What is the advantage or disadvantage of these?

 

Isolate the intake charge from engine heat.... cold air is denser... denser = more oxygen = more fuel that can be burned = more power

 

It keeps the underside of the intake from being heated by the hot oil that splashes up on the bottom of the intake from the lifter valley, plus less conduction of heat from the heads up into the intake as well.

Plusses: slightly more power from a cooler intake charge.

Miuses: worse cold-weather drivability and increased engine (ring) wear from decreased fuel atomization under the carb. I.e. liquid fuel "puddling" in a cold intake.

The factory always used intakes with an exhaust crossover underneath the carb plenum area to heat it becuase the "minuses" outweighed the "plusses" in factory applications.

For a weekend fun car or street/strip vehicle an air gap intake is probably appropriate.

For a daily driver that you depend on to get you to work/school every day even in the dead or winter when it's 20* outside, you should probably follow the factory's lead and stick with an non-air gap intake WITH an exhaust crossover beneath the plenum.

 

The big thing that is quietly left out of the hype is that they don't have the exhaust crossover for EFE (early fuel evaporation) and hence don't have a port for EGR.
The Air-Gap intake feeds the engine a cooler air charge to make more peak horsepower during WOT.
There is a big difference in a Performer manifold and a Performer RPM manifold.
All Air-Gap manifolds are RPM manifolds. This is the difference most people see.
Now back to EFE. When the engine is cold (especially with a bigger than stock cam) you have to run more choke since the manifold isn't heated by the exhaust crossover. With more choke you have fuel puddling in the manifold at low speed.
Ask a few people that run the Air-Gap manifolds about the stutter and black puff of smoke when they gun the motor that has been idling for a while.
It depends on the application.
A car that rarely sees the street and is at the track: go Air-Gap.
A daily driver or occasional stripper would be better off with an RPM non-air-gap (yes, they do make one).
Just my
p.s. there'll be people also that swear they run a single-plane on the street everyday without problems .

 

I agree with everything else you said, except that all Air-Gap are not RPM manifolds.
There is a Performer Air Gap (p/n#2601) and a RPM Air Gap (p/n#7501).

As a matter of fact, if you go with anything other then a Performer series, you'll lose EGR capability.

 

Yeah my car is a street/sometime (whenever it would be ready) take to the track. What I dont understand is...supervisor, you say all air-gap manifolds are rpm, but if its not an air-gap...what does that make it?

 

That would be the standard Performer RPM:

http://www.edelbrock.com/automotive_...perf-rpm.shtml

The Performer RPM Air Gap would be this:

http://www.edelbrock.com/automotive_...-air-gap.shtml

And by the way, there are air gap versions of various other manifolds available besides the Performer RPM Air Gap, but that's one of the most popular.

 

I stand corrected on this. There is exactly one Edelbrock non-rpm, air-gap manifold for the SBC.
Edelbrock makes a (non- Air-gap) RPM manifold for every RPM Air-Gap manifold.
There are 4 basic types of dual plane manifolds from edelbrock:
"Performer"
"Performer RPM" (non-airGap)
"Performer RPM Air-Gap"
and let's not forget the one, "Performer Air-Gap".

 

Alright well if you recommend on a mostly street car the non air gap then I will def look into that! thanks all

 

Just so that you all know Im running the Rpm air-gap on my daily driver and it gets down to around -10 or so in the winter and the only problem I had was carb icing. But I have since gone to Tbi injection and have no problems with that at all!!! As for the fuel puddling when at idle, That might happen once or twice in very cold conditions and only when the engine is dead cold and you have not moved yet. After tuning my ecm I have no problems with the air-gap manifold in the cold or at idle and that is with Tbi fuel injection. I personally love it!! Just my thoughts!!!

 

Well I will never let mine touch snow or bad weather so...ahhhhh mixed feedback!

 

What do you want the car to do best? That's what the choice needs to be based on.

 

Exactly.

I dont agree with the "if your car is mostly street driven and rarely sees the strip" part of the argument.

Thats what mine is, and i have an RPM air gap intake. I absolutely love it.

However, my car is only driven from spring, to fall, and parked before the white stuff hits the ground. Except for a few monthly starts over the winter, my car never gets started in the cold.

If i were driving daily, which very few people can afford to do with a small block with price of fuel, or because of the winter driveability of these cars, i would have opted for the regular RPM manifold.

My biggest reasons for choosing the airgap include;

1) Power gain (granted the air gap manifold by itself will not give you a significant power gain, but depending on your combo it helps. It did a good job of not restricting my combo.)

2) Heat dissipation. My car is mostly driven on the streets as a summer cruiser only, and a weekend strip car. My engine runs a tad cooler than it used to, but i also upgraded to headers so its not fully justified.


And lets not forget, it just looks so cool.

 

Run like hell.

But not when there is a puff of smoke/stutter possibility that Supervisor42 speaks of.

Online170, my car is just like yours seasonal wise. I live in Michigan and am parking my car this weekend for the winter (sadly , but I will do whats best)

Do you have any problems with your air-gap in what Supervisor42 says or can verify what hes talking about with other feedback from others who have it?

