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Is there a vacuum hose going to that spring on the left side of the air cleaner? Does it open with the one on the right, ie, once it's warmed up?
The vacuum actuator on the long snorkel is controlled by the thermo switch in the air cleaner and opens when the engine warms up. The actuator in the short snorkel is fed by a tee before the thermo switch and only opens when manifold vacuum drops. This is exactly how the O.A.I. flapper door works.
The vacuum actuator on the long snorkel is controlled by the thermo switch in the air cleaner and opens when the engine warms up. The actuator in the short snorkel is fed by a tee before the thermo switch and only opens when manifold vacuum drops. This is exactly how the O.A.I. flapper door works.
I should have remembered that. That is also how the CCC air cleaner worked, which was newfangled option in 67, then came on everything in 68, I think.
For anyone wanting to know the 71 non-ram-air air cleaner letter code, it was "NH". I rememember this only because it's the same code the 84-85 VIN 9 307 dual snorkel air cleaners used. I got one in the shop but can't recall if it still has the label on it.
(And 69 H/O air cleaner code was "OW" for those that care).
@joe_padavano Did the code on the 1971 Non-OAI air cleaner change during the year?
The inspectors guide lists a different code: "ND".
And as another point of reference (non Oldsmobile) "Dr. Decal" lists the two different codes. Code ND for a build date BEFORE 05/06/1971 and Code NH for a build date AFTER 04/29/1971. Don't know where this info came from and why there's a gap.
@joe_padavano Did the code on the 1971 Non-OAI air cleaner change during the year?
The inspectors guide lists a different code: "ND".
And as another point of reference (non Oldsmobile) "Dr. Decal" lists the two different codes. Code ND for a build date BEFORE 05/06/1971 and Code NH for a build date AFTER 04/29/1971. Don't know where this info came from and why there's a gap.
The PIM shows Note E that documents a change to the part number for that air cleaner on 4/28/71, so yeah something changed.
The 1973 and 1975 parts manual lists two different air cleaners between 71 and 72 with the change occurring 4/28/71.
So more than likely ND would be 6486966 and NH is 6487337
I'll see if I can hunt down my latest 71 non-OAI air cleaner. It may still have the tag on it. Or it may not.
I wasn't aware of the split dates. Never paid that much attention. I just know the 71 I had a long time ago was built in May, and had an NH sticker on it. And when I picked up my new 85 442, it had an NH sticker on the front. I thought it was kinda odd, but in a neat way. I do know my 72 442 with a 350 MT came with the regular 4bbl air cleaner, single snorkel. Along with single exhaust. Which got fixed.
The 1973 and 1975 parts manual lists two different air cleaners between 71 and 72 with the change occurring 4/28/71.
So more than likely ND would be 6486966 and NH is 6487337
Originally Posted by joe_padavano
The revision on the engineering drawing was for the 1971 model year
I have this air cleaner on my Cutlass and the tee is currently installed after the thermo-switch. Both flaps are closed until the car warms up and then they both open. I bought it with old vacuum hoses intact and restored it as well. I'm struggling with the concept that the short snorkel is controlled by throttle like a ram air cleaner?? These flappers in the snorkels currently open with engine vacuum, not a vacuum drop?? Does anyone else have this air cleaner on their car? I'm interested in how it operates. This was a nice upgrade for my 350 powered car and you can feel a slight difference in midrange power (per the butt dyno.)
I don't recall how the 71 air cleaner is hooked up, but I can't see it being any different than the Thermac setup on the dual-snorkel VIN 9 307 air cleaners.
A line from the manifold vacuum source runs up to a Tee. It branches off two ways. One way goes to the shorty snorkel flapper and thus works directly with manifold vacuum. The other way goes to the temperature sensor in the air cleaner. On cold startup (less than 86 deg F), the temperature sensor's bimetallic vacuum pod bleed valve is shut, allowing full vacuum to the snorkel flap. It positions itself to close off the outside air and open up the stove pipe from the exhaust manifold to the bottom of the snorkel flapper. It draws air across the warmer exhaust manifolds to help heat incoming air. As the temperature sensor gets warmer, it starts to open the vacuum pod bleed and reduce some vacuum and the door goes to a varying spot as the vacuum is dimished to the flapper. So some air comes in from outside and some from the exhaust manifold. Eventually, (when it reaches 131 deg F) it cuts all the vacuum from the big snorkel flap and the exhaust side of the big snorkel flapper closes completely and the big snorkel outside inlet gets all the air. It will regulate if temps at the sensor are between 86 and 131 deg F.
As far as the short snorkel flapper, when vacuum is applied >4.5" Hg, the joker shuts. As vacuum drops to 1.5" Hg, the flapper opens accordingly. If you lose vacuum to the air cleaner, then both snorkels are open to "colder" air regardless.
Big snorkel flapper controlled by temperature sensor valve. Short snorkel flapper controlled by manifold vacuum only, without regard to temperature.
Thanks for sharing how the 307 vin 9 is set up. I was mistaken in my post. The flaps do actually close with vacuum applied. I'm still interested in further understanding of the 1971 442 set up. It seems weird that if you were driving the car when cold, that the second snorkel could open upon throttle and a vacuum drop and basically bypass the hot air provision?? I bought my air cleaner with intact vacuum lines and did not reroute anything. I'm probably just over thinking this as well.
It seems weird that if you were driving the car when cold, that the second snorkel could open upon throttle and a vacuum drop and basically bypass the hot air provision??
When you go to W.O.T. and manifold vacuum goes to zero, BOTH flappers open no matter what the temp switch is doing. All the temp switch does is allow the long snorkel to be open all the time once the engine is warm.
When you go to W.O.T. and manifold vacuum goes to zero, BOTH flappers open no matter what the temp switch is doing. All the temp switch does is allow the long snorkel to be open all the time once the engine is warm.
Because it cuts the vacuum off when at temp. No vacuum, means spring pushes it open regardless of cut off by switch or none in the first place.
I was going to ask, does anyone remember the actual effects of the CCC originated heat pipe air cleaner system, and then I remembered my old van has that stuff long disconnected (it was in Florida for 40 of its 51 years) and it takes forever to warm up. Plus, it's a manual choke now. Plus it's an Autolite 2 barrel. Plus it's a Ford.
