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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.
Usually the lid is the restriction It come down to clearance between the the choke housing and the lid. Also if you look at the air flow path in some (not all) the air cleaner lid inlet runs smack in to a ridge or baffle. Some times even the inlet that runs from the air cleaner to the rad support are a restriction. This was especially true on the 7.3 IDI diesels. Ever check to see how much clearance there is between the inlet of the stock set up and the back of the front of the hood. It is about an 1".
Every install is different some are pretty good other (Like the 7.3IDI ) are horrific.
Ideally you want smooth transitions with lots of clearance at bends.
And no they did not go though a lot or of trouble to get the coolest inlet temps. Hence the need for things like hot idle compensators. Some carbs even come with these built in. So not exactly a huge effort in stabilizing the upper limit. The real solution for stabilizing under hood temps is stuff like cowl induction or venting, Hood scoops or even behind the grill inlets. And getting heat out the engine bay is as important as getting cool inlet air in.
On most vehicles there is no control to limit upper temps short of hot idle compensators. Efforts were made to try to keep it from getting to hot but there was no actual control to limit it.
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.
From the other thread.
An open air cleaner does not make the secondary's open later but the exactly the opposite, secondary opening is determined by venturi vacuum and the venturi vacuum is dependent on air flow, not manifold vacuum, a restrictive air cleaner will make them open later as the engine won't be able to breath properly thus able to move less air thus lowering ventri flow thus making the secondary's open later.
Not sure where you guys get some of these ideas from...... but jeeze.
With an open air cleaner they will open sooner as the engine can actually breath properly and move more CFM of air at any given RPM this increasing venturi vacuum. There is a reason Ford and others used open air cleaners on performance applications in the 60's.
The Autolite 4100 uses a tube that protudes in to the primary venutri's utilizing the vacuum with in the venturi to open the secodary's. This is one of the things that makes the 4100 so adjustable as not only can you change diaphram springs but you can fine tune it with placement of the tube in the venturi.
The open style air cleaners have been dyno proven to add up to ten and even more over HP over the stock units. Beside being better flowing they tend to better smooth out the air flow in to the carb with less turbulence and can actually allow for more accurate fuel metering.
And really you should be doing a pre winter tune up on carb'd vehicles that see cold temps for optimal operation. From 80F to-15F the air density change is equivalent to a 3000 ft change in altitude. Which is enough actually to warrant a jet change. Every 2000ft change in elevation is equivalent to one jet size either lean or rich depending on if you are going up or down..
Back in the day winter and spring tune ups were standard practices and you have to pull the air cleaner to do this any way so swapping from one to another is a zero time and effort job.
In general, heavy cars require stiffer secondary diaphragm springs than light cars. Air cleaner
configuration and restriction plays an important part in spring selection, so be sure to use your
air cleaner when evaluating your vehicle’s performance after each change. An installation with
an open element air cleaner will require a weaker spring than one with a restrictive snorkel-type air
cleaner.
Usually the lid is the restriction It come down to clearance between the the choke housing and the lid. Also if you look at the air flow path in some (not all) the air cleaner lid inlet runs smack in to a ridge or baffle.
The lid is the restriction? I don't understand what you are trying to say here.
And what is an air cleaner lid inlet? Are you referring to the snorkel?
Originally Posted by matthewq4b
Every install is different some are pretty good other (Like the 7.3IDI ) are horrific.
What about the 1983 - 1985 Mustang 5.0 twin snorkel air cleaners? These had air ducts that fed cooler, outside air directly into the air cleaner, which makes it a true "cold air" intake. A few other performance cars had these also. The 1970 Oldsmobile 442 (Outside Air Induction) for example.
Originally Posted by matthewq4b
And no they did not go though a lot or of trouble to get the coolest inlet temps. Hence the need for things like hot idle compensators. Some carbs even come with these built in.
What is the difference between the hot idle compensator that are found on some Autolite 4100 (and Motorcraft carburetors), and the later 3-port ported vacuum switch that connected to the distributor vacuum advance and switched timing from ported to manifold vacuum when temperatures got too high?
Originally Posted by matthewq4b
The Autolite 4100 uses a tube that protudes in to the primary venutri's utilizing the vacuum with in the venturi to open the secodary's. This is one of the things that makes the 4100 so adjustable as not only can you change diaphram springs but you can fine tune it with placement of the tube in the venturi.
Interesting. I always wondered what that little tube was for.
Originally Posted by matthewq4b
Back in the day winter and spring tune ups were standard practices and you have to pull the air cleaner to do this any way so swapping from one to another is a zero time and effort job.
I am too young to remember when most people had vehicles with carburetors as daily drivers, but did owners typically perform a jet change on their carburetors every Spring and Fall? (I find that rather hard to believe.) Was that procedure actually addressed in the Owner's Manual that came with the vehicles back in the day?
I find it hard to believe that an open element air cleaner will do better on the dyno than a single snorkel air cleaner with a duct to the grille like factory on the 460s. Without a duct, yes. Are these dyno tests with the hood open/off? With a fan blowing wind? So many variables. To me, air cleaners go as follows from worst to best:
Single snorkel no duct
Dual snorkel no ducts
Open element
Single snorkel with duct
Dual snorkel with duct
Blower/bug catcher sticking through the hood!
