If you're not familiar with it, this is a 2"-drop 14" air cleaner base that was used on the late '60s & early '70s Corvettes (and?) because of their limited hood clearance. I've seen some folks on other boards say it's still a good option for anyone who needs a dropped-base air cleaner, but have no first- (or even second-) hand experience with it. There are reproduction bases available, so it's not a problem to find one. Any feedback here?

They are a good drop and clear most obstacles on the engine.
I use to run one back when I ran a LT1.
Now I run a GM alternator on a Mopar for the amperage. Go figure.

For comparison, this is a generic pic of the style of drop-base that K&N and Moroso offer, and which I've been using for years. Depending on the brand & part #, they have from about 1" to 1-1/4" drop, so not nearly as much as that L88 base.

This design isn't as "form fitted" around the carb / choke / linkage / whatever as the GM part. It makes me wonder which works better in the real world when equipped with the appropriate filter height that provides the same amount of clearance between the top of the carb and the underside of the air cleaner lid.

I was interested in this but I need to get rid of the choke horn effecting the pri side the most 1st.

Looks good.

More than fitment, I'd be concerned w/flow path but maybe it has little affect OR, a lot which makes a WB readout w/different changes fun and info is gained both good and bad..........

I use an aftermarket version on my 1050cfm 4150 style Holley.
Small supercharger under it.
Runs the same with or without.

Here's a cross-section of the Braswell air cleaner that's a 14.25" base and 15.25" top IIRC) so that the filter tilts away from the walls of the base. It also requires a spacer to raise the base above the fuel-level adjustment screws. Not sure if this is one for their 4825 or 4760 carbs. Also, no data on their web site as to how much the air cleaner sits above the carb flange, though... looks pretty tall for a drop-base setup.

Notice the taper on the lid to channel air down it's throat..........

The crankcase vent tube on the passenger side rear of original gm bases interferes with a double pumper rear accelerator pump mechanism, I believe they addressed this on the repops(?). Also I don't think it will sit down on a generic chrome "dual line" fuel line, you may have to run the factory GM style "Y" block and 5/16 fuel lines (fuel block to bowls), although you may be able to bend a chrome one down enough to clear.

I think the big issue will be how it sits down over the accelerator lever rod that sticks out toward the driver side fender, you may be able to eliminate it on a std trans car, but an automatic.....???
Just a little FYI from a former bowtie fan.

jess

The reproduction I was looking at said "no breather tube on base". Here's the current fuel line setup, but no pictures handy showing the throttle linkage side. The car has a manual valve body auto, so there's no kickdown linkage to get in the way.

Among other things...

Brad
Who made or where did you get the bracket that holds the pressure regulator. Nice looking piece.

Jeg's; they offer them for a variety of brands of regulators.

I run an Allstar air cleaner.

http://allstarperformance.carshopinc.com/product_info.php/products_id/4315/26098

I dont like drop base air clearers.. they
change the direction of the air(restriction)
but if you have to use them then you have no
choice... just remember ALL air cleaners are
a restriction.. I did a few years testing air
cleaners for Chrysler

I was running a spectre 3 inch drop base for a long time on my car. I went to a Moroso flat bottom to install a fuel pressure regulator mounted on the bracket like you have. I didnt actually install the regulator yet, just made sure I had room and its been sitting on the shelf since haha.

Anyway, my old one put the lid pretty close to the bowl vents/choke tower. I did notice a difference in how much I had to slip the clutch. Also it was pretty hard to really smoke the slicks when I dumped the clutch before, itd spin them and go. A 3k dump just ROASTS them now. It doesnt feel like I picked up crazy horsepower but the car is more responsive.

Also, with the flat bottom I could only fit a 2 inch filter, but the lid is still about an inch higher than it used to be. Ordered an RO23 scoop so I can run a taller filter, but wont be in for a few weeks.

Yes I've used one. As said, you have to remove breather tube for use with a DP carb. GM dealers can order this part#.

