Thread: Drop base air cleaner

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Back to basics. Sorry if I have missed a discussion in a previous thread!
What is the advantage of the drop base? Sure a big-by-huge cleaner looks boss but is it worth it?
The way I see it, obviously is wrong so hang in there for a sec.

There is a larger area for air. Need air to breathe. So,
By lowering the base, it " seems to me " the lid is still going to be close to the carb throat. So, in my wrong view, what is the advantage? Does it help moreso than I am thinking?

Lets say the hood clearance is not a factor. Would it still breathe as needed with a 10 x 2 standard base compared with a 10 x 3 or 10 x 4 with a drop base?
So the base is dropped - the lid is not moved.
How is a drop base an advantage if the restriction is on the top side of the carb?
Again, sorry if I am beating a dead horse. Thanks for your patience :-)

Good Question! I agree with you that if the lid to air horn doesn't change, there wouldn't be any greater space to allow air through. But if the original filter housing lid was lower, then replaced with a drop base and the new one had a greater area between the carb and the lid, then obviously there should be a gain. And having a larger filter (in theory) should provide more surface area and slower airspeeds per cu.in. and give greater run times.

My 2 cents anyways!

I think what you're saying is that if the lid to the air cleaner is so close to the top of the carb that it's creating the choke point for air flow, then dropping the bottom of the air cleaner housing, and installing a filter with more surface area is not going to improve air flow, or performance and I agree with that analysis. If the top of the air cleaner assembly is indeed causing choked flow you could remove the air filter element and the flow would remain unchanged at WOT, and the only way to improve flow is to lift the lid to give less restriction to the air flow over the top of the carb, into the venturi's. Sorry if I've mis-understood your basis.

Very interesting views!!
I agree
larger areas = more available air
And I am thinking as rspears points out also.
A close tight lid " seems to me " to nullify droped base.

Originally Posted by t-top havoc

.....A close tight lid " seems to me " to nullify dropped base.

If you look at the principal of choked flow it doesn't matter what you do to the upstream/downstream conditions until you address the restriction that's causing the flow to choke at a specific point.

My understanding of this type of air cleaner was strictly a hood clearance thing, never read anything about a performance advantage of the design.

Thanks rspears & pepi.
Thaks to all for your input.
I just curiously wondered how // what advantage there was.
Great answers and great point about addressing restriction(s).

I had a flat base aircleaner on my 350 Chevy in the Bucket when I first purchased it on top of the Quad-jet carbie and as it was rusty I purchased a new drop based cleaner with a 4" filter and accomplished two things, one was more air into the carb and more important to me, was it helped hide the ugly carb somewhat that I didn't want to change as it worked absolutely brilliant. Interesting fact was when I went and viewed the Bucket before purchase it had a scoop with the 3 butterflies that didn't even open on top of the carb and it was the first thing that turned my stomach. I told the seller that if he replaced the aircleaner I would purchase so the deal was done.

I don't think that a 10 inch drop base will work on a Holley and would suggest that a 14 inch plus the K&N extreme top----don't get a combo that is so low with an element that it sets on the choke extension---probably should use a 4 inch element

I think I read a "study" done on just this question some many years ago. The findings were somewhat interesting: they found that the air moving over the curve of the base tended to increase velocity to some degree, and that the small restriction of a low cover increased that effect. At some point, though, things went the other way; either from too much restriction, such as too narrow of a filter that brought the lid too far down and seriously restricted air flow, or a taller filter element that raised the lid high enough that the Bernoulli effect was diminished or eliminated altogether, and turbulence took it's place.

Now there is some fodder for a serious discussion; go to it gents.

How's that for digging into the dusty, web choked crannies of my addled brain?

Unless you're going racing and tuning to the last 1/2 of a horsepower on a dyno, you'll never notice the difference between a dropped base or a flat base. Jerry mentioned the main issue, a 14" diameter is needed to clear a Holley carb and a 4" height on the element will provide plenty of airflow for a street engine.