Air Intake Tube - Fuel Injection

[Larry M.]

Reading old posts there was discussion about the "fresh air intake tube", painted or not, with a mounting bracket or not, etc.etc. This was on a 63 car but some of the responses came from guys with 64 cars. So I looked and I have one from the left exhaust manifold with a mounting bracket to a rubber hose to a steel hose to the air horn on the air meter. The AIM calls it an air intake tube. But what is it for? The air meter is already pulling hot exhaust gas through the choke housing (I think) and the air horn has plenty of air supply from the air cleaner. So why is also pulling hot gas from the manifold directly with a second tube? Could this be to get it outside the throttle plate for idle? And if so, why?

The next time I start the car I'm going to feel it and see how hot it gets because I was surprised at the rubber hose.

[Dan H.]

Re: Air Intake Tube - Fuel Injection

Larry, the tube provides 'clean air' to the choke tube which has a suction from the choke housing on the air meter. The clean air tube isn't sucking air, it's providing it to the choke vacuum side. I went through a dust storm once, and REALLY apreciated the filtered air that saved my choke from becoming frozen with crud!

[Larry M.]

Re: Air Intake Tube - Fuel Injection

Dan, I don't understand the terminology. Of course, I understand (I think) that the choke has it's own tube going to the exhaust manifold and have always thought that vacuumn pulled exhaust gas through this tube and the choke and into the air meter which then is sucked into the engine. So this would be the same exhaust gas the second/separate air intake tube is pulling into the air meter. So what do you mean by "choke tube" above. Any air on the choke vacuum would otherwise come through the air filter so where would the dust storm get in?

[Dan H.]

Re: Air Intake Tube - Fuel Injection

Dan, I don't understand the terminology. Of course, I understand (I think) that the choke has it's own tube going to the exhaust manifold and have always thought that vacuumn pulled exhaust gas through this tube and the choke and into the air meter which then is sucked into the engine. So this would be the same exhaust gas the second/separate air intake tube is pulling into the air meter. So what do you mean by "choke tube" above. Any air on the choke vacuum would otherwise come through the air filter so where would the dust storm get in?

The upper choke tube going to the choke housing is inserted into a tube inside the exhaust manifold which goes into the top and comes out the bottom of the manifold, it is sealed. No exhaust gas is sucked up by the chokes vacuum, only hot air which is heated by the exhaust gas. If you left off the bottom clean air tube, you'd be sucking dirty outside air, like dust etc. It provides the clean air for your choke.

[Larry M.]

Re: Air Intake Tube - Fuel Injection

Got it....so the air intake tube is acutally taking air from the air horn to feed the choke tube to be heated, which explains why the rubber hose is ok. Thank you a lot. Next time I'm under the car I'll look up to see how the two tubes are connected.

[Alan D.]

Re: Air Intake Tube - Fuel Injection

Here is what Dan mentions

[John D.]

Re: Air Intake Tube - Fuel Injection

Nice pic Alan. Not enough FI car owners,etc replace the tube. It rusts out and then the choke housing is packed full of soot.

[John H.]

Re: Air Intake Tube - Fuel Injection

Got it....so the air intake tube is acutally taking air from the air horn to feed the choke tube to be heated, which explains why the rubber hose is ok. Thank you a lot. Next time I'm under the car I'll look up to see how the two tubes are connected.

Larry -

Here's that connection at the manifold outlet where the filtered air inlet tube joins the bottom end of the stainless tube that runs through the exhaust manifold.


ChokeTubeBottom.jpg

[Larry M.]

Re: Air Intake Tube - Fuel Injection

John, thanks a lot. I think what you are showing is the right hand side of a carbureator car (heat riser valve) but the principle is the same. I've got this one cemented in my knowledge base. I "sort of" remember this from a 250 horse car I once had but not sure, and I think I replaced the tube in the manifold.