Thanks for all the replies; I have a couple of new ideas on what direction I want to go with my air cleaner setup now.

I did back to back testing at the track this summer. A K&N filtered drop base aircleaner vs. no aircleaner at all. Identical 11.41 times and mph with and without.

All you people say I didnt see any change.. did
you start changing jets to optimize without...
no... you took it off and didnt see a change..
because you were jetted with it on
If you have the room.. put a ideal entry on it
and see what happens.. you WILL be adding fuel

Try that w/a sealed scoop and get back w/us........

I had the same results as you. I am under the stock hood and it made no difference. I did the same test with EFI and it didn't matter. I have not tried it with the bigger motor yet though.

Made the pan for this summer already..

Well my wide-band didn't see the difference, so I am sticking with my opinion.

Then your seeing turbulence over the carb..
I will say it again ALL filters are a restriction
and its a proven fact... just because you didnt
see any change DOESNT change the FACT that a filter
isnt a restriction...

The real question is, is the restriction offset by the straightening/smoothing ot the airflow into the carb?

How much HP difference, on average, did your testing show?

Was it dynamic, real world testing or in a dyno cell?

This was on a filter flow bench... also just like guys
say that the filter top is better... I've done that type
of filter on the bench and at the track.. that top hurt
power... I have one right now but I put a plastic cover
over it.. reason why.. the 2 directions of air flow
hurt the total flow.... BUT you guys do what you want

On the same note, they also smooth out airflow apparently..........

Very well could be but that doesnt change the
FACT that ALL FILTERS ARE A RESTRICTION.. if
you have the space put on a ideal entry and
try it

I had to have a drop base air cleaner to clear my hood scoop after building my 434 last year. When I dynoed it the guys at the shop were asking me about my set up and I mentioned that I thought I was going to need a drop base air cleaner. They recommend the one in the link I posted and said it made more power than any other air cleaner that they had dynoed.

Ok... I quit... filters are GREAT.. they arent any
restriction

Mike pleas re read what I posted. They didn't say it made more power than NO air cleaner. It made more power than ANY AIR CLEANER they had tested.

I hear ya Mike it's just a b$%^h to street drive and not give something up unfortunately to keep debris outta the motor. K&N apparently did some dragster/pro stock scoop filters but never really heard the results........

They might. I just haven't seen enough restriction to warrant removing the filter. Especially when I race at a lot of tracks where we park on dirt/grass.

No need to get pissy. Just sharing my personal testing and results...

Looking back, my car was .10 quicker w/the hood/sealed pan on than off in the 1/8th...............and 1 mph...........fwiw........

That's NOT what he said. In some racing, dirt cars for instance, you MUST run an air cleaner. If the shop Justin was using does a lot of dirt car motors, they test those type things. At least that's what I took from the post

And this was his other post Monte... as I said
EARLY in this.. if you have to you have to..
still doesnt say its NOT a restriction.. which
I STAND BY

A couple of us have quantified our results with real world data to back it up...

Just because you use words like "FACT" and "RESTRICTION" doesn't make it so in every case.

And this was his other post Monte... as I said
EARLY in this.. if you have to you have to..
still doesnt say its NOT a restriction.. which
I STAND BY
[/quote]

A couple of us have quantified our results with real world data to back it up...

Just because you use words like "FACT" and "RESTRICTION" doesn't make it so in every case. [/quote]

So you say a filter isnt a restriction... now
I will ask... do you have a scoop and have you
ever put a ideal entry on it(you might call it
a stack)
EDIT
I put a high flow filter on my car at the track
with my scoop and a ideal entry.. it slowed down
.15(thats 150 thous)with a high flow.. with making
jet changes to find the best mph

An oil filter is a restriction too but it's still a good idea to run one
My home track was a dust bowl and I wouldn't even think about running without one
I just don't think there is enough "restriction" to hurt the performance of an average bracket car and so far there is no proof that it does

Gus

Thats fine.. I have said my last response on
this

What's your point?

