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Bronco Aircleaner

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Megiddo

Bronco Aircleaner

I found this air cleaner on a Bronco at the junk yard

I looks like it has a vacuum operated door on the back inside that "scoop", but the vacuum motor doesn't work.
Is that door supposed to open at low vacuum (WOT) for extra airflow? If so, does anyone know where to find a new vacuum motor?

1984 F250 4x4 351W ZF5-42

Gary Lewis

Re: Bronco Aircleaner

Administrator

I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm.

Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

85lebaront2

Re: Bronco Aircleaner

Administrator

Gary, Jim has Darth's old air cleaner so he should have a picture. Here is what it looked like installed:

The heated air motor is closer to the main body on Darth's, maybe it was for a 351 HO model.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Rusty_S85

Re: Bronco Aircleaner

In reply to this post by Gary Lewis

Gary Lewis wrote

I think that is an air cleaner off a 460 as they had a back door like that. But I don't know for sure as I don't have one of those air cleaners. Perhaps someone that does can confirm.

Anyway, I can't find in the master parts catalog a number for that vacuum motor. However, there is probably a number on it, so if you drill the rivets and pull it out I'll bet we can figure it out.

Ive seen that aircleaner listed on ebay as a 351HO and a 460 aircleaner. I dont know what it came on but I believe that vacuum closes the door because every photo Ive seen on ebay shows the door wide open without vacuum. I suspect with manifold vacuum it closes and only opens up under heavy load acceleration to allow for more air to be pulled in.

"Old Blue" - '56 Fairlane Town Sedan - 292-4V, Ford-O-Matic transmission, 3.22:1
'63 Belair 2dr sdn - 283-4V, Powerglide transmission, 4.56:1
'78 Cougar XR7 - 351-2V, FMX transmission, 2.75:1 9inch
"Bruno" - '82 F150 Flareside - 302-2V, C6 transmission, 2.75:1 9inch, 31x10.50-15 BFG KO2

Gary Lewis

Re: Bronco Aircleaner

Administrator

The 351HO base is different from the 460 base as the 351HO didn't have the opening on the back. And yes, vacuum closes the opening and it pops open below some value that the 460 apparently goes below at WOT.

Gary, AKA "Gary fellow": Profile

Rusty_S85

Re: Bronco Aircleaner

Gary Lewis wrote

The 351HO base is different from the 460 base as the 351HO didn't have the opening on the back. And yes, vacuum closes the opening and it pops open below some value that the 460 apparently goes below at WOT.

Thats what I figure but I know a lot of junkyards on fb list that style air cleaner as coming off a 351 truck and they call it a 351HO air cleaner.

I personally wouldnt use it as I would want the air to be cool air out from under the hood and that duct on the back side negates the purpose. Might as well run a open element air cleaner if you are going to have that.

I myself am still looking at air cleaners but probably will just use silver solder and fix the split aluminum base of my original one and restore it and just use it. I cant justify spending $250+ for a used OE air cleaner

Megiddo

Re: Bronco Aircleaner

I think, if the vacuum motor was working, that door and the hot air would only come in at or near WOT. So would more warm air be better than less cool air? Does a 351 need more airflow than can come through the snorkel at full throttle? I rarely see anything over 4000 rpm. I guess the limiting factor on air for the motor is the carb. I have a plain 4 barrel Holley at 600cfm. I know the stock 2v carb was something like 480 cfm. I'm not sure what you big motor guys have, but I don't think I've seen a truck with a double snorkel cleaner.

1984 F250 4x4 351W ZF5-42

ArdWrknTrk

Re: Bronco Aircleaner

Administrator

In reply to this post by Megiddo

I hadn't been able to find a vacuum motor.
Fortunately Bill Vose offered me his housing when he switched Darth over to EFI.

The engine vacuum travels through a green modulator which was located in that indexed hole in the foreground of your photo.
This keeps the door from snapping open (or shut) if someone takes a stab at the gas pedal.

I now have a 750cfm carb but vacuum secondaries keep manifold vacuum levels reasonable.
I'm not sure how much vacuum is required to overcome the spring inside the unit.
I wouldn't recommend a mechanical secondary carb on something as heavy as a pickup.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Bronco Aircleaner

Administrator

In reply to this post by Megiddo

I think more warm air is better than less cold air, and apparently Ford did as well since they put that air cleaner on the 460's.

But be careful of comparing 2bbl vs 4bbl carbs via the CFM ratings. The two carbs were flow tested at two different vacuum ratings, as explained on this page, and quoted here. Or, read a different explanation at The Carburetor Shop.

The cubic free per minute, CFM, rating for 2 BBL and 4 BBL carburetors can not be directly compared. 2 BBL carburetors (and 1 BBLs) are tested with a 3 inch vacuum while 4 BBLS are tested with a 1.5 inch vacuum. .... If you want to compare the CFM rating of a 2 BBL to that of a 4 BBL multiply the 2 BBL rating by 0.707.