Judging by my specs of my engine in my intro post, is it a good idea or bad?

 

1987 camaro berl. 2.8 to 357 swap. .510 int and exh lift cam, gear drive, world sportsman 2 64cc heads, 1.5 roller tip rockers, edelbrock performer intake man, 600 cfm edelbrock carb, flat top pistons with four valve reliefs, t5 transmission

Ok, well its hard to say what your cam is. You have a large bore, and 64cc, so you probably have some real torque goin on.

If you ever plan to upgrade to a holley DOUBLE PUMPER carb, its worth mentioning, that the setup will not fit under you hood without modification to the hood.

However, a non-double pumper holley will "just" fit if you have worn motor mounts.

Someone correct me if im wrong, but the RPM air-gap is maybe 1/4" taller than the RPM intake.

That being said, i am after two things with my car in this order:

1) power/ speed.
2) Driveability.

I will compromise alot for more power, like stock looks, fuel, and the occasional puff of black smoke for power, except for driveability.

This means, i want to be able to start my car, and get in and go just like a modern car without thinking twice. Be it a long trip, or a trip to the store.

So if this sounds like you; my answers to your questions are;

1) Do i get the puff of smoke that supervisor is talking about?
Yes i do. When i punch it out of nowhere, there is a puff, but its shortlived and counldnt be a bother. Its not a HUGE cloud, i only know this cuz a freind who was following pointed it out. You get over it quick. There shouldnt be a stutter associated with it. Ever see a drag strip launch? You know how the exhaust is visible off the start but not for long? Its because ALOT of it is being dumped out in a short vecinity, whereas when its moving its spreads out and is not as noticeable. The "puff" is about as bad as that, but its no big deal.

No worse than this: http://www.youtube.com/watch?v=ZP2bWGEYfWA

2) Should you get it?
Well if youre running a 600cfm carb and youre happy with it, i would say you dont REALLY need it. You would probably enjoy the savings from not having to modify anything.

However, if you think you may be upgrading later, and would like those extra couple of hp from the denser charge of fuel, id say go for it.

More than the power, the air-gap's primary function is heat dissipation, and i think it does and excellent job at it.

My engine used to be very restricted, it was setup for tunnel ram, but the previous owner down graded the heads, intake, and carb to all stock q-jet stuff.
So for my combo, i felt the RPM airgap was a nice addition. It complemented the 750 holly and headers nicely. So im very happy with it.

But if youre happy with your combo now, with the power and driveability, id say LEAVE IT AS IT IS, you wont notice a significant change just by upgrading the intake. But if you have a whole new combo lined up thats a diff story.

Hope that helps.

 

The carb pad is the same height from the (insert any engine reference point) on both versions.

The "gap" is produced by lowering the floor into the lifter valley.

 

are you sure? Theres a pretty big thread dedicated to the topic. According to that there was a slight difference in the overall height. My brother has the RPM version on his camaro and i have the Airgap, but i dont have direct access to the cars right now.

I remember reading up alot on the subject and i was sure there was a bit of a difference. Will post the link when i get home.

However i am 100% sure that it (the RPM air-gap) will NOT fit under the firebird hood with a holley Double Pumper. Some modification is required. I could tell you exactly where the issue is if needed.

 

I run a Victor Jr. and a Holley DP and my hood doesn't hit. I have read that the Victor Jr. and RPM Air Gap are the same height. This is with the stock GTA hood, and a drop base air cleaner.

 

Ok well let me clarify a few things here.

I could have made it fit under the hood, if i chose not to run a vacuum line from the intake. On the RPM air gap, it is located about an in. behind the carb plenum, on the "raised" part of the intake. However, on the victor, it is either located in a different spot or not at all (not sure which). After the carb plenum, there is just a drop behind.

So, if i were to run a thin gasket, and plug the vacuum port, i would have been able to do it.

However, i didnt want to drill into the intake a new port, so i chose to use it with an edelbrock low profile fitting.

The "thin" gasket WILL NOT work in this case, as the DP plunger will now hit the low pro fitting, and the carb will not even be close to its mounting position.

As such, i had to either run a spacer, or a 1/4" thick gasket. Since the spacer requires 2 gaskets, the cheaper route for me was to run the 1/4" gasket, and quicker too. (i was pressed for time, i had to catch a plane the next morning).

Using this gasket, the carb is brought up 1/4". A 3" air filter with a drop base air-cleaner base is the samllest filter icould run, becuase i have a choke horn. With the holley though, even if you dont have a choke horn it is still pretty tall.

Now in this format, from front dead center, the filter will hit a "formula" hood and a "GTA" or "regular" hood, in a roughly 60* radius on either side of Front dead center of the air cleaner lid.

I realized after i chopped up my spare hood, that i would have gotten away by simply cutting away the frame of the hood, in this 120* range, and still have been able to retain a stock appearance. However, it would still have been a tight fit, and you have to account for engine torque as well.

Hope that explains a few issues with the RPM airgap.

However, these probs are not encountered with almost any other carb.

