Just to clarify:

The .3 and 4mph difference was from changing my “normal” base/lid combination to other combinations mentioned above.

The worst of these “other” combinations resulted in a .3 et gain and a 4mph loss....other combinations were slightly better than the worse but still waaaaaay slower than the “normal”.

The 1.52 60’ and 6.891 1/8 mile were recorded the same day using my “normal” base/lid combination.

Hope this helps

Yep.....might’ve cracked it but I screwed up my 2-3 shift and ran an 11.04....still a best but disappointing

Could always try a blow thru hat with a tube and cone filter.


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that base & lid looks nice. very similar to what i run on a 72 firebird with a formula hood that has terrible clearance & doesnt allow for an RPM or other taller intake, i run a SD ported HO intake & Q-jet.

the base & lid i use is a W72 T/A style with the wide oval snorkel, it has the smaller lid like yours from the factory that leaves about 1-2" of the air filter exposed around the perimeter & has a tall dome for clearance to the top of the carb. after reading your results i will just keep this set up & not mess with aftermarket drop bases.

i did try a k&n filter lid the first time at the track with no hood on the car, ran 12.2... with no other changes besides the W72 air cleaner & installing a hood i was in to the mid to upper 11's the next time out. changing to M/T drag radials from worn out BFG drag radials i was doing low 11's. these were all different days so the improvements are hard to say what changes did what, but they were almost a half second each change.

good to know the factory drop base are close to the best set up for a q-jet. i like the epoxy mods jim hand did, kind of like a "stub stack" for the q-jet.

I was looking at possibly using the cowl area, build dividers to block off one of the square openings, and use a flat filter.

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Regarding the Holley carburetors and a similar situation Jim Hand did for the Q-Jet carb and the mention of the Stubstack. Testing has shown that the contoured venturi inlet on the Holley 'HP' series carburetors offers balanced airflow for increased horsepower over a carburetor design with a choke tower. The Stubstack with its smooth contour cleans up the flow and the engine responds to that.

https://www.knfilters.com/racing/stubstacks.htm


A fwiw, it's nothing new. One of the all time best custom carburetor builders Brad Urban did a similar thing many years ago. On his high performance Holley carburetors for maximum airflow the choke tower was machined off and he did a CNC radiused air entry.


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wish they made a stub stack for the q-jets. i still have a stub stack from back in the 90's when i ran a holley carb.

Yep I did that back in the 80's to a 3310, milled the choke horn and spent a ton of time with a flapper wheel smoothing the contours of the bore entry, and even used a little epoxy in small areas.

That was a whole bunch of work for not much gain at all, lol. I still have that main body. It went on the shelf when affordable main bodies that looked much prettier started hitting the market.

I never could find any gains with a stub stack. Not sure why, but after all that work modifying that 3310 with little benefit I wasn't the least bit interested in making a stub stack look-a-like for a Q-jet or even modifying a Q-jet air horn for that matter.

What is interesting though is that home made funnel Jim used on the bottom of the lid. Some of the OEM lids found on Chevrolets that have a much deeper recess for the wing nut kind of mimic this and I can see how that may be beneficial.
Some of the aftermarket aluminum dome lids you see used a lot on sprint modifieds also have this feature.

I however have no room for that mod on my Formula. With it's factory ram air setup, the bottom of the lid at the wing nut is only 1/4" from the choke horn, and I have no room at all to move the lid higher.

The biggest gain I've found with air cleaners at the track is finding a way to ingest outside air.

All the air cleaner setups I've tried never worked as well as the factory cold air setup on my ram air Formula.

I'm surprised Mchell that with your 71-72 GTO hood you haven't tried the same air cleaner my Formula has. They are reproduced and aren't overly expensive.

I found similar differences with my Chevelle and it's cowl induction setup. The difference in IAT temps is night and day.

It's very effective. Chevrolet did the cowl plenum in 67-68 on the Z before eventually moving it to the rear of the hood in 69.

There are ram air boxes made of fiberglass now, I believe the company is "ram air boxes" and they do have a cowl plenum setup that accepts a 14" filter element, bolts on like a factory air cleaner. Just have to make the hole in the firewall and fasten with the rubber sleeve and you're there.

