I looked in the catalog and I think there is more to the Edelbrock "air gap" manifold than grinding down the plenum. If you look closely you will see that it doesn't have a heat crossover passage at all. And the air gap they are talking about is underneath the runners of the manifold.

 

[font size="1" color="#FF0000"]LAST EDITED ON 24-May-01 AT 08:25 PM (EST)[/font][p]Well, yes, there is more to their "air-gap" intake then just the modified plenum, its basically a higher rpm intake thus the larger, raised runners. You are incorrect about the air-gap refrence. It does refer to the gap in the divided plenum, thus performing as a dual plane at lower rpms with some of the benefits of an open plane at higher rpm. The air-gap does not refer to the raised runners. Numerous high performance intakes have that space below the runners and they are not called "air-gaps". Just an FYI. Oh, and, the Edel RPM intake doesn't have the exhaust crossover either. You can still make your Edel RPM intake into an "air-gap" with the accompanied benefits. The only difference beween a modified RPM intake and the actual Edel air-gap intake is that a modified RPM intake would be more effective in the rpm range of a truck, whereas the "actual" air-gap intake will shine at higher rpms in lighter vehicles.

If your knuckles ain't bleeding you did something wrong.

'72 F-250 "Hi-Boy" 4x4, Dana 60/HD44, FE428 @ 400 ponies , 4-speed, custom suspension w lift, mud on black.

 

One of Edelbrocks ads for the air gap intake had an arrow pointing thru the area between the runners and the base of the intake and they talked about how running air below the runners helped to cool the intake and would give a colder denser charge. That's what I've always thought of the air gap as. The new Victor FE intake is made that way and I've seen some other FE intakes with that design but not too many main stream ones.

I didn't give much thought to cutting down the partition below the carb although I have seen many intakes designed that way. What's the main benefit of this?

 

[font size="1" color="#FF0000"]LAST EDITED ON 25-May-01 AT 01:04 AM (EST)[/font][p]The reason for the extended runners is that it moves the rpm band up. That design is really great for the top end, but is awfull for bottem end torque. It only helps for cooling off the fuel/air charge marginally due to the conductive properties of aluminum. These types of intakes actually abound, and have been around for a long time. They range from mild all the way to tunnelram, where they stick waaaay up there. Due to the info you've revealed about edels ad, I suppose in this case they could be referring to the raised runners as the "air-gaps". I find that a bit silly if thats the case though, as these types of high rise intakes have been around since the sixties, and typically "air-gap" is referring to the plenum diveder modification. As to your question, that mod allows both heads to draw off the entire carb at higher rpms (to a degree), much like an open plenum, without sacraficing the low end torque like you would with an actual open plenum manifold.

If your knuckles ain't bleeding you did something wrong.

'72 F-250 "Hi-Boy" 4x4, Dana 60/HD44, FE428 @ 400 ponies , 4-speed, custom suspension w lift, mud on black.

 

I went to the Edelbrock website and copied this. I guess the main difference from older style victor type manifolds, is this one has the air gap underneath and is dual plane too.



PERFORMER AIR-GAP (idle-5500 rpm)
Designed for 1955-86 262-400 c.i.d. small-block Chevys, the Performer Air-Gap features the air-gap design for the ultimate street performance in the idle to 5500 rpm range. This design features an open air space that separates the runners from the hot engine oil resulting in a cooler, denser charge for more power. High-velocity runners deliver excellent throttle response throughout the power band. The great looks of the Performer Air-Gap along with the solid idle to 5500 rpm performance makes this an ideal choice for street rods and street machines. No provision for exhaust heated chokes or exhaust crossover. For spread-bore or square-bore carburetors without adapter. Available with standard finish or polished.
Performer Air-Gap (non-EGR) #2601*
Polished Performer Air-Gap (non-EGR) #26011*

Here's the link:

http://www.edelbrock.com/automotive/index.html

 

That's the intake I wish they would have made instead of the Performer RPM for the FE. I have a Performer RPM for my 428, and it looks like it could have enough room to make an air gap but for some reason Ed didn't do that. Your right about this being around in the sixties, and the only Ed intake that offers this is the Victor and that has a VERY high rpm range.

Oh well...

 

[font size="1" color="#FF0000"]LAST EDITED ON 26-May-01 AT 03:55 PM (EST)[/font][p]Well Franklin, it looks you are right, Edel is referring to the high rise design rather than the plenum design. My mistake. I still think this is silly, as this runner design is nothing new and that type of plenum divider is typically called an "air-gap" design. What I really don't understand is how this can be an "off-idle" intake. These type of intakes always have a much higher rpm operating range, and they're rating it lower than the performer rpm!? Intake design and theory is one of the things I know a little about and this makes no sense to me. I've never gotten a good look at one of these new suckers before so I guess I'm going to have to check it out. I also still contend that your not going to get much cooling benefit from slightly raised runners due to the conductive properties of aluminum, unless you don't run with a hood or fenders. In otherwords Karljay, I don't think your missing much and the Performer RPM is a great intake. But again, I guess I'm going to have to take a closer look at it.

* I just followed the link and looked at it, and had to come back to edit this. The pic of an Edlebrock "air-gap" intake I saw in Summit wasn't like this one (probably wasn't even a Ford intake), I see this one doesn't even have the modified plenum divider like the one I saw! No wonder I had you guys confused. I'm not all that impressed with what I saw, to be honest. Oh, and it says it has the same operating range (1500up) as the rpm, not off-idle. Sorry about the mis-understanding guys, but the plenum divider mod is still a good trick for your intakes.

If your knuckles ain't bleeding you did something wrong.

'72 F-250 "Hi-Boy" 4x4, Dana 60/HD44, FE428 @ 400 ponies , 4-speed, custom suspension w lift, mud on black.

 

-replying to someone who said that it would be great if someone made a forged steel crank for FE's-

Actually Scat makes several forged billet cranks including strokers. Oh, I must have missed the affordable part, These things are way past a grand.
Edelbrock only makes on set of heads for FE's, they are RPM.
Genesis is coming out with Iron and Aluminum blocks for FE's.
Shelby already makes them(for a price)
The victor intake is not out yet, not for low rpm anyway so don't worry.

Sometimes if you don't run an exhaust crossover in cold weather your engine wont heat up!
With my low compression FT engine, this was the case.
With my new high compression FE it warms up instantly(all the extra power makes more heat) This is where you really see the advantage. It is not a good Idea to block the crossover in all cases.