Yes, thank you have looked at the NASCAR setups. I had gone as far as researched particular duct fittings etc. Some IMSA type brake ducts would work well, and there is a wide variety. Some have small openings, but there are some that are used for directing radiator and cooler air flow, those would work great.

EDIT: I was going to use a carb hat, and a cooler duct on the cowl, with a hose between. Carb hats provide a lot of flexibility as to where you mount the filter. Once you remove the limitation of size/space from the top of the carb, the sky's the limit.

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I know from track testing on cool nights my cowl air cleaner takes full advantage of the cooler air.

The one cringe-factor is though, cutting into the cowl/firewall.

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I tested different bases (also some elements) on a chassis dyno, about 10 years ago. I've posted results before.

The biggest drop base (the rounded one, in your photo) was down 10+ rwhp across the entire test I performed, compared to other bases.

I've seen losses over 30rwhp with certain filter/bases combinations, on the dyno.

Using a higher rise intake may give someobdy a few HP, but they can lose all of that and more with a restrictive filter/housing.

On the Year One Bandit Trans Am project with a 535 combo Jim Butler used a Victor intake with the carb flange milled down 0.650" to help it fit under the hood. With the cut down intake he used a WFO drop base unit for the TA Shaker scoop. Tested on the engine dyno at peak power rpm it gave up about 15 hp by milling the intake.

On my current 505 street engine prior to the fuel injection I did the same thing with a Victor intake & HP950 carb. On the dyno I lost about 8-10 hp at peak power rpm after milling the intake flange 0.650". Not a race deal so for me I did not miss the 8-10 hp on the street.

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No comments on the air cleaners/filters, but on the same topic:

In a different lifetime, when I still had time to build carbs; built several for the circle track racers that, by rule, had to run a single Rochester 2 barrel. Found by actual racing that leaving the choke butterfly in place made the cars faster than removing it! Used to remove the choke shafts and mill them almost paper-thin, then reinstall and pop-rivet the choke butterfly in place, and zip-tied the arm to always be in the fully open position. The butterfly acted as a straightening vane to help the air coming into the carburetor.

Be interested see dyno results, but the track time proved the modification.

Jon.

If you use the factory stuff, the cool factor of a real cowl plenum will quickly diminish any cutting concerns ;)

In the car crowd I'm around, anything with a factory appearing cowl plenum setup is Ooo Aaaa at any local car event, if people actually know what they are looking at. Especially if it's a car that fits the era that these things were used.

All that stuff is reproduced now, or like I mentioned earlier, RamAirBoxes sells a fiberglass aftermarket version that doesn't technically look like an original setup but it uses the same idea. I've had in the back of my mind to run one on the nomad if I ever get that thing on the streets.

If you go the carb hat idea, I did that in the past on my little H-bodies, but I didn't tap into the cowl, I went to the front grill area. That's the nice thing about the carb hats, you can point them anywhere and run a 4" hose anywhere you want. I even went as far as to rob all the turbo inlet stuff to the carb from a 79 turbo regal eons ago for a factory appearing setup.

I will say the cowl plenum stuff works extremely well though if you're looking for a clean way to do it. My chevelle I mentioned earlier is the same idea, grabbing air from the high pressure area at the base of the windshield, and the IAT temps I've monitored are always nearly spot on what the outside ambient temps are, as long as I'm moving.

In fact our 69 Z has the same setup. I have the door removed from the hood so it's functional all the time. I don't have a way to monitor the IAT's on this one but I can say after driving it in the early morning when it's 20-30 degrees outside, I can pop the hood and put my hand on the top air cleaner lid and it's ice cold, in fact everything inside the hood seal is ice cold, but the base of the air cleaner outside the hood seal that is subject to engine heat is very warm to the touch.

That's nice info. Years ago I added the factory divider piece to a quadrajet and it was good for almost .5 mph...The car I had at the time was consistent but not super fast..it would run 99mph without it and 100 mph with it...dis 6 passes one night back to back to test..I think I'm going to try a funnel type divider next year to see if it does anything.

Lord .... you guys are going to make me put my choke butterfly back in and try it...who knows?

Being in South Florida I’ve had no use of a choke of any sort. Like most, I thought less junk in the way must be better, so out it came.

