Just want to add there are shorter air gap clones like the professional products and assault versions and possible jegs/ summit rebranded ones.
I have one and it is shorter than an edelbrock version. 4.65 I believe..

 

I’ll probably start hunting around for one of the aftermarket L88 style 2” drop base filters.
I have the ability to cut out small sections where it will interfere with the carb, form and weld the newly formed pieces to make it clear everything.
Then I could have it powder coated to look as good as new.
If anyone has one of these aftermarket L88 2” drop bases laying around that they want to get rid of, let me know.
Greg

 

It is only the air pipe that is an issue.
The rest of the base is the same.
If you do not mind "messing" around with that a little bit, these two versions are in stock at ZIP.

 

Forgot to mention: I have a cc 218-224 HR w/1.6RRs.
Very happy w/powerband.

 

Greg, look at Braswell. They had a very highly recommended drop base air cleaner set up that all the engine builders at Speed Talk raved about. It's pretty trick as the top is bigger than the base so the taper helps with flow. I think it was close to a 2 inch drop as well. If you google Braswell drop base air cleaner assembly, the second thing that comes up is the discussion on Speed Talk about it. I still might try it one of these days.

Bill

 

Just found this.
Typical air pipe modification to fit a double pumper.

Cutting it and welding in a flat angled piece would be so much neater....just sayin'

 

I hate saying this because it's an argument that many will simply call "opinion" but here it is anyway. If you are using a standard 14" round, 3" tall air cleaner element with your "drop base".......I'm gonna go out on that limb as suggest you're dyno guy is DEAD WRONG. You're probably not losing much of anything at all vs a flat base air cleaner with a 14" and 3" tall air filter. In the video the engine used makes 750HP. So the differences in performance will be bigger in the tests. Your results would be smaller than what is found in this testing.

Don't want to watch the whole video? Check out the 9:46 mark for the drop base results. Down 12.7 HP to the best over all number. Then at the 10:07 point the flat base comes in at a Down 10.1hp. Again it's worth mentioning that this is a 750HP engine they are working with so that limitations for virtually all the filters will be found. If your making less power the 2-3HP difference will be even less and very possibly no different at all if both can easily support the power you're actually making. I'd bet on a typical sub 500HP small block chevy or even a big block rocking just over that number you'd see no difference at all between the the two.

Save your money here..... spend it on something else.

That's my opinion and the video backs me up. Might be interesting to hear what the dyno guy knows or thinks he knows and how he backs it up with evidence of a pretty big 20HP claim.

 

That's interesting Lars - when swapping over to the Air Gap inlet on my BB '68 due to difficulties with the stock gas pedal linkage/cable/carb bracketing I was forced to use an aftermarket 'billet' carb bracket with the generic Holley DP the installed. That meant changing the stock drop base filter (L36 engine) to a lower 'drop' aftermarket base (this still has a 'contoured' shape like the stock base.... just not so low). The issue then (and even with a repro L88 style hood) was that a stock 3" filter element and filter top were too tall to fit under the hood. I simply changed the filter to a 2" K & N Airstream filter 'top'. The L88 hood is open at the rear. Filter top to hood clearance is perhaps 1/4"/3/8" at the front and 3/4"/1" at the rear. The K & N filter certainly appears to be really unrestrictive........I presumed the losses from changing to a 2" vs stock 3" element would have more than compensated for when using the K & N 'top.....

but your comments re. the height of the stock 'domed' air filter top make me wonder about the efficiency of my installation?

 

I have been using a complete factory L88 Hood and the Wedding Cake Assembly that was made to use with the L88 Hood for decades. The hood has an air box attached to the bottom of it and this has a hole directly over the carburetor. My 427 has a Edelbrock Performer RPM Air Gap intake with a Holley 850 on top of it. Using the foam seals for the wedding cake, the hood actually seals quite effectively. This is something that allows the pressurized air to come in from the base of the windshield and then it turns down and goes straight into the carburetor. There is not much as far as air filtration so I use the foam air filter and oil it like a lawn mower air filter. Then I put a K&N Filter "Cover" over the larger screen and that does a fairly good job. This keeps the moths, butterflies and firefly's out of the carburetor for the most part... While cruising the air going into the throttle body is very close to ambient temperature and this is critical to using a high compression engine year round.

