[Pepi]

Originally Posted by Bentwheelbob

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.

So once it opens up, and lets the vacuum out, it is a controlled vacuum leak... Got it now. Never checked mine, I always thought it allowed vacuum when cold and closed when warmed up stopping vacuum to the actuator.

Still trying to locate where I found the colored hose information.

[Judge273]

Mine is as blue71ta shows, and was routed plus checked per Brews 72 silver HO verified by Dan Jensen at TA Nats.

This will be a good tread all by itself.

[blue71ta]

Originally Posted by Pepi

So once it opens up, and lets the vacuum out, it is a controlled vacuum leak... Got it now. Never checked mine, I always thought it allowed vacuum when cold and closed when warmed up stopping vacuum to the actuator.

Still trying to locate where I found the colored hose information.

You are correct. When it is cold (with the engine turned off), the doors are closed on the bottom side. When you start the engine, the vacuum causes them to open, which allows the pre-heated air to come in from the ducting. Once the engine is fully warmed up, the vacuum is cut off, thereby closing the flaps again and allowing only the cool, outside air to come in through the hood vents / rubber RA boots (on the top side).

The system is designed to aid in cold startup / engine warm-up. Most factory GM air cleaners use the same system, but would only have one vacuum pod on a single snorkel air cleaner...

[Pepi]

Originally Posted by blue71ta

You are correct. When it is cold (with the engine turned off), the doors are closed on the bottom side. When you start the engine, the vacuum causes them to open, which allows the pre-heated air to come in from the ducting. Once the engine is fully warmed up, the vacuum is cut off, thereby closing the flaps again and allowing only the cool, outside air to come in through the hood vents / rubber RA boots (on the top side).

The system is designed to aid in cold startup / engine warm-up. Most factory GM air cleaners use the same system, but would only have one vacuum pod on a single snorkel air cleaner...

I knew they closed upon startup to allow the heat to help warm up the engine, just never knew the sensor "leaked" vacuum to allow them to open back up. That just seems strange to have a vacuum leak like that right off the manifold, instead of a ported vacuum switch.

[njsteve]

And now you know why I leave those things disconnected. The less vacuum leaks, the better the car runs.

[johnta1]

I wouldn't really say it's a 'leak', unless you think the power brake vacuum line is a 'leak'?

[njsteve]

Originally Posted by johnta1

I wouldn't really say it's a 'leak', unless you think the power brake vacuum line is a 'leak'?

Correct on that point, but those flapper diaphragms tend to leak after 40 or so years, in addition to the little thermostatic valve that the hoses connect to in the air cleaner base.

[Pepi]

Originally Posted by johnta1

I wouldn't really say it's a 'leak', unless you think the power brake vacuum line is a 'leak'?

Correct, I didn't think that far ahead before I commented.

[Bentwheelbob]

So the air cleaner project is finished. I switched out air cleaners and am using one I restored previously. I'll go through the one I removed and ultimately reunite it with the Black Car. Thanks to a lot of assistance from the forum, I think I have it plumbed correctly. I know that it is working correctly. It's pretty cool to watch the flappers close up and then several minutes later reopen. I also have the new correct air cleaner decal in place, and of course PB's correct lid decal. Thanks to everyone for your assistance.

[Bentwheelbob]

Mission creep....

While I had the air cleaner off I decided to do a little engine clean up and detail. I have a lot of parts that were gathered for the stalled engine transplant on the Red Car, and these came in very handy. I switched out the TCS switch, installed Norwood's new repro heat riser parts, installed an NOS choke coil and cover, installed an NOS idle stop, switched out the throttle cable bracket, replaced the throttle return spring, installed a new brake booster vacuum hose, removed and repainted the valve covers, switched out the breather tube, and media blasted and repainted the a/c brackets. If I had planned better I could have added one of Greg's upper radiator hoses to the list, but I do have one coming from the next batch he makes. I had a very good starting point, but I am happy with the improvements. I'm sure I've missed a few things or have some items that are not correct and welcome all the help I can get. Here's a few before and after shots - regrettably I did not fire up the camera before removing the valve covers.

[70RAlll]

Originally Posted by Bentwheelbob

So the air cleaner project is finished. I switched out air cleaners and am using one I restored previously. I'll go through the one I removed and ultimately reunite it with the Black Car. Thanks to a lot of assistance from the forum, I think I have it plumbed correctly. I know that it is working correctly. It's pretty cool to watch the flappers close up and then several minutes later reopen. I also have the new correct air cleaner decal in place, and of course PB's correct lid decal. Thanks to everyone for your assistance.

You still have me lost on your setup.. one of your flappers ,using this plumbing, will always be exposed to vacuum. The thermo switch only has a chance to regulate one of the flappers with this plumbing. everyone can shoot me down on this, but I still think you have it wrong. I think the clips on the underside of the snorkel only hold the hoses to the flappers, the vacuum hose went directly from the intake manifold vacuum source to one of the ports on the thermo switch. I think you have gotten tied up with trying to make everything sit nice and neat under the snorkel, when it didn't. How does the thermo switch regulate the flapper that is right next to your "t"?? when the engine warms up, what is going to interrupt the flow of vacuum to the 1st flapper??nothing as I see it..
This is how I think the vacuum hoses ran:
1st Thermo Switch Port:vacuum directly from intake to one port of thermo switch
2nd Thermo Switch Port: other port of the thermo switch to the "t"
Both Flappers: "T" to each flapper.

That is the only way the thermo regulates both flappers.