I've re read all my posts and I never said an air cleaner wasn't a restriction or they made more power than no air cleaner. Brad asked if anyone had used a particular base for an air filter. While it's not the base he is asking about I posted a link to the one I use. It is relevant to his question and it may be cheaper than a repop piece for a Corvette. Plus it will work with a Holley carb.

Monty is correct, the shop that dynoed my engine builds and sells lots of engines for dirt track cars, so it's good business for them to know what works best.


Even hicks in Kentucky were taught reading comprehension is grade school.

The L88 filter base can be used with very tall 14" filters to minimize losses through the filter.

I use it on my Holley but I needed a spacer to get it above the carb in order to clear everything. I like the way its rounded cross-section helps the air on its entry into the carb.

Mr. P talks about an ideal entry and in my mind this base is pretty close to one. An ideal entry is one that creates minimal losses on entering the carb. Most of you haven't taken Fluid Dynamics and might be interested to know that there are losses that occur anytime the flow has a sudden contraction or expansion. The square corner entrance has higher losses than a rounded "ideal" entrance.

I'm leaning more towards a 16" drop-base designed for 5-1/8" neck carbs, whereas pretty much every other 16" filter setup I've seen has been offered only for Dominator-type carbs. I think it, too, has a 2" drop, and might require a short (.5" maybe?) spacer.

Haven't seen one first hand, just something I came across w/in the last day or so that caught my interest. I might be limited to a 16" x 3" element, possibly a 16" x 3.5", depending upon how much the lid sits up over the level of the filter itself.

Thanks for explaining that so some of them can
understand it... the new filter housing I'm
looking at has a nice entry and is a dual snorkel
so I can route in outside air from the front end
and I'll run the Wix high flow filter.. I'll still
have to run a drop base but as I said already.. gotta
do what ya gotta do

I like it.........

I determined I may need to stay with a 14" filter setup, based on what appears to be lack of clearance to use a 16" with my fresh-air plate. Maybe it's still possible to do it once things are back together enough that I can check clearances with the parts fitted up. However, at this point, I'm holding off on the 16" assembly I was interested in using.

My current plan is to run the Moroso-type 1" drop base w/ a WIX 14" x 3.5" AP-series (Asphalt/Pavement?) element and see whether the Moroso or K&N metal lid works better. There's definitely room to use the fresh-air plate w/ a 14" setup, and I'd really like to keep the filter in place while still having the carb sealed to the hood.

Back from the dead after 3 years...

Recent eBarf purchase was a used Braswell 4150 air cleaner setup. I took some pics of it to show overall height, etc., compared to a Moroso drop-base combination with a 3.5" Wix racing filter. The Braswell uses a 4" K&N element that is 14.25" at the base and 15.25" at the lid, along with a short "sure seal" o-ring spacer.

Views without the lids...

And...

Finally, swapped the Moroso lid for a K&N lid, which is roughly 1/4" taller in the center.

So, the surprise to me was the Braswell assembly is right about the same overall height as the Moroso with the 3.5" filter. Also, I didn't go with a 16" air cleaner like I showed above because 16" is too wide to fit under the opening of my hood where the scoop mounts.

I've seen that air cleaner before but it didn't have a Braswell label. There was someone who used to sell spun filters. (spun rather than stamped) I wonder if Braswell was buying them and putting their label on them. Be interesting to see if there is any difference on the engine.

Do you need someone with a running car to back to back test them for you?

There are a number of spun aluminum air cleaners being offered today, but I don't know how many are the same product from different vendors.

One of the common issues with most of those 14" drop-base designs is the bottom of the filter is effectively blocked off because the base rises at about 90* from the sealing surface for at least the first inch. Between the Braswell filter being tapered outward from the base and the base itself being laid back right from the start, I believe the Braswell is a better design.

Picture shows same two bases as above where you can see how they angle away from the filter.