The L88 hood does offer more room for tall intakes, but that is NOT what makes it such a great part to use. The reason they made that hood like it is was so they could get Cooler Air into the engine making it tolerate the high compression reducing or eliminating detonation. That makes this hood really special and very valuable for anybody running the 12.5-1 compression of an L88 engine. This hood helps the high compression L88 engine work on the streets and making it more drive-able and useful. I drive my 12.25-1 compression Corvette on the roads regularly and use 93 octane fuel with little to no problems. When my engine gets really hot I activate the water/methanol injection system and this pulls the temperatures down quickly (as the water/steam evaporates) and gives the engine 116 octane fuel.

All of this is possible because the of the cooler intake air getting down the throat of the carburetor and making power without detonating. This is one of the best cold air intakes used on a factory stock Corvette. Between the few air flow restrictions and the hungry engine, the sound of that engine opening up with all of the air being pulled from the hole on the back of the hood is awesome.

As far as the drop bases go I use the one with the breather "tube" sticking out. A "screen cap" goes over the hole and the breather pushes any waste air into the intake air flow so it will be burned. This breather tube is not a bad thing and looks great when used with the silver screen over the drop base.

Today I have a Holley Stealth Sniper EFI system on top of the Edelbrock Performer Air Gap Intake. It is tall but the hood with the air-box will close over the top even with the tall Stealth Sniper Throttle body. Next will be a multi-port intake and a dry throttle body using a Holley Terminator. This will make more room and make the engine even easier to live with.

The Drop Base that was designed for the Corvettes has the notch in it for aligning the Holley carburetor base. It did not work with my Edelbrock carburetors as it would not fit over the carburetor. The factory drop base fits over a Holley Dbl pumper or a Holley Vacuum Secondary and looks like they made it to just that. It worked well for my Holley Double Pumper as it will for a Vacuum secondary carburetor. Since I don't use vacuum secondaries I am not positive it will fit but knowing GM it most likely will.

The tubes that they modified on the Holley double pumper were which tubes? The Vent tubes? None of my Holley carburetors have a Choke horn on them. There was no problem running the tall intake with a Holley 850 on it. I lucked out because the gentleman who sold me the L88 hood had the other parts left over from his L88 race car that was wrecked. He mailed me the entire wedding cake with the original drop base that came on a 1968 L88 Corvette. I never expected the box of goodies but they were sure useful making the hood fully effective which helps my 427 make (more) power.

 

---

 

K&N "filter" is just a gravel strainer - I only run it when I drag race

 

I've seen several mention that the K&N Lids do more harm than good, the late Joe Sherman verified this on his dyno and reiterated the same!

Edit, I believe it was also sussed-out during an Engine Masters dyno session also, with the same results!

 

I found and measured an original 2" drop base air cleaner today.


Believed to be an original GM. The drop from carb flange to base was 2.0"


Stock 3" filter measures 3-1/4" high.


From the carb base to the top of the lid measures 2.0" Maybe 2-1/8".

Lars says you need 3.0" at this location, above the carb, not 2.0", for max power.

Engine Masters says this style costs 12 HP. Over none. And if you do not have a 752 HP engine, it is likely less.

But it might be as big as you can get and still fit under the hood!

But on some cars maybe a 3.5" high air filter would fit?
And that would raise the lid some more!

A 4" high filter on Engine Masters cost almost no HP. Maybe 1.5 HP. So raising the lid really works.

 

I remember watching my engine being Dyno tested and seeing the difference of the 3 inch vs 4 inch filter. I believe Alan Rothman tested his as well and found the exact same thing on his, or maybe a little bigger difference. What I witnessed on mine confirmed exactly what Lars said. I think the other thing that is underrated about the L88 system is isolating the intake system from the under hood air. I worked hard to make sure my system totally isolated the intake air from this.

Bill

 

I ran one of these for a while too and never noticed any issues because I dont race the car. In the engine masters showdown though they show that the air coming in from the top interferes with the air coing in from the sides and causes a lot of turbulence which in the end makes this filter perform worse than the cheapest no name chrome/paper 14 inch filters out there I now you dont want to hear this as I didnt either and used it for similiar reasons as you chose it but the testing was pretty conclusive. I have the misfortune of not checking my aces killshot throttle body for clearence till aftr I purchased and found I cant run any type of drop base which puts me in a quandry with my drop base cold air intake.

