Hey, so I just got a '79 F250 with a 351and I'm having trouble finding a couple of pieces for the air cleaner. I'm pretty new at it and I wonder if I'm looking for the wrong thing. Seems the door in the snorkle part (I don't know the proper name, sorry!) doesn't move when I start the truck. Now, is there a sensor in that top part? Is that the problem? Is there an aftermarket solution that bypasses this operation all together? The way I understand it is this door is supposed to close during starting to allow warm air from the engine into the carb and then open after idling to allow cool air in to regulate the temp. Feels like it's running pretty lean at all times. Thanks for helping a novice!

 

Hey there mbaroz, that thing should be operated by a vacuum line if I'm not mistaken. Should be a little canister attached to the top of the snorkle with a nipple on it, is there?

If it's there try applying manifold vacuum to it and see if it opens/closes or whatever and if that opens it up, just leave it on vacuum all the time. Otherwise you could just rip the door out of there somehow or jam it open. Might be other types that I'm not familiar with too.

 

Yeah, there is a little canister with a hose attached to it. Uhm, sorry again for not having at least a basic knowledge of this stuff...but how do I apply vacuum to it and it'd be okay just to have that door open at all times? It is open as the default. I was thinking this is why it has such a rough time starting. I adjusted the choke and this seemed to help a little...

 

That's a different story then, I thought it should've been open by default. I don't think you really need it, I think it's more about getting the engine warm for emissions reasons than for anything else. I'd be willing to bet the majority of folks on this site don't have it hooked to anything.

Is there a heater pipe coming up into the bottom of the snorkle? (right under the flap) Sort of looks like an aluminum foil tube. If the tube isn't there then you're not getting any heat from the manifold anyway.

Oh, and since it's open you don't want to put manifold vacuum to it anyway, it'll just close it all the time and choke the engine. I think originally it hooked up to a temperature sensor on the engine that opened the door up when the engine reached a minimun temp.

I'm hoping someone else can chime in and give you better advice, I can do a lot of this stuff, just not good at putting it into words.

 

The vacuum line should go to a ported vacuum switch that will open the door once warm. Probably the PVS on the thermostat housing. Lots of POs remove them for some reason. I like the trucks running as designed. You dont HAVE to have any of this tho and many many run very well without it with simply an aftermarket air cleaner.

Sorry but i dont have a chart to share with you but they are the forum somewhere.

 

The ported vacuum switch in the picture is not part of the mechanism in question.

This mechanism is called a hot-air intake system. Its purpose is to draw in warm air wafted from the exhaust manifold surface while the engine warms up. This is to prevent the carburetor from icing over. It has nothing to do with emissions, as previously stated.

It has two vacuum-operated parts:

(1) The vacuum motor on the end of the air cleaner snorkel. It is responsible for opening and closing the blend door at the end of the air cleaner snorkel. When open, air moves right past. When closed, air is pulled from the opening in the bottom of the snorkel, which is supposed to be connected to a tube that draws air from a heat riser on the passenger-side exhaust manifold. With no vacuum applied, the door should be open, meaning the door is parallel with the snorkel body and outside air can move past. With vacuum applied, the door should be closed and air flow is sourced from the heat riser. If the vacuum motor fails (which is common over time), the door should be stuck open. The vacuum motor is spring-loaded, and forces the door to the open position unless a vacuum signal forces it otherwise.

(2) The temperature sensor. This is a two-port device seated within the air cleaner itself. It is inside the air filter compartment and switches vacuum based on ambient temperature. One side connects to the vacuum motor (through a vacuum line underneath the air cleaner); the other side connects to a manifold vacuum source.

 

Thanks for the input...The snorkel is connected to the manifold via the foil tubing. I tried to locally find a replacement for the sensor on the cleaner, but couldn't...If all of this assembly has nothing to do with emissions, could I just scrap it all together? If I do, what becomes of the hose that comes from the manifold? And I guess I need a different oil filler cap because there's also a hose from that leading to that sensor...Thanks again you guys

 

You should not remove the P C V valve if that was on you list to remove. Some of them ,like my 460 is in the top of that oil fill cap. With another hose comming out of the other valve cover to the air cleaner. Yours could be just the oposite of how mine is connected. Just don't do away with the system.

 

Here is the illustration from the Ford master parts manual. The part that opens the flapper door is basic p/n 9D612.
Click on the .pdf link to view.
Vacuum Motor Assy (carburetor air cleaner)
Fits 77-up F100-350 w/ 351M400
D7TZ-9D612-B

Dennis Carpenter has 3 (704) 786-6139
Green Sales has 5 (800) 543-4959
Parts International has 3 (888) 727-0418
Miller Obsolete Parts has 1 (607) 722-5371
Collectors Auto Supply has 22 (800)414-4462

 

thanks mike0O0O0O!

 

Great...So, I won't junk the system but def need to get the motor that opens/closes that door..
Thanks so much!

 

I need the temp sensor described above. I cant find one anywhere. Any leads out there?

 

If it's for the same vehicle (79 F250/351M)
Sensor assy., carb air cleaner temp. control
D3ZZ-9E607-A

Dennis Carpenter Obsolete, Concord, NC has 2 (704) 786-8139
JST Automotive, Lebanon, TN has 2 (615) 443-3086
Wesley Obsolete Parts, Liberty, KY has 2 (606) 787-5293
Perogie Enetrprises, Highstown, NJ has 1 (609) 448-5593
Antique Auto Arlington, Arlington, TX has 1 (817) 275-2381
NOS Parts Source, Olathe, KS has 1 (913) 220-5746