Air flow
 

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

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

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.

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??

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.

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

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

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.

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

:thumbup:

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

Nice testing..fun part of the hobby! With that 1/8th mile time that is a sub 11.0 time

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

Great thread, loving seeing threads like this, real world testing!

Based on my testing years ago q-jets seem to be pretty sensitive to how the air enters. We made a top that was very nice, by cutting the choke tower off and really smoothing out the entry (like a holley) and it hated it.

Makes me want to find that old pic of Jim hands carb and air cleaner base. He made some forms that fit to the carb and blended it to the base. I’ve seen it and thought “how much difference could that make”

Now I want to duplicate it....it could make much more of a difference than first thought....

Are they here ?

https://pontiacstreetperformance.com...455jh2006.html

.

Thanks !

Looks more complex than I thought.....give me something to play with

The base he’s using looks exactly like mine.

Holy cow 3/10s and almost a full tenth on your 60' is huge! That air cleaner setup looks great and I wonder how it would perform on a Holley. Great pics and I'm jealous of you guys down south that can still go to the track now.