs out, but I'm not about to do that since the carb was rebuilt when I got it. I have removed the pulse pump to investigate how it all works though. From what I can see there could be possibility the high speed needle could be used for manual mixture control.
I attached a pic of what the carb looks like where you can see the adjusting needles. The second pic shows more or less what the inside looks like and the pathways. The third pic shows how and where the carb is mounted to the stock intake.
So all that said, my question is will the high speed adjusting needle also work as a manual mixture control?
I've been doing some research on possible carbs and I wanted to run a carb with mixture control or constant velocity. Since pretty all CV carbs are too high and might cause clearance issues with a cowl, I took a look at the Tillotson again.
I was thinking since it has a high speed adjustment needle, I started wondering if the high speed needle could also be used as a manual mixture control.
One thought was to attach at cable to the needle which could be "dialed" from the cabin, but the mag is right in the way. The only way around this would be if the carb can be run with the pulse pump at the top. Can it run this way?
I picture another way with a first outer sleeve which the needle would seat into, the same as it would in the carb body. The outside of the sleeve would have a threaded pitch course enough to move the needle an appropriate amount and have a lever arm on it. There would be a second sleeve which would thread into the carb body and would have the course pitch for the first sleeve to rotate on the inside. In effect rotating the first sleeve would move it and the needle in and out to adjust the mixture. The only problem is there less than 1/2" diameter of the needle housing in the carb and the 1/8" diameter of the adjusting needle threads to work between.
I'm also wondering if the pulse pump should or could be used in conjunction with the engine fuel pump and high wing tanks.
From what I see from photos and diagrams and my actual carb, there is a small chamber after the high speed needle before it goes into the venturi. I would guess it's about 1cc in size. I can't say for sure without tanking the welch plugs out, but I'm not about to do that since the carb was rebuilt when I got it. I have removed the pulse pump to investigate how it all works though. From what I can see there could be possibility the high speed needle could be used for manual mixture control.
I attached a pic of what the carb looks like where you can see the adjusting needles. The second pic shows more or less what the inside looks like and the pathways. The third pic shows how and where the carb is mounted to the stock intake.
So all that said, my question is will the high speed adjusting needle also work as a manual mixture control?
