[mchell]

Some may find this useful:

Playing around at the track recently, I’ve discovered a HUGE difference in Performance using different air cleaner bases.

Using the same 3” air filter, I have found my engine will ONLY perform adequately with the stock base dual snorkel and a filter top that just covers the filter, NOT the entire base like a stock lid.

Tried a whole pile of combos and nothing bested this combo.

The worst base( Alluminum with a sharper roll into the carb) reduced et by .3 and 4mph!!

Drop bases produced the same poor results.

Seems my qjet is VERY Sensitive to the base and will not tolerate anything but a stock shape??

Question:
Have any of you found a base and lid that will work better than stock ?

...wondering what I’m leaving on the table by not being able to use a 4” filter with a stock base?

This is all based on a qjet carbed engine.

On a good note I was able to get my first 6.981 1/8 mile et and a best 60’ of 1.52 on a different pass...not terrible for this old pig

Thanks for any insight

[steve25]

This chart may help explain your experience in picture form, and also folks should make note that once a given mass of air reaches a certain velocity it will not follow along anything greater then a 15 degree radius without sheering away from where you want it to go!

Just like water air wants to take the path of least resistance.

Also not that with Q-jets that the speed of the air entering the primary's is far faster then those big secondary's, so a air cleaner base with a bigger gentler radius around those small primary's helps a bunch!!

Don't hesitate to aid that radius shape with some epoxy.

Weather more air cleaner area will help you out all depends on how much HP the motor is making and how much air that perticular brand filter your running flows

[Formulajones]

Originally Posted by mchell

Some may find this useful:

Playing around at the track recently, I’ve discovered a HUGE difference in Performance using different air cleaner bases.

Using the same 3” air filter, I have found my engine will ONLY perform adequately with the stock base dual snorkel and a filter top that just covers the filter, NOT the entire base like a stock lid.

Tried a whole pile of combos and nothing bested this combo.

The worst base( Alluminum with a sharper roll into the carb) reduced et by .3 and 4mph!!

Drop bases produced the same poor results.

Seems my qjet is VERY Sensitive to the base and will not tolerate anything but a stock shape??

Question:
Have any of you found a base and lid that will work better than stock ?

...wondering what I’m leaving on the table by not being able to use a 4” filter with a stock base?

This is all based on a qjet carbed engine.

On a good note I was able to get my first 6.981 1/8 mile et and a best 60’ of 1.52 on a different pass...not terrible for this old pig

Thanks for any insight

Exactly what I like playing with at the track and enjoy reading posts like this.
I did this years ago with a couple different cars. I'm surprised you found gains with that filter top lid. I never could get those to work good for me.

Makes me wonder what kind of clearance you have from the top of the carb to the bottom of the lid when you're running stock lids? I've found that to affect performance just as much as the base used. With some cars it's impossible to get the lid far enough away from the carb to make any difference. So dropping the base for more filter is the only solution, but as you found, that has mixed results, sometimes not so good. I think the proximity of the lid to the carb is a big player. In fact tests have shown that a flat base works best with a 3 or 4 inch filter, which gives copious amounts of room above the carb, and lack of drop base gives a straighter shot of air to the carb, but that setup never fits under a stock hood.

Which dual snorkel are you using? I may experiment with the filter lid again next time at the track now that I have changed the setup around a bit. Basically most every car here is now using a stock air cleaner base setup with taller filters, stock lids. Mainly for fitment and functionality more than anything else. Waiting for the track to open again for more testing.

[Skip Fix]

When I pulled off the L-88 base and the 4" filter ion the 500" IA Camaro I picked up 0.3 seconds!

[Formulajones]

Originally Posted by Skip Fix

When I pulled off the L-88 base and the 4" filter ion the 500" IA Camaro I picked up 0.3 seconds!

You were using the L88 base with a full diameter filter and lid?

Those things were originally designed for a small screen and lid the diameter of the throat of the carb, with a filter in the hood. Just like in the picture of the one I built for dad's GTO.

Used this way they are very effective as the outside air coming in has a straight shot to the throat of the carb when the hood is closed. I think what helps this design is what I eluded to in my first post. The small lid holding the base to the carb is about 2 or 3" above the carb itself. Plenty of room. I forget how far that drop base is now, but it's alot. I would have to check but seems even a 4 inch filter wouldn't put the lid very far above the carb??

[mchell]

Another thing to add...

I did try NO filter and I also tried a stock base and lid with NO filter.

Both of these resulted in very poor et and loss of MPH

[Formulajones]

Originally Posted by mchell

Another thing to add...

I did try NO filter and I also tried a stock base and lid with NO filter.

Both of these resulted in very poor et and loss of MPH

LOL yep!!

I tried no filter in the stock base with the stock lid. It absolutely KILLED ET and MPH. When I tried that scenario, mine was in a ram air situation (70 RA Formula) with fresh air pushed in. Led me to believe the filter does act in slowing down the air flow and possibly straightening it to some degree to be more beneficial.

[mchell]

Action shot ....trying to unload..........getting closer............bwaaaaaaaaaaaaaa

[mchell]

Two of the base variants that produced very poor results....had to beat one into submission to clear the qjet linkage

[mchell]

This is the variant that provided the best performance....

Unfortunately, with a RPM intake it is the only setup I’m able to run without modding the hood.

[Formulajones]

Okay, so a stock style Pontiac dual snorkel base and a standard 14" diameter lid (not a filter lid)



I've seen setups similar to this at the track that worked well. I had a theory that keeping the stock base like you have sort of insulates the carb from ingesting a ton of heat, especially any heat soak coming up from the bottom.

Rather than a simple open element that isn't shielded.

[mchell]

Originally Posted by Formulajones

Okay, so a stock style Pontiac dual snorkel base and a standard 14" diameter lid (not a filter lid)



I've seen setups similar to this at the track that worked well. I had a theory that keeping the stock base like you have sort of insulates the carb from ingesting a ton of heat, especially any heat soak coming up from the bottom.

Rather than a simple open element that isn't shielded.

Yep.....works best on my rig with a qjet

[indymanjoe]

Originally Posted by mchell

This is the variant that provided the best performance....

Unfortunately, with a RPM intake it is the only setup I’m able to run without modding the hood.

What base is this off of? My dual snorkel looks longer in the snorkel? Did you cut it back some?

[mchell]

Originally Posted by indymanjoe

What base is this off of? My dual snorkel looks longer in the snorkel? Did you cut it back some?

Yes, the dual snorkel I’m running had been cut down in the late 70’s by the original owner of the car.

Although I have an original one that’s uncut, I’ve grown fond of this one and have been running it for 20 years or so..... I’m no purist by any stretch

[78w72]

Originally Posted by mchell

This is the variant that provided the best performance....

Unfortunately, with a RPM intake it is the only setup I’m able to run without modding the hood.

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.

[Steve C.]

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.


.

[78w72]

Originally Posted by Steve C.

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.


.

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.

[Formulajones]

Originally Posted by Steve C.

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.


.

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.

[scott70]

Originally Posted by mchell

This is the variant that provided the best performance....

Unfortunately, with a RPM intake it is the only setup I’m able to run without modding the hood.

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

[Steve C.]

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.

.