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Air Cleaner/Filter Questions

lomarker

Newbie
Joined
Nov 13, 2016
Messages
7
Hi -

Searched around a bit but couldn't find the answer. Leaking carburetor brought me to the engine compartment for a rebuild on what I believe to be the stock 2100. New to automobile carbs, but gonna give the rebuild a go.

Wanting to swap out the stock air filter assembly for a simple round unit. I don't have the hose or cold intake assembly. Brings me to hopefully a couple easy questions :

1. There is a hose connected to the rear of the stock unit that runs to some sort of can below the passenger side floor board - can't figure out what it is. The second hose coming from the can is blocked off. What is the can and what do I do with this hose if I go to a round unit?

2. There is a also a breather hose (I assume) from the stock assembly with a short hose that goes to the back of the block. Again, what do I do with this hose if I go to a round unit?

Thank you in advance. :)

I'll get some signature info in - but '74 with 302, NP435, NP205, 3" lift.
 
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gr8scott

Contributor
Bronco Guru
Joined
Jul 1, 2011
Messages
1,823
That can is the charcoal canister. Its part of the fuel tank venting/evap system. Its best to leave that system intact.

And welcome to the site!
 

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jckkys

Bronco Guru
Joined
Mar 15, 2012
Messages
5,196
The cheap cheesy after market air cleaners don't have several desirable features found on the OE types. It's the kind of thing you get to sell it to the uninformed. After all they are simple and shiny.
 
Joined
Jul 23, 2020
Messages
6
In response to your questions

1. This is the charcoal canister that is part of the evaporative control system. One end is connected to a vent on the tank, and the other as you already know to the air intake. Your engine will run fine without it, but it's better for the trees and bunnies and stuff if it's working to leave it hooked up. ;D

2 I believe you are referring to the hose connected to the rear port on the valve cover. If so yes this is a breather vent. I believe you can replace this with a breather without any trouble.
 

hatleyjm

Jr. Member
Joined
Jan 19, 2011
Messages
106
Just to add a bit more info that I found out when I was asking about my stock air cleaner housing:
The charcoal canister helps with fuel vapors that accumulate in the tank. When the fuel is vaporized, it makes its way up through a separator tank then on to the charcoal canister. The charcoal captures the unburned hydrocarbons then, when the vehicle is running, releases them into the air cleaner to be burned. Modern vehicles have similar system albeit more complex with a purge valve that opens and closes at the direction of the ECU. The point of the bronco's evaporations system is to prevent unburned hydrocarbons from entering the atmosphere. It doesn't not affect performance in any way. It makes it safer to park it indoors because raw gas fumes (the part of fuel that burns) is confined within the vehicle. There are fittings that you can use to reattach this part to an aftermarket air cleaner. In the photo below, it is part number 9D692--something like this that is modified to fit an aftermarket air cleaner would work.

As for the other question, the parts you are asking about are for the positive crankcase ventilation system. There's a certain way that they flow--one side (I believe the drivers valve cover) is where air enters the engine (filtered through the air filter). The passenger side valve cover is where the air exits. This hose should be hooked up to the plate on the bottom of the carburetor so that the fumes can be burned. there are aftermarket oil caps with filters on them in cases where the inlet side is separated from the air cleaner housing--pics below.

Websites for the pics:
http://www.garysgaragemahal.com/air-cleaner-housing-s.html
https://www.dennis-carpenter.com/br...ump/c5me-6766-a-oil-cap-chrome-twist-on-wfomo
 

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lomarker

lomarker

Newbie
Joined
Nov 13, 2016
Messages
7
Appreciate the replies and information. I think I'll keep the stock filter assembly as designed.
 

gr8scott

Contributor
Bronco Guru
Joined
Jul 1, 2011
Messages
1,823
There's a certain way that they flow--one side (I believe the drivers valve cover) is where air enters the engine (filtered through the air filter). The passenger side valve cover is where the air exits. This hose should be hooked up to the plate on the bottom of the carburetor so that the fumes can be burned. there are aftermarket oil caps with filters on them in cases where the inlet side is separated from the air cleaner housing--pics below.

No. The pcv valve is what's pulling air through the engine, via a vacuum source from the carburetor. It can be located in either
valve cover as long as the opposite valve cover has a source for clean air entering the engine.
 

hatleyjm

Jr. Member
Joined
Jan 19, 2011
Messages
106
No. The pcv valve is what's pulling air through the engine, via a vacuum source from the carburetor. It can be located in either
valve cover as long as the opposite valve cover has a source for clean air entering the engine.

OK I gotcha. Thanks for the clarification. It sounds like I had the airflow direction correct for the stock setup but was thinking of it as a "pushing air into the engine" setup instead of a "pull air into the engine" setup.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Not only can it be either location, but even Ford swapped them around from time to time to suit the rest of the engine accessories.
In basic form (not sure of any other changes) the '66 to sometime in '70 V8 engines had the valve in the passenger side and the clean-air return in the driver's side.
For '71 and probably all the way through '77 they changed that so that the valve and the vacuum were pulling from the driver's side cover in the oil fill cap. The short curved return air then went from the air cleaner housing to the passenger side rear.

And by the way, that second large port on the charcoal canister is not actually a cap. Well, it is a "cap" but it's not closed to outside air. It's an open vent that is protected from direct intrusion of water and debris into the canister. Sometime in late '72 they changed from just an open ended plastic support to keep the hose open, to the "mushroom cap" that we are more familiar with.

The system was first seen on the '70 model Broncos where the steel can was mounted on the frame rail and had a rock shield protector. That style continued through '75, where in '76 and '77 they changed to the more modern plastic canister and mounted it up high on the firewall.
But it remained with the same connections for all the steel ones. Smallest one to the fuel tank(s) through the condensing tank in the cab, medium sized one (starting in '73) to the float bowl vent on the carburetor, first large one had a hose running to the air cleaner and the second large one had a hose that just ran up into the engine compartment to keep it out of harm's (and water's) way.

At the same time the EVAP system was added, the gas caps were changed to non-vented and with a different latch design so you could not accidentally or on purpose change to the older vented style cap.

Paul
 
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