 

Augie,
You might not need the tall dual plane with EFI. I would not worry much about low RPM torque impact. This is a real small plenum single plane. Big inch SBC has plenty of low speed torque. You probably wont notice any real difference there. EFI will fix that. Healthy top end improvement. I really like your cold air intake and would do whatever you need to keep it. A Weiand IMCA single plane would be worth considering. You can get the hood closed and make great power. Check out the paragraph 2d in the EFI Sticky in the Tech section.


Popular IMCA racing single plane. Easy to find and very low profile.


This Weiand Team G Street Ram intake below would also be good but they are very hard to find. It's a baby single plane that works great for a hot street car.

Weiand Team G 7525 EGR style intake. Long out of production. 2000 - 6000 RPM range. Very low height to fit under the hood of any C3. If I did not have it, I would just buy the IMCA intake above.

 

I 'hear' and understand what you are saying - the thought that originally went through my mind using the K & N Filter top was that it 'visually' would appear to flow more air than the 2" reduced height filter (that I had swapped-out from the stock 3"). Part of that logic was that even though the K & N filter top was quite close to the underside of the L88 style hood....with the K & N's relatively open filtering material it would improved 'breathing'. I did draw-up some plans to fabricate an air box to encapsulate the carb and draw cool air from the rear (bit didn't get around to it). I might look at an alternative to the 'billet' throttle bracket and re-use the stock OEM drop-base and re-gain the lost 1" height.

 

Hello there roscobbc,

If you are going to go that much work why don't you buy the the air-box made for the original L88 hoods? My hood came with the air-box attached and it seals very tightly around the throttle body keeping the combustion air even cooler.

I have seen people that sell aftermarket L88 hoods selling the lower air-box part that you can attach yourself. It is already shaped to fit and it really works with the L88 hood which might make it the easiest option available. It is not that heavy or even big so it could be shipped to you in England.

When you have the wedding cake assembly on top of the drop base the carburetor has a small cover that goes over a round screened piece that keeps big stuff out of the carburetor. On my engine when the hood is closed that lid is almost touching the hood above it. This allows the air to enter the carburetor and turn downward in to the combustion process with great ease and a high flow rate. This system is very simple if you have the room to use it. I put a spare SB in my C3 while I spent almost a year re-building the 427. The L88 hood worked even with a SB as long as you made the parts fit by using spacers.

Air filtration using the complete L88 hood can be difficult. I have the large screen above in the hood like they used from the factory. I wish they made a nice K&N filter that would fit up there but it would be very hard to install and maintain. If you could filter the air as it comes into the hood opening, that would be great but restrictive. I use the K&N "outerwear", it is like a tightly woven fabric that goes around the outside of an air filter and keeps the stuff out of the carburetor. I have one in the hood around the (oiled) foam element and another for around the little round screen inside.

Currently I have a Holley Stealth Sniper EFI system on my C3 and it works okay with the L88 hood but it is tight. I am using the Edelbrock Performer RPM Air Gap intake on my 427 as well and it is just too tall for everyday usage as it touches the hood. I am planning on going to a single plane Holley Intake with a dry throttle body using a Holley Terminator EFI Controller. This will open the space up and make the intake system a bit shorter.
The Stealth Sniper does work well with the 427. I love how it looks like a carburetor and it could fool many IF it didn't say EFI on the sides. The Stealth Sniper sits on the engine like a carburetor where the Sniper has the throttle body turned 90*.

Cool air and cooler fuel will help any BB make lots more horsepower. I wish you the very best in your effort to make the Corvette even cooler than it was when new!

Best regards,
Chris

 

Thanks Chris for your very informed reply. Yes, you may well be right about sourcing 'repro' :88 style hood 'innards' - advantage I.m guessing being that you'll know it will all work - whereas making your own set-up could be a very much 'suck it and see' scenario.
Interestingly it has made me think about the way my specific car behaves in heavy summer city traffic. The typical 'fluffy' response off-idle in city traffic when running hot previously I put down to engine heat soak and early stage percolation. But now I'm thinking whether elevated underhood induction air temperatures could instead be responsible. The temp gauge typically runs up to 185/190 in summer traffic, and very rarely in to the low 200's. I could try running sans hood - this would obviously allow all built-up underhood heat to escape, carb to draw-in ambient air temps and perhaps better replicate how the car would behave with a functional cold air intake.
Ross

 

The vent I installed in my hood acts as both cold air intake, allows heat to escape and creates a vacuum behind the radiator to pull in more ambient air.
At least that’s what it should do!