[Bentwheelbob]

I spent most of the day killing time under the hood of the Black Car cleaning stuff up and straightening a few things out. I am planning to swap air cleaners at least temporarily so that I can blast and repaint the one on the car now. I have a nice "new" one I did for the red Car that I will put on it for the time being. However, I am perplexed by the vacuum hose routing. I can find nothing in the service manual or restoration guide. The existing air cleaner was not connected to a vacuum source. The vacuum fitting on the front drivers side of the manifold is capped off and there is nothing connected to the air cleaner. It seems like the vacuum source should connect to one side of the air inlet sensor mounted in the air cleaner and that that other nipple on that sensor should then connect to the two vacuum diaphrams. However, the way the hoses are currently hooked up has both vacuum diaphrams hooked to separate nipples on the air intake sensor (see picture label #1) and then there is a "t" fitting on one of the hoses going to the vacuum diaphrams (see picture label #2). My assumption is that this was intended for a hose to connect to that "t" fitting that was then connected on the other end to the vacuum source. This would mean however that one of the air cleaner intake flappers would always be open and the other would open when the car warmed up. Can anyone provide a diagram or some direction?

I have attached a second picture that shows the replacement vacuum hose set up I bought from PY. It appears to be designed the way I think seems correct - both vacuum actuators hooked to one side of the air inlet sensor, but the separate hose that I think would go to a vacuum source and the other side of the sensor is only about 6" long and won't come close to reaching the intake nipple on the front drivers side.

Lastly, I have a picture of the breather tube that was on the Black Car and the repop piece I bought from PY for the Red Car. I refinished the repop piece with black manganese from Palmetto, while the original is just bare metal. Which is correct? What about the difference in shape?

[Formulabruce]

Bottom of RA air cleaner showing vacuum routing. T on far side and loop out to the vac flap
Yes this is a air cleaner for a 400, but 400 uses 2 vacuum flaps , same as the 455 unit.

[Bentwheelbob]

Bruce,

Thanks again. I think this is right....

Now what vacuum source is "correct" to connect to the other nipple on the air inlet switch? Is it the fitting in the manifold front, driver's side? That seems like a long run from the rear of the air cleaner. Also, what is the conventional wisdom between yellow stripe vacuum hose vs. white stripe? Did the factory use both?

[70RAlll]

Originally Posted by Bentwheelbob

Bruce,

Thanks again. I think this is right....

Now what vacuum source is "correct" to connect to the other nipple on the air inlet switch? Is it the fitting in the manifold front, driver's side? That seems like a long run from the rear of the air cleaner. Also, what is the conventional wisdom between yellow stripe vacuum hose vs. white stripe? Did the factory use both?

everything in this post appears correct to me. Vacuum to one side of the thermo valve, the other port supply's that vacuum to both snorkels when heated up.. I say it is exactly as you have it routed in these pictures.

[blue71ta]

Bob,
you actually had it right the first time. Here's a pic of my original 455 HO RA air cleaner with the original, white-striped hoses. The short one that comes off the tee in the front is the one that goes down to connect to the vacuum source on the intake manifold (the fitting that you have circled in your engine pic).

[Bentwheelbob]

Originally Posted by blue71ta

Bob,
you actually had it right the first time. Here's a pic of my original 455 HO RA air cleaner with the original, white-striped hoses. The short one that comes off the tee in the front is the one that goes down to connect to the vacuum source on the intake manifold (the fitting that you have circled in your engine pic).

If you plumb the vacuum lines like that, and like the black car was plumbed, one of the vacuum actuators will be closed at all times when the engine is running. These vacuum actuators are normally open, and close when vacuum is applied. That means that as soon as manifold vacuum is generated the actuator on the vacuum source side of the air inlet thermal vacuum sensor will close the flapper and as long as vacuum is present the flapper will remain closed and prevent fresh air from entering the engine. Also, the only way to get both vacuml actuators to work in unison is to have them both plumbed to the same side of the air inlet thermal vacuum sensor.

I need to do some more experimentation in the morning, but I think the air inlet sensor is normally open which lets the vacuum go through the "switch" so to speak thereby closing the flappers in both snorkles. Once the vehicle comes to operating temperature, the switch (air inlet sensor) closes thereby preventing the vacuum from passing through it and to the actuators. In the absence of vacuum, the flapper doors open and fresh air enters the combustion process.

This sounds good on paper and i think I am right.

[Pepi]

Originally Posted by Bentwheelbob

If you plumb the vacuum lines like that, and like the black car was plumbed, one of the vacuum actuators will be closed at all times when the engine is running.

That is what I was thinking.

[Bentwheelbob]

It sounds good on paper and I am completely wrong....

So after coming down from my post turkey and sweet potato high, and getting a good nights sleep., I broke out the heat gun and vacuum pump this morning. I was correct that the air inlet thermal vacuum sensor is normally closed, but both nipples on the bottom of the sensor are on the closed side. Pull a vacuum on one nipple of the sensor and it moves through the sensor and creates a vacuum on the other nipple as well. Put heat on the sensor and the sensor opens up on the top side of the sensor (that part on the interior of the air cleaner) and releases the vacuum. Once the vacuum releases it lets the flapper doors open. Those who said that the correct plumbing was as pictured below were correct.
I think...

BTW - the vacuum actuators on this air cleaner work perfect and hold vacuum, but show no sign of having been replaced unless NJSteve did his usual fine job.