Keeping that choke flap in place works out for the better on Q-jets and 2bbl Carbs due to as Carb king posted which ties directly into the greater air speed of small Carb bores like they have.

I've found very similar results and have tested all sorts of air cleaner assemblies, lids, filters, etc. Over the years I've mentioned this numerous time but often it goes on deaf ears. Makes me wonder how many folks have added a taller intake, or spacer(s), then a drop-base set-up and think they are making more power than what they removed?

In any case I can find no combination of parts that runs as quick in ET or MPH as the factory Shaker base, stock filter, lid and open Shaker assembly pulling all the air in from outside.

Some of the parts I tested actually induced a HUGE hesitation/stumble/bog going quickly to full throttle, so much so that I couldn't get a good drag strip run using them.

The K & N X-Treme lid was the WORST part tested. With it in place it was impossible to make a full pass at the track, the engine just "puked" all over itself on the starting line. No lid at all it was fine, or the stock lid and no issues.

IF I put any of those "flat" lids in place it did basically the same thing as the K & N lid, so some set-ups can be very sensitive to this sort of thing.

In any case with all runs the quickest in ET and MPH for back to back testing has been the factory parts and stock height air filter. Even replacing it with a K & N filter gained NOTHING, so much for all that marketing genius.......FWIW......Cliff

Thats exactly how I run mine,,factory dual snork base with a simple factory style filter and a lid that just covers the filter.

Related to testing a K&N X-Stream Air Flow Top filter. Testing has supported that the entrance on a Holley 'HP' series carb with it's smooth contour does in fact act like their Stub Stack and will help it work with the X-Stream lid. Whereas a Q-jet carburetor and apparently a Holley carburetor without a smooth contour (with a choke tower) doesn't work well with a X-Stream lid.

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These test results may be interesting to some here!

What height and diameter filter do you run? Does your shaker style hood allow for a taller filter? Also, have you run shorter filters(2”)? How did these affect your performance?

On the X-treme tops, I've had mixed results - on the same motor!

A friend had a Cobra replica, with a 408 inch stroked Windsor. The first time I had it on the chassis dyno, he had a rather small K&N filter with the X-streme top on it. That filter choked off over 35rwhp, with the motor putting about 435 to the wheels with no filter.

That block died (stock Windsors tend to do that when stroked), and he had a new 408 built with a Dart block. That motor was putting 475hp to the wheels, and he installed a much larger (diameter & height) K&N, but again used an X-treme top with it. To my surprise, taking the filter off had no effect this time. He was running an HP-type Holley on the second test, and I don't remember if that was the same carb he had on the first.

Good info...the chart is of interest

I would suspect that at over 500hp a taller filter (4” +) would be ideal...14” diameter a minimum

The dyno’ s are tough as they can’t duplicate what’s going on under the hood at different speeds and intake air temperature’s... they will offer indicators tho....

A fwiw tid bit, according to K&N a larger diameter, short filter will flow more air than a small diameter, tall filter.


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Mike, thanks for starting this thread; really good info to put to use. Curtis and I have done a lot of testing in this area over the years and there have been many 'surprises' along the way. The main one, which has already been pointed out, concerns filter vs. no filter. We never found a combo where running no filter was better. In fact it always resulted in slower et. We are currently using the ram air box on both cars. The Bird has the 14x4 box and my T/A has the 14x3 box. I don't have enough clearance for the 4" with the RPM intake. And we have to use a drop base also. But the real advantage, I think, to using the ram air box is it allows us to run the 4" duct into an area of cooler air. On the Bird we actually were able to cut two 4" holes in the core support and attach the duct right to the grill inserts. Some have said that there is a slight 'ram air' effect when speeds reach 100 mph or so. Not sure if that is true or not but it sounds good anyway. Years ago when I was still running the standard open element air cleaner I decided to remove it and try one of the 5" velocity stacks which fit right nicely in the hood opening where the shaker assembly would normally be, and to my surprise the car ran consistently quicker. I assumed that the air charge would be cooler, but I thought there would be a lot of turbulence over the stack and that would be a problem. Apparently not. All the more reason to not assume anything but go ahead and experiment.

Excellent info!.....hope y’all are doing well!