thebruce

I have looked through all the posts that mention hood clearance and the RPM Air Gap manifolds, and I don't know what to make of it. I like what I have read about that manifold enough to know I want one, but not if I have to buy and paint a new hood. SO....

With a stock '74 hood is there a drop base air cleaner that will allow it to fit? I have a Q-Jet right now, but I'm planning on getting a Holley or Demon soon, so I also need to know if there is enough clearance to fit a Q-jet carb to square bore intake adapter in there before I get the new carb.

Thanks. :flag

rainman69

The Q-Jet won't work (well) on the RPM Air-Gap. It's designed for squarebore carburetors only. :smash:

63Banshee

Back in the day we air gapped our own intakes. They were lower rise then the current air-gap intakes, but it still functioned properly up to 5700 or 5800. If you don’t plan on running higher rpm you could consider an intake equivalent to a Performer dual plane and air-gap it yourself. Sounds cheaper and less work anyway… just thinking out loud I guess.

gerry72

Dave,
The "Air Gap" isn't from milling the plenum divider down. It is because the runners are open to air circulation...like on a tunnel ram or as occurs naturally on the intake on your RB engine in that Dodge. The Air Gap is the same design as the RPM manifold, just with the runners exposed to cooler air.

Now as to the original question...
The best way to make this judgement is to put a glop of Playdough on a couple of places arough the top of your air cleaner, then close the hood. Open the hood and measure the thickness of the now compressed glop of Playdough for the one with the least thickness. This will give you the clearance of your current setup. Go to Edelbrock's website and get measurements of the manifold you're interested in. Using their drawings, make the same measurements they used on your current manifold. Do the math. You'll need at least a half-inch of clearance in the end to accomodate engine movement.

DeenHylton

I would say it will NOT fit with a stock 74 hood. Before I installed my blower I had a Holley Street Dominator manifold that would be physicaly equivalent to the original "RPM" manifold with no-air gap. I ran a Moroso drop base (around a 1.5 in. drop) air filter assembly and Holley carb but had to use an after market air filter of around 2.5 inches to shut the hood and allow 1/4 inch for clearance. My car is a 77 but I believe the hood clearance is pretty much the same. Just as the post above explains, I too used modeling clay to double check my clearances...Deen
P.S. I did have a 3/8 inch heat sink style gasket between the manifold and carb, even without it a 3 inch filter height would be risky.

Clink69

Isn't your hood a L-82 hood? I am not sure but I thought that was higher than the L-48 hood. If that is the case I bet you can make it work from all the postings I have read. The RPM Air Gap is a really great intake and I want it on my new 383 in my 69 \BUT it just won't fit. The 68-72 hoods have less clearance than later L-48s. What is the difference between L-48 and L-82 hood for 74? Can someone answer that? :flag

RatRacer

You will need a L-88 type hood to run the Air-Gap manifold.

ylose

you could go with a Performer/AIR GAP

or RPM/Air Gap + drop base air cleaner or Pro-Flow air cleaner ? (not sure here)

or RPM/air gap + FULL AIR CLEANER + my extra *new* hood. :D

:jester

GROSSPOLLUTER60

I'm using an rpm air gap with a drop base K&N extreme filter assembly. This all fits under the hood of my 78L48 hood.

john355

i have the air gap rpm manifold with a drop air cleaner base with stock hood L48 fits fine

Red73

This fits under my stock 73 Hood.

thebruce

Looks like I'll get the manifold, then do the playdough method to see what else fits. Thanks for all the input.

Anyone know if there is a drop base manifold that isn't going to cost me as much as the Moroso or the K&N? I vaguely remember someone recommending a manifold off an old camaro or something. :flag

Captain Morgan

Red73,
What carb do you have on top of that Air Gap?

Red73

sharklover, 750 Speed Demon. Rod
:cheers: :cheers: :cheers: :cheers:



[Modified by Red73, 9:34 PM 12/5/2001]

thebruce

John-

What brand/ model drop-base are you using?

rob75383

thebruce,
I have a '75 with the L48 hood.
I am running the RPM Air-Gap with a Holley double pumper, and a 14" K&N drop base air cleaner.
The drawback to using the RPM Air-Gap with a Holley double pumper is that you have to forget about using the vacuum port off the #8 cylinder. I have a plug in there, and have teed off my PCV to the brake booster to the rear of the holley, and have the headlight/ vent vac line teed to the trans module to the port on front of the carb throttle plate.
I don't know the EXACT clearance, but I couldn't fit a .275" thick shim between the secondary accel pump on the carb, and the vacuum port on #8.

Check out my photos, look behind the carb pad, and you'll see that the plug is just about flush with the carb mounting pad... forget about fitting anything under a holley without a spacer. And once you use a spacer, there goes your hood clearance.




Here's a picture of when I mocked it all up to check for clearance.

I haven't tried the clay trick, so I don't know how much actual clearance I have.


[Modified by '75 383 ElkGrove, 3:53 AM 12/6/2001]

thebruce

Wow. Great pics. I've already decided to go ahead and get a square bore carb (probably a Holley) when I get the intake, so I won't have to worry about the carb adapter problem. Thanks for the heads up on the vacuum routing-- I'll probably try a setup like yours. Thanks a bunch. :cheers:

thebruce

GrossPolluter60 (I love that name, by the way)- What carb are you using? I'm wondering what carbs a drop base aircleaner will fit over.
Thanks.

MotorHead

This is what I have in my '80 to give you another alternative, it's a 9 inch K&N setup with Extreme top.

I did not like drop base assmeblies as it covers up half the motor.

I did the calculations and there is enough air flow for over 5000 RPM. For serious racing though I would use another setup.

TeenagerWith74Vette

I have the RPM Air Gap under my stock '74 L-82 hood. I have a 750 Holley and a low profile filter. It might touch my my hood under full throttle, but I don't think so. You should be fine with that intake. Jay