trafficlightguy

looking to keep stock hood was wondering what would be the lowest air cleaner
It looks like a 1.5 would fit, iam in the process of mocking something up to get a more prociese measurement


thanks in advance
chris

blackbmagic

Get a drop base air cleaner housing. If that doesn't work you will have to go with a shorter filter or get rid of any spacers on your intake that you might have.

SuperHawk996xx

iTrader: (1)

I had this same problem on my 86' T/A. I have a four inch edlebrock high rise intake so I just used the drop down air cleaner with a 2" filter. fits fine.

Lockwood

I am having the same problem with my 1990 firebird formula, got a 14inx3in filter and the hood won't close and I'm having trouble finding a air filter that's around 14 in but small enough in height that it wont hit the hood. Any ideas on where to get one?

Night rider327

iTrader: (13)

Drop base air cleaner housing and a 14x3 filter should fit fine, if not try drop base with a 2.5" tall filter

skinny z

What kind of clearance do you get with your set up? What I found with the typical dropped base, which is generally around 5/8" (that's the actual amount the filter element sits below the carb throat gasket) is that the air filter lid gets very close to the choke horn with a 3" filter. Maybe less than a 1/4". This all marginally fit under my old IROC hood and I had to trim the inside hood frame at that. (RPM Air Gap intake). I went to a K&N X-Treme filter lid to keep the airflow maxed out. (Since then I've gone to a cowl hood and I have enough room for a 4" filter element.)

Night rider327

iTrader: (13)

Hey Skinny, just a heads up but those X-treme lids has been proven many times over on track and dyno to kill off power. I too was very shocked to learn this, but after another racer told me of his ETs with and with out I started digging into it and ALL the real tested info i found showed a drop in power with the X-treme lids.

skinny z

While I can't argue about it, it makes no sense. Unless of course there's some underlying issue like a poor air/fuel mixture (marginally lean) that's exacerbated by the increased air flow the lid provides....I suppose also that the increased airflow isn't as streamlined as it could as it passes over the air bleeds and boosters creating a buffeting effect similar to what happens when guys run their engines at speed with NO air filters. A 100 mph breeze passing over the carb really messes things up from a metering perspective.
Things that make you go hmmm...

firechicken_3

iTrader: (4)

I have a Vortec RPM Airgap, with various holley 4150/4160 series carbs edelbrock drop base and 3 inch filter under my 84 firebirds stock hood. insulation is gone but nothing has been trimmed

skinny z

What's the drop of your base? Do you know how much space there is between the lid and the choke horn? I'm pretty sure there's an ideal combination of parts that works but mine wasn't it.

Night rider327

iTrader: (13)

Yeah from what I read and looked into the lid causes alot of turbulence over air bleeds and boosters and messes with the vac signal, air gets "trapped" between lid and top of carb kinda. Really odd results

Ron U.S.M.C.

Yes that's interesting.
I always figured the rate of air passing into the actual intake was controlled by the sucking of air through it. Never figured a 5.0 or 350 would have trouble doing it in an basically enclosed space with any air regardless of a little turbulence .

Oh' sorry you are talking about carbs .and turbulence affecting the operation.

skinny z

The signal is very sensitive and needs a stable air flow to function properly.
The IABs and HSABs respond to the slightest change in air pressure so an atmosphere that's turbulent will have an overalll effect on the air/fuel mixture.
Even the flow on the backside of the boosters, that is the area immediately below the butterflies, will affect the overall carb cfm if it's configured one way or another. I.e., open plenum vs carb spacer (and type) vs two plane.
The right EFI is easy in comparison.

kenrussell3

I know I'm coming in on this a few years later, but the problem with "open carburetors" is the "venturi effect". The velocity of the air passing across an open tube creates a vacuum in the tube. The diameter of the tube (carburetor/intake) and the velocity of the air moving perpendicular to the opening (vehicle speed) determine the amount of vacuum. So, as you increase your speed with vertical inlet "tubes" (open carburetors) it tends to create a vacuum that opposes the engine intake vacuum (a negative "turbo" effect). That is why "ram air" is so effective. Since the air velocity is forced downward into the intake, the perpendicular "venturi effect" is eliminated. An air cleaner reduces the velocity and changes direction of the air entering the carburetor, eliminating the "venturi effect".

kenrussell3

By the way, an Edelbrock Pro Flow (part number 1221), fits perfectly over the Quadrajet and under the stock hood of a 1986 Trans Am. It has a 3/8" drop and comes with a 14" x 3" air filter.

skinny z

This is one reason to always run a filter. Ram air or otherwise.

IROCZman15

iTrader: (25)

even at the dragstrip? most drag cars I se are running no filters ? I do get what was discussed about the venturi effect, but most drag cars I see are no-filter setups ??

skinny z

That's one of those old drag racer things that gets perpetuated because of misinformation. An air filter restricts the CFM capability and reduces power was/is the thinking which is hardly true. From what I've seen it may be a matter of convenience too as a filter fitment would be difficult or impossible in some cases. The issue with the buffeting wouldn't be as pronounced if the hood is in place as you would think the air stream would be less intense that way. But if you can fit a properly sized filter, why wouldn't you?
Check out Chad Speier's thread about modifying an IROC air box and flow bench testing. Very revealing I thought.
https://www.thirdgen.org/forums/fabr...ir-intake.html