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Air filter versus cold air intake

3K views 13 replies 10 participants last post by  MouseFink 
#1 ·
My engine runs a little bit warm. I do live in Arizona and the 100 plus degree temperatures do not help. I am running a 383 and I am trying to cool the engine down a little. I am installing a cowl hood, not for performance but for looks. I was wondering if a larger/taller air filter would help with temperature/performance or if a cold air intake system would help more.
 
#5 ·
^^^THIS!

Nearly every aftermarket "cold air" system I've seen deletes factory piping that really does ingest colder air from outside the engine compartment and instead sucks hot underhood air. :rolleyes:

Apparently consumers are really gullible. Of course, the open element air cleaner that comes with these aftermarket systems is louder than stock, so the "butt dyno" always says power increased with the noise. The only actual performance increase is from the weight reduction in your wallet.

To the OP's specific question, a larger air filter will allow more air into the engine. Unless you re-jet to match, you will be running ever-so-slightly LEANER, which tends to increase engine temps. This is not the solution to your problem. Also, the base of the windshield is a HIGH pressure area. A cowl induction hood will NOT vent hot underhood air, it will cause air from the base of the windshield to flow into the underhood area. There's a reason why cowl induction hoods exist.
 
#6 ·
In the early1970s, I had a 1966 Pontiac GTO with factory tri-power and a Ram Air intake pan and hood. One of 200 made that year. Merely removing the three small paper AC220 air cleaner elements was worth 0.2 second ET improvement. I determined that no improvement was a result of the cooler outside air. I ran the GTO with and without the Ram Air sealed air cleaner pan and saw no change. However, there was a slight improvement in air flow at high RPM with the paper air filter elements removed and the Ram Air pan in place.

The 1966-67 GTO and 1967-69 Firebird 400 hood scoops were too close to the hood surface for good cold air intake. That was because of too much surface air resistance. The air flow went over the scoops.

A elevated air intake would have an I provement in dense cold air induction..
 
#9 ·
You have to be careful with a cowl facing hood scoop as at speed a high pressure area forms ahead of the windshield which will reduce if not reverse any hot air escaping from under the hood.


Air filter flow ratings were done by David Vizard and I think are in his book "How to Build and Modify Chevrolet Small-Block V-8 Cylinder Heads". The K&N is the most free flowing of any. It is important to remember that the filter when clean can flow to a maximum number of CFM. Once the demand from the engine exceeds this number then and only then does the filter begin to impede flow to the carb or FI system. So if the filter is capable of flowing 350 CFM and the engine demand is 200 CFM the filter is no obstruction to flow.


I have long been a proponent of keeping OEM closed air cleaners for a couple reasons:


1) Those with thermostatic inlet air valve where they select from preheated air drawn past the exhaust or from cold air often sourced behind the grill allow the termination of the intake manifold's exhaust crossover without a lot of penalties. This allows a colder air source that can be had with the crossover active; yet when the engine is cold it offers a heated air source which helps prevent icing that is common to carburetors and throttle body injection where there isn't an exhaust heated intake manifold. It also provides better fuel atomization when the engine is cold which allows for less choke usage which reduces the fuel wash on the rings and cylinder walls that causes a lot of the wear these parts see. Understand that most OEM air intakes are designed with silencing the air flow so they tend to be too small for high RPM use, but they provide the model for an effective system of controlling induction air temperature with what the external environment permits. They should be modified to supply the engine's needs rather than substituted with some ineffective aftermarket gadget.


2) The snorkel type air cleaner is easily modified for a cold air source. This needs to be nothing more than a flex hose from the snorkel to a location behind the grill or front bumper. All that is needed is to obtain an air source that is outside the engine compartment. There are many commercial units for sale or you can fab your own from Home Depot parts for a lot less money and still have all the effectiveness. I shy away from below bumper designs as this is an area where there is a lot of road dirt to contend with that quickly decreases filter efficiency. Understanding that living in the desert southwest has its limitations of the definition of "cold".


There are several methods of getting the under hood temps down one of the most effective is using stainless steel or ceramic coated headers if your budget can stand the cost of these. They do a lot to keep the heat inside the pipes and out of the engine room. The next, but very effective, thing is to wrap the headers with heat tape which is also quite budget friendly.


Bogie
 
#11 ·
My Suburu has one that looks very ,uch like that last pic except it terminates with a cone style filter in front of the RF tire. The inner wheel liner got a cut in it and water would splash on the filter so rain driving wasn't very good untill I made a box for it.

K@N are pretty old school with the washable and reusable R2C filter that flow better and filter better.
 
#14 · (Edited)
I made a performance comparison with the carburation on my 1969 Firebird 400 w/ 4-speed. The original equipment was a 700/800 CFM Rochester Q-jet with secondary opening limit lever. That device was only installed for vehicles measured by 1967-1970 HP/weight insurance rating. If not for the secondary opening limit lever, a 1967-1970 Firebird 400 would be in the same insurance category as a 1967-1970 Corvette. That insurance rate cost about $1500 per year..


The lever in place limited a 800 CFM Q-jet to 700 cfm. Of course, I removed the device with tin snips to achieve 800 CFM at WOT with the Q-jet. After installing a Crane Z-500 solid flat tappet cam, 428 full size Pontiac exhaust manifolds, chambered dual exhaust, and a 4.33 rear gear, I thought I could use carburation with more CFM, ........."Mores Law".

I installed a friends 1966 Pontiac Tri-Power set up and lost 0.5 second ET. I reinstalled the modified 800 CFM Q-jet and regained the ET I lost with the tri-power.

The 1966 Pontiac tri-power with Rochester 2G, 2GC, 2G carburetors flows about 675 CFM at WOT but it sure looks cool when you pop the hood.
 
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