Most of the tests show an open element compared to a single snorkel with no air duct. On our trucks I would say this wasnt really fair because some were equipped with air ducts and some were not. It is so easy to add one on so why not? There is even a slot on the drivers side of the radiator support for another air duct. I think that one is for the efi trucks though. I picked up the hose end part off a truck with no motor. Just a quick cut up and it will have the full duct work and soon I will mod the air cleaner to have the other snorkel. Just need to get a different oil cap.
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.
Yes and no. Again depends on the set up Some are ram air and are usually labeled as such, but most are not.
GM's restrictive snorkle was actually used to reduce engine/inlet noise.
If it was same diameter all the way to the carb's throat then there could be an argument for ram air effect but as soon as you open up to the air cleaner housing any velocity gained is lost. Even GM in performance applications used either open air cleaners, Cowl Induction etc.
Uncorking a restricve air cleaner with no other other changes may show low end decreases in power this will be to due leaning out the fuel air mix you now have more air but not necessarily more fuel.
This is sort of like that fallacy that engines need some exhaust back pressure to make max torque down low.
Once again this is where the swap between and open air cleaner and factory for winter works great as you may richen up the mix for the winter which is exactly what you want.
The factory Ford system used in the 70's and 80's have NO ram effect at all.
The quickest way to tell is any system has any ram potential is the placement of the PCV in let. If it is in the air cleaner housing or inlet system the system will not have any ram effect at all. This is a quick way to tell if a system is a ram system or not if the PCV feed is in the inlet with no pressure limiter it is not a ram air system.
There is a very simple reason for this. If the system is to have ram effect and build pressure in the inlet system and the PCV is feed is in that system you will also be pressurizing the crank case and potentially blowing out engine gaskets (intake front and back, valve covers) and seals (front and rear main) Ask me how I know this.....
I built a very effective a ram air set up on a 351W utilizing a factory Ford single snorkle air cleaner and 4100 Autolite many years ago. What I failed to modify initially was the PCV feed, needless to say a blast down the hyway resulted in enough pressure being built up in the crankcase to completely blow out the rear intake gasket it was completely gone other some small chunks stuck to the engine block it had been contact cemented in place on the block.
The gasket blow out was violent enough and produced a huge enough cloud of smoke and burning oil smell that I thought the engine had let go.
After getting home and realizing my dumb assery for having failed ram air 101 basics. a new intake set and removing the PCV feed from the air cleaner and changing from a screw in oil cap to a breather type oil cap then blocking off the old PCV inlet hole in the cleaner housing ,things were good to go with a very substantial gain in power above 60 mph. This also resulted in better hyway fuel economy also. And things got even better when a ram air dual snorkel was fitted
Moving the inlet from under hood to the rad support was done to try to mitigate hot idle issues, it did not completely stop it or prevent it. The factory system is not designed to limit the upper temp as it is the lower temp. Help reduce the upper temp potential yes, but not limit it.
Whether there is ram air or not, a snorkel air cleaner with ducts is way better than an open element regardless of ram air.
Not always. See 7.3L IDI for example. And once again open elements have shown up to an over 10HP gains over stock units. You guys seem to think all of these systems are the same they are not. Some are quite good others are complete trash and a caveman with rocks and tin cans could cobble together something better.
Not always. See 7.3L IDI for example. And once again open elements have shown up to an over 10HP gains over stock units. You guys seem to think all of these systems are the same they are not. Some are quite good others are complete trash and a caveman with rocks and tin cans could cobble together something better.
That is a diesel, we are talking about gas motors. Can we see the tests?
So, if the lid is part of the problem then creating a tall HO air cleaner by melding the bottom half of one and the top half of another could be advantageous. Make it just the right height to accept one of the taller filters and use the same lid. But, since the lid will now be above the flow, or at least partially out of the flow, then the ridge won't have the same effect. Right?
And, I understand that factory air cleaners don't control the high temp, but they certainly reduce it, which has to be good. And, you said "The real solution for stabilizing under hood temps is stuff like cowl induction or venting, Hood scoops or even behind the grill inlets.". That's exactly what the factory air cleaner has - behind the grill vents.
Here's my plan, using factory parts. Both sides are plumbed to the radiator support, so there should be plenty of cooler air than if an open element unit was used.
So, if the lid is part of the problem then creating a tall HO air cleaner by melding the bottom half of one and the top half of another could be advantageous. Make it just the right height to accept one of the taller filters and use the same lid. But, since the lid will now be above the flow, or at least partially out of the flow, then the ridge won't have the same effect. Right?
And, I understand that factory air cleaners don't control the high temp, but they certainly reduce it, which has to be good. And, you said "The real solution for stabilizing under hood temps is stuff like cowl induction or venting, Hood scoops or even behind the grill inlets.". That's exactly what the factory air cleaner has - behind the grill vents.
Here's my plan, using factory parts. Both sides are plumbed to the radiator support, so there should be plenty of cooler air than if an open element unit was used.
Thats exactly what I plan to do also. What inlet piece is that on the driver side?
Sure go on line and do the searches it's pretty easy to do, I'm sure you can handle it.
I'm sure there is no doubt that it can be "handled"....You mentioned open air cleaners used by Ford Performance during the 60's. How would you explain the forced induction used by FoMoCo on the Thunderbolt through the headlamp openings on the factory sanctioned lightweight drag cars ? Having been a member of the now defunked Performance Ford Club of America and My Brother owning a factory Galaxie SOHC 427 Lightweight car....which does not, nor ever employed an open air cleaner, I'm finding it a tad hard to follow.
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