And Wikipedia says the 2150's used on the 351's in these trucks were rated at, oddly enough, 351 CFM. Multiplied by .707 that says those carbs compare to a 248 CFM 4bbl.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Bronco Aircleaner

Administrator

In reply to this post by Megiddo

Oh, I forgot the dual-snorkel bit. I pretty sure that no truck came with one, although a few of us have created them. I used a 351HO air cleaner, which has a larger steel base than the aluminum ones most trucks got, and grafted on a 2nd snorkel.

But others have adopted the dual-snorkel air cleaner from an HO Mustang. Rick/Lariat 85 explained what he did in a series of posts here.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Bronco Aircleaner

Administrator

In reply to this post by Gary Lewis

Gary Lewis wrote

I think more warm air is better than less cold air, and apparently Ford did as well since they put that air cleaner on the 460's

We also have to consider the inlet air temperature that Ford designed their emissions systems around.
I forget the number exactly, but seem to recall that the thermostatic vacuum control inside the air cleaner is calibrated around 105° F.

I know underhood temperatures can get much higher than that, but I also expect the truck is moving right along if the throttle wide open for long enough that the 'vent flap' is actuated.
Many places might see ambient summer temps in excess of (105) whatever the calibration temp actually is.

In the other discussion about fans and shrouds it is pointed out that at highway speed the fan isn't doing much in 'pulling' air through the radiator.
This seems (to me) to suggest that the temp delta in front/behind the radiator is less. At least less enough to begin to unlock the fan clutch.
I'm not sure what the underhood temps compared to ambient are at highway speed. Or how high the in-snorkel temps are compared to ambient given the black uninsulated stock system.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Bronco Aircleaner

Administrator

Yes, 105F was the target temp for most of the trucks, as shown below, but there were others.

As for the true inlet temp, we have a link to the Carburetor Facts And Correcting Myths page on the Way Back Machine and that guy said:

Back in 1974 on my 1969 429 Galaxie 500 I installed an electric temperature gauge and several sending units: one into the air cleaner in the air stream, one just sticking out into the air by the air cleaner inlet, and another near the front grill. I used a rotary switch to flip between the sending units. Under the hood temperature on a hot day with the AC running was almost always over 200 degrees and in traffic was usually over 240 degrees. The temperature of the air inside the air cleaner was the same. Grill air temperature was never over 105. I installed a 3 inch diameter air duct from the grill to the air cleaner snorkel and was able to drop the air temperature in the air cleaner to a maximum of 175 degrees at 25 MPH in traffic and down to 120 degrees on the highway. The result was a better acceleration. Note: this was in Omaha, NE and I had to disconnect the cold air duct in the winter.

I didn't check on Big Blue when he was carbureted, but with the EFI I'm seeing essentially ambient temp at the air cleaner due to the insulation. But that air cleaner is on the fender and I don't know what temp air is actually getting to the throttle body and it is certainly higher as I don't have those hoses insulated yet - and they are very black.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Bronco Aircleaner

Administrator

Well 105(set) to 120° at highway speed, where heavy acceleration is likely to happen long enough to actuate the system doesn't seem too bad.
But the more likely scenario is being loaded on a long grade, where speed is not going to be so high.

It certainly adds a bunch of complexity!

There had to be good enough reason on the 460 for Ford to devote engineers time and manufacturing resources.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Bronco Aircleaner

Administrator

Yep, to all of the above. And I think the "good enough reason" is that the 460 can draw more air than the single snorkel wants to provide, which probably leans the mix - at just the wrong time. But, introducing such warm air also leans the mix, so they must have jetted the secondaries rich.

It certainly does add a bunch of complexity as to meet emissions they had to hold the AFR pretty close, which meant they had to hold the inlet air temp pretty close - with carbs and mechanical flappers. So much easier with a computer and EFI.

EDIT: No, warm air enrichens the mix!

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Bronco Aircleaner

Administrator

Yes, warm air is less dense and the same as altitude compensation the fuel needs to be reduced.

But I would think a restrictive intake snorkel is going to richen the ratio, just like a choke does.
More vacuum at the boosters (which are above the throttle plate) is going to suck more fuel out of the bowl(s), through the jets.

It's certainly much easier to control pulse width at the injectors than to get a carburetor to respond properly to a wide range of demand and conditions.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Bronco Aircleaner

Administrator

Yes, I guess you are right about the snorkel enrichening the mix. The choke is a good analogy.

Gary, AKA "Gary fellow": Profile

Megiddo

Re: Bronco Aircleaner

Well, Ive got the aircleaner now. I may as well try to clean it up and see if I can get it working. Its a job I'll probably save for a bad weather day if I can ever carve down the "honey-do" list. Thanks for all the input and ideas.

1984 F250 4x4 351W ZF5-42