I'm still looking FJ, but am not finding it. I know on 2nd gens there's a shaker kit that uses a flat filter, but forget which one was the better one. Blocker maybe?

I can't do the cowl setup on my 'bird, I welded a brace along the cowl lip and not going to remove it. I used a piece of angle iron and ran it pretty much from hinge to hinge. I was getting movement when using the structural braces so beefed it up.


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I haven't seen the flat filter. Blocker does sound familiar. From the sound of it, you are sticking with the shaker setup? Sorry I thought you were looking for the cowl plenum setup.

My body is using the short bushings, so it's tight. I fixed the shaker to the hood, lack of options at the time it was done.

Yeah, just checked, it's the Blocker Performance one that uses the flat filter:

http://www.blockersperformance.com/products.html

I may be limited to that type of setup with the intake I'm running. I think there was another one that also uses a flat filter, but would have to search it.

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That's slick, and fits with a Victor intake even!!

The other one is WFO Performance one that Butler carries:

https://butlerperformance.com/i-2445...tegory:1234772

I can't find the original WFO website, interesting...

Yeah, some work with the RPM, and some can accept the victor. One I recall specifically requires the shaker to be mounted to the hood, forget which one.

PTFB makes one too, but uses a round type filter.

http://www.pro-touringf-body.com/engine.html

All offerings on the Butler site:

https://butlerperformance.com/c-1234...a-shakers.html

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My 71 hood is capable of using the same ram air setup that was used on 71 gto’s and the formulas.

However there are trade offs and complications associated:

- the rpm intake sits A LOT higher, throwing the sealing geometry off and likely not allowing hood clearance for the air cleaner at all
- the pan and air cleaner assembly is weighty, possibly negating any benefits

You did give me an idea tho. Might try sealing the forward edge or back edge of the air cleaner base to the hood with foam to figure out if it likes air from the front of the engine or the back. Might reduce turbulence as well.

Can only try.

I am going to try a mock up of the the Jim hand carb mod to improve air flow into it.

FWIW, many years ago on my 67 GTO dirt car, I tried the cowl source of air with a 73 style air cleaner with the fuzzy hose connecting the air cleaner to the cowl area. It was the same idea that Jim Hand used on his wagon. It worked well enough that the buttmeter could discern a difference over just under hood warm air.

The problem was that not only did it pull in higher pressure air, it also pulled in a ton of debris such as dirt and small stones that ended up in the air cleaner housing. Looking back, I should have done some further investigation into this modification and solved the problem with a screen, or a layer of cloth to keep the larger stuff out.

Whatever the reason, I never tried it again, but probably should have as the cooler air, with some positive pressure, definitely made the engine run better.

Ah, I didn't realize you had a taller intake manifold. Yeah this setup doesn't give much wiggle room for clearance.

I've never been able to make the car run better with any form of an open element air cleaner in there though, so they are worth the investment if you had the room.

What you are thinking about now (sealing the front edge of the air cleaner) Is one reason why I believe your setup you have now works the best out of things you have tried so far. I've seen people do that before, and I think it's the factory base that somewhat shields the hot air that radiates off the engine and is somewhat of a shield for the hot air the fan blow back off the radiator. Where as an open element does none of that.

Now that I'm monitoring IAT's with a Sniper Stealth unit on one of the cars it's amazing how changes like this affect the temp of the incoming air. What is even more interesting is watching the computer change the fuel demand when you change the IAT's. So far with fresh outside air coming into the EFI, and early morning ambient temps in the 20's, my IAT's are 30 degrees when moving and I can watch the EFI add as much as 12% fuel. So it's easy to see why a cold air package is beneficial at the track and why my Formula slows down without it.

For inspiration check out some Nascar cowl setups and also the "Jim Hand" style of tubing off the cowl.

Exactly, where I got the idea for doing the cowl setup on my dirt car. The pressure is high at the base of the windshield because at 50 MPH there is quite a bit of airflow into the interior of a non A/C car..:2cents: