I'm starting this thread so matthewq4b and I, as well as anyone else, can cuss and discuss air cleaners.

Matthew - You said the factory air cleaners are restrictive. Does that apply to all of them, including the HO version used on the 351HO and 460's? What about the dual snorkel ones used on the Mustangs?

I ask because I am/will be building a dual snorkel unit for Dad's truck, and have been planning to use one of the HO units as the base.

 

Restrictive is a relative term, Gary. Certainly, by going to the dual snorkles, your set-up will be less restrictive than original!

 

That's assuming the snorkels are the restriction. I'm wondering if the larger diameter, but shorter, HO-style units are more or less restrictive than the taller standard units.

 

I would think during all the factory's tweaking and road testing, it was all done with the factory aircleaner setup in place. Change one thing, it affects everything else.

 

Gary..I have a '52 Cadillac batwing on my 351 HO..

 

From the other thread;
I'm seeking to understand where the restriction is.

Also, I'm not sure I agree that "The factory air cleaner is not really designed to keep the inlet at a set temp it is designed to keep it from falling below a set temp." If that were the case they wouldn't have plumbed the snorkel to the radiator support to get cooler air than what was available under the hood. It looks to me like Ford went to a bit of trouble and cost to get the coolest air possible in order to keep the inlet air temp as stable as they could.

 

I replied in the "PCV" thread before I realized that you have this thread going too, but I disagree with some things that were said also.

In my experience messing with the door in the snorkel and the sensor that runs it, the sensor actually modulates the door, the door will actually be 1/2 open, 1/4 open, etc. That tells me they did have a target temp when they designed it. I forget what manual I was reading, but 100 degrees comes to mind as the target temp for some of these setups. Then they tried to tune the carb with that in mind.

There is more restriction in the stock aircleaner setup. It's a known fact that on the holley type carbs that use venturi vacuum to open the rear barrels, the rear barrels will open earlier with a stock aircleaner, they will open later with a open aircleaner. This came to light when people started running the open aircleaners and found they were having a hard time getting the carb to open up(probably on the stock 4bbl carbs). The more restrictive stock aircleaner affects the pressure delivered to the diaphragm on the secondaries.

 

The sensor temps are shown here: Air Cleaners - ???Gary's Garagemahal. Most I've seen are 105 degree.

 

Interesting discussion. Concerning the snorkel to the grill, does the ram air effect make any noticeable performance improvement? Perhaps the logic for the snorkel isn't solely for temperature, but to also take advantage of the free ram effect.

On some light airplanes, the carb intake is ducted in a similar fashion. This setup is known as a poor man's supercharger.

I also think there is some advantage to the "restrictive" snout on the stock air cleaner assembly. Even though it would seem to reduce overall airflow, it increases the velocity entering the carb. Years ago I remember reading about dyno testing different air cleaners on a VW bug. Trimming the snout reduced torque at low RPM, if I remember correctly. It was quite the interesting read, but there's no way to find it again.

FWIW, the factory air cleaner on my '66 Corvair has two long and very narrow snouts. This is on the performance 4x1bbl engine. No snorkels, so it's still drawing air from the engine compartment. There must have been some advantage to the restrictive snouts or Chevrolet would have opened them way up. Perhaps it's a trade off for increased low RPM torque versus extra power at the top end.

Respectfully submitted.

 

I don't *think* the standard units will fit over a four-barrel carburetor. I tried using a stock (2V) air cleaner on my 1985 model when I converted to a 4V carburetor and I seem to remember it wouldn't fit.


Right, and you also have to consider what specific air cleaner is on what specific engine. For example, Ford used the air cleaner designed for the 460 truck engine and adapted it to work on the 5.0 H.O. (302) engine found on the early 1980s Mustangs and the 5.8 H.O. (351) truck engines. If the 460 air cleaner flows enough for a 460 cubic inch engine, I find it hard to believe it would be restrictive on 351 cubic inch engine, or a 302 cubic inch engine - and with a second snorkel added.

I have read in several places that there is a 1% loss of horsepower for every 10 degree increase in temperature. So if the underhood temperature is 100 degrees higher than outside ambient air that could be inhaled in a cold air system, you would be down 10% in power.

Plus, a closed twin-snorkel air cleaner with the proper air ducts connected for cold air induction looks way cool - much cooler than the aftermarket chrome air cleaners everyone and their Mother-in-Law uses.


Exact-a-mundo!

 

When i purchased Blue Ox, she had an open air cleaner with a stand alone breather cap in the valve cover. During the winter months she was a very hard start presumably due to carb icing. During the summer she had a rough idle presumably due to not enough cooler outside air being fed in to the carb. I searched around and found a OEM air cleaner (1980 302 2v) with it's components and immediately swapped it out with a new filter element and internal breather element along with a new PCV valve. I also flushed the breather cap out four or five times with carb cleaner and replaced it's hose going to the housing with new neoprene. I did fabricate a new intake duct from the core (radiator) support to the snorkel from aluminum clothes dryer ducting. Being as how all emissions were stripped by the PO, her carb bowl vent is open.
By the end of summer here, she was starting with no issues with proper idle and just this morning being 5 degrees F, she fired up on the 4th crank and purrs. From my experience, open air cleaners may have their place but not on Blue Ox.....she doesn't like 'em.
What comes to mind is the Thunderbolt where the in-board high beam headlamps were removed and fresh air ducting installed to force feed cooler, fresh air.

 

Carb icing doesn't cause hard starting. The carb will not ice up until there is airflow through it from the engine running. So the icing happens after the engine has run for a little bit.

 

Guess I should have stated, hard start and poor idle in both hot and cold conditions.
Regardless, my point was.... in MY situation, the OEM air cleaner greatly improved both conditions.

 

I added a vacuum toggle switch to the vacuum line that runs to the temp switch in the air cleaner lid that controls the flap to the heat stove. That way I can warm the engine up with the heat stove and if it is warm out or I don't want the flap closing I can flip the switch and have it wide open. I do not have a stock engine and it likes the cold air from the grille. I had an open element and went back to the stock one with a K&N filter. It is not a race car and runs well with the stock air cleaner even if it does restrict flow, but I'm not totally convinced it does. I have heard various things in drag racing circles regarding air cleaners, specifically bases and lids. Apparently the curved or drop bases help smooth air flow into the carb better than flat bases. And I have heard of an engine that would not run properly with a K&N filter lid, apparently it messed up the air flow and a flat lid fixed it. I get the feeling air cleaners are sort of like hedders, it depends on a few factors whether there is much of a gain and is probably dependent on cam choice and engine size.

 

Hmm, listening to all this technical talk is interesting, but just think, more colder air is better! I am about to also take two 460 air cleaners and make a dual snorkel. Using an efi air inlet for the driver side grille opening. Sort of like the 1968-1969 oldsmobile 442 w30, there were inlets underneath the bumper, then in 1970 they were relocated to the hood.