 

Five7kid is right- the air gap version of the Performer RPM is the same height as the non-air gap version. Like he said- they drop the "floor" underneath the plenum area lower to create the air space, they don't raise the plenum/carb.

The Vic Jr. is actually about .200" SHORTER than a Performer RPM. This assumes you use the manifold as it comes out of the box. If you put a 1" spacer on it, as is very common in performance applications using that intake then it will, of course, be taller than the RPM.

 

My goal is to upgrade to a better intake and carb. Those two and rear end are on my upcoming list for the winter season, so I was trying to figure out my best bet. I am going with a demon carb I think as of now, and knew I needed a better intake to match so I am figuring out the pair to get.

 

I stand corrected. there is alot of misinformation about these two then, on the site.

According to the edelbrock website, a flat edge is placed on the carb pad stretching from front to back (thermostat location, to dist. location).

The height in the rear is the B measurement, and A is the thermo measurement.

Edelbrock uses a standard formula A+B /2 = height.

For both Performer RPM and RPM Air Gap, they have listed:

A=4.20" and B= 5.25".


Steven, if you plan to upgrade then it seems these two are your best choice. Just need to decide how important the exhaust cross over is for you. For your type of driving though, i dont think it would make a huge difference.

 

From my experieces with the "RPM Air Gap" manifolds:

A) they are the same height as the regular RPM.

B) Cold weather driveability is not any worse than any other manifold, with a properly operating choke. I used my RPM Air Gap all last winter with no problems (and it got down to -56*C a couple times here)

C) The 'Air Gap' is created by lowering the intake base down into the lifter valley. You can see how deep it dips down if you can find a picture of one - normal intakes basically go straight accross between the two heads, the Air Gap base is 'V' shaped if you look at it from the front.

D) This intake is a pain in the *** with double pumper Holleys unless you have room for a carb spacer, or aren't using PCV. The problem is the vacuum port behind the carb base that is meant for power brakes - it will not clear a secondary accelerator pump, even with Edelbrock's "low profile" 90* fitting. Vac Sec carbs will work with that fitting, but not a DP. I plugged that hole and made my own for the brakes (used the carb for PCV).

E) With the right drop-base air cleaner, it WILL clear the hood on both the Firebirds and Camaros. I have the stock hood on my Z28 with this intake, and a friend of mine has a stock hood on his Trans Am with the same manifold as well. Its a very tight fit, but it does fit.

 

Unless you have a double pumper and plan to use the vaccum port on the intake manifold like me.

But as i discovered, its so close that you can get away with just "shaving" away some of the hood's frame, atleast on a firebird.

 

You mean it got down to -68°F where you live? YIKES! What kind of antifreeze do you use? Everything I see is good to -40°F.
Would you care to share the part number and source?

 

-56°C? I dunno about that man, we like to brag about how friggen cold it gets here, but it's not THAT cold. I've only seen -40°C about 3 times in Calgary in the last 5 years, honest temperature. We usually get about 3-4 weeks of intermittent ~ -35°C, and that keeps people inside...

Supervisor, You have to plug in your car anytime it's below -25°C overnight if you want it to start... Or else you'll be fighting it.

 

K&N has a 1.25" drop base PN: 85-3549

And heres a link to another thread that would help you pick a drop base. Thx to FBird-88, you can see how the L-88 drop base fits.

https://www.thirdgen.org/forums/afte...-88#post557085

 

Yes, there were two two-day stretches about a week apart where it got down to -50 something C overnight and early in the morning. I still drove the car to work. I guess its possible I'm remembering the temp including the windchill though... it can get really windy here in the winter.

As for antifreeze... it was about a 65/35 mix. Once antifreeze measures something past -35*C with a tester, it will not freeze easily at temperatures even 20 or 30 degrees colder than that, it will start to gel. The coolant in the cooling system just gets very very thick, but not solid.

As for the air cleaner, I don't know the part number, but its the Edelbrock 14" chromed air cleaner. 1-5/8" drop IRC.

 

the rpm air gap is actually taller than stock making the port runners longer and having a mini tunnel ram effect. while still making good lowend power from the dual plane design.

 

Are you referring to me saying I want to upgrade carb and intake as the two being my best choice? Can you explain the exhaust cross over to me?

 

these two choices; ie:
1) RPM air gap (no exhaust cross over)
2) Performer RPM (with exhaust cross over).

If youve ever seen a stock intake off of the engine, you will see the following "ports" on either side. Starting from the front of the car working back, there is
1) First port, acts as a water jacket for cooling
2 & 3) 2nd and 3rd port are intake runners.
4) 4th port is the exhaust cross over. If you look down it, on the cylinder head part, you would see the number 3,4,5 and 6 cyl exhaust valves. Part of the exhaust gases enter through here, go below the carb plenum, and "CROSS OVER" to the other cylinder head, heating the carb plenum, as damon described.
5&6) 5th and 6th ports are intake runners again.
7) 7th port is for coolant again, but i was told it only has steam coming through it, for when the engine gets really hot. This one can be plugged.


The RPM air gap is missing # 4 and 7 ports.