stc315

I have a 72 454 Coupe with the L88 hood. I plan to install a Performer RPM Air Gap intake on it with a 750dp Ultra Holley carb. The hood shield opening is only 12" and most drop base air cleaners are 14". Can anyone recommend an air filter assembly to help clear the hood?

ajrothm

Are you talking about the L88 plenum that's glued to the bottom of the L88 hood like a factory L88 setup?

If so, then just buy the L88 air cleaner with the foam ring/Chicken wire mini screen...Then put the factory size filter up in the plenum. Basically just copy the factory L88 setup...

Or better yet, take the air plenum off the hood, run a regular LT1/L78 style drop base (2" drop) air cleaner with a 14x3" element. It flows better then the L88 chicken wire mini air screen/lid that sits right on top of the carb, and its not shrouded by the perimeter of the air chamber.

My car lost 6 rwhp with the L88 chicken wire/mini lid compared to running a LT1/L88 base without a lid/filter. Now with a 14x4" air filter, I lose no power at all...(but I have a high rise L88 hood now)

stc315

Yes, I was referring to the air plenum. I was looking at 11" air cleaners with 2" filter. Not sure how much restriction that will cause vs. drop base. I also have to consider clearance for HEI. I think the 14" will clear HEI, but can't remember (been a while since I've had a BBC).

ajrothm

You need this:
https://www.paragoncorvette.com/p-34...mbly-l-88.aspx

Stick with what you know works.

I wouldn't try a traditional style air cleaner lid/filter when using the air plenum. It would choke it down.

With the RPM air gap, you will likely have to trim the foam down some as that intake is much taller then the stock L88 intake. The air cleaner base will be very close to touching the air plenum.

I know the RPM air gap, L88 drop base air cleaner and 3" element will clear an L88 hood without the air plenum and have about 1/4" of clearance... Having the air plenum will be the wild card as to if it all fits. You'll have plenty of clearance for the HEI with a 14" air cleaner.

stc315

Thanks, it seems most of the aftermarket drop base air cleaner assemblies only drop about 1.25-1.5". I think the GM drop base assembly (L78 etc.) is about 2" drop. Trying not to spend so much on air cleaner, but looks like I may not have much of a choice lol.

stc315

I'm also seriously considering trimming the plenum opening up to 14". Figure I can make a jig to mark it and cut it with a jigsaw.

ajrothm

The only problem I see with cutting out the plenum for a 14" filter is the filter will be shrouded by the sides of the plenum. The plenum isn't that wide as it is... You may only have a couple inches on the sides of a 14" filter shoved up in the plenum.

It may affect you, it may not.

I researched the air plenum thing a lot when I was putting my car together.. After playing with air filters, bases, lids, hood up vs. hood down on the chasis dyno, I determined that the carb does not like to have anything sitting on top of the venturis, even with the choke tower removed. Also the car runs faster with the air cleaner base on and no filter/lid then it does with no air cleaner at all.

The shape of the L88/LT1 style base is pretty good for making HP.

I would probably stick with the L88 air cleaner setup IF the base clears the air plenum ok (due to the taller rpm intake). Otherwise I think I'd take the air plenum off all together and run a regular 14x3 air cleaner with the 2" drop base.

I know a lot people have tested running the carb sealed to the hood and rear open scoops and not seen much, if any gain on the track.. I think it's more of a gimmick then anything.

Now a forward facing scoop and a sealed air pan to the carb is definitely worth some power.

All depends on how hungry you are for power.

I have tons of pics of different air cleaner setups and L88 hoods if you're interested.

roscobbc

If choosing to use 'drop down' 14" diameter base with RPM Airgap AND aftermarket billet throttle bracket you'll find stock drop down base is too low to fit over bracket. I went with 'higher' Edelbrock drop base AND 2" filter element. Made up for potential loss of air flow by using Air Stream type air filter 'top'.

stc315

Thanks, I'd love to see the pics. I see plenum removal in my future lol.

stc315

I was planning to re-use factory bracket for right now. Thanks for the tip, I'll keep that in mind if I switch brackets.

stc315

Got it all installed. RPM Air Gap with Endurashine finish and Quick Fuel Q750 carb. All fit (barely) under L88 hood. I had to use a bolt instead of a stud for the air cleaner. I used the cheapo summit drop base air cleaner. I also replaced M/T valve covers with polished aluminum short valve covers (look similar to factory chrome valve covers). But now after getting it all together, finding oil leaks that I didn't notice when I got it home (just bought car a few weeks ago). So next project will be pull the engine and replace bottom half gaskets and seals. Will also replace power steering hoses since I have a power steering leak too. While I have the engine out, I will pressure wash engine compartment and rattle can black the frame rails etc. I will also take the time and paint the engine back to stock orange (faded and greasy). I may also replace the oil pan since I have it out. Anyone got any recommendations for higher capacity pan? I've been looking at one of Summit's pan kits.

stc315

Pic of progress

stc315

another pic

ajrothm

Moroso 20403 pan works/fits well.

MelWff

you may also want to consider getting rid of the fan spacer, installing a fan clutch and non-flex factory style fan.

The13Bats

I understand racers etc wanting every drop of hp and the L-88 air cleaner all fitted to the L-88 hood is really neat-o cool to me, my L-88 hood has that air box, but I didn't know if I wanted to be locked into that one air cleaner set up.

In fact I collect old school custom air cleaners, some are just wild silly looking restrictive engine art but for me fun to play with and swap around.
I hate to cut the air box out of my hood but will likely just pull a mold of it and run an L-88 hood with no air box.

I would never want to run with no air filter and curious if these type tops would have a place in some applications,




I was looking around the forum at hood scoops and ram air type ideas and curious how are builders keeping these things from directing rain right down the carb or FI?

MelWff

i have seen comments on a number of sites that the breathing tops actually disrupt airflow into the air horn and reduce power.

TheSkunkWorks

I'm somewhat curious as to whether the L88 flame arrestor (aka, the little chicken wire screen thingy) v 14" x 3" filter test could have fully accounted for the important differences between the two induction setups. The complete L88 CAI setup (base, flame arrestor, air box...) is designed to benefit from a higher pressure area which develops at the cowl ahead of the windshield at speeds as low as ~30 mph. And, that air is "cold" (the "C" in CAI), meaning inducted air is at ambient temperature rather than having been heated within the engine compartment. I respectfully submit that these induction chamber pressure and temperature differentials should also be factored into the equation, difficult as it may be to actually perform an objective scientific test. (Sorry, I don't currently have access to a full-scale wind tunnel with a rolling floor chassis dyno.) Anyway, JMHO.

commander_47

That is awesome.

Looks great and I know the performance is amazing!!!

Nice job!

The13Bats

The K&N flow top is just a re booted new school version of this old school classic and we all know That "motion" the worlds fastest bestest wildest etc vettes etc ad nauseam ran the Fly eye...
Even though I was told basically all my life that the two worse restrictive air flow distrupting air cleaners ever made were the fly eye


^^^ mine..lol.



and it's cousin.


We all know what how forums and forum member "opinions" go,
I would have to see some real world unbiased test results to believe any "air cleaner" is better than the next on 99.9% of the cars here and the way they are used...

However, air intake "systems" like the L-88 with cold air box have some real tech behind them, I would believe some shaker scoops did real well too.