notching an intake?

[68RustBucket]

i've read a few places that people have notched their Performer RPM intakes to make them perform similar to a single plane. i was wondering what is involved in doing this. the only difference i see between single and dual plane intakes is that divider that makes 2 barrels of the carb fuel one side of the engine block, and the other 2 fuel the opposite side, so do you just need to remove that divider somehow?

 

[allcarfan]

To notch the intake, you simple cut out the 'divider'. This will make your intake perform like a single plane, but still takes advantage of the extended runner length using the RPM intake.

performer intake is single plane

RPM is dual plane

Victor is single plane

 

[Red Barchetta]

To notch the intake, you simple cut out the 'divider'. This will make your intake perform like a single plane, but still takes advantage of the extended runner length using the RPM intake.

performer intake is single plane

RPM is dual plane

Victor is single plane

Actually, the Performer is a dual plane. The Torker and Victor Jr. are single plane.

68RustBucket, I'm guessing that you have a 289 or 302. Check out Edelbrock's web site for the different styles. Even if you were to completely remove the center divider, it would not be a true single plane intake. If you look closely at the photos from the link, the dual plane intakes actually have two different level "floors" (for lack of a better term) in the plenum.

This photo shows what I'm talking about:

This tries to keep the runner lengths as similar as possible by connecting the far side inner runners with the near side outer runners. In addition, completely removing the divider would probably eliminate this effect, which could result in lower performance.

If you look at the Performer RPM Air Gap, the actually have a slight notch in the divider in the plenum. This might be the best amount to notch the divider.

 

[66P51GT]

Performer RPM Air Gap

Notice the notch in the Air Gap manifold. It is almost the full length of the divider and only about 3/8" deep.

 

[68RustBucket]

alright, so since the Performer RPM has those two different levels, the divider helps utilize the different length runners, and notching it would therefore make the fuel flow unevenly to the heads. please correct me if i'm wrong.
the Performer RPM Air Gap, on the other hand, is already slightly notched and it works well because of the lengthened runners and the more even mixture of cooler air and fuel being supplied to the heads.

i've read plenty of threads talking about clearance issues with the Air Gap and stock hoods. obviously, the Air Gap would increase the performance of the engine overall, no matter how minimal that gain is. does anyone actually know, for a fact, whether or not i'd have clearance issues with my 68 (289, stock hood, holley, edlebrock, or road demon carb) and what the true performance gains could be by using an Air Gap instead of the Performer RPM or even a single plane intake instead of a dual plane?

 

[Red Barchetta]

alright, so since the Performer RPM has those two different levels, the divider helps utilize the different length runners, and notching it would therefore make the fuel flow unevenly to the heads. please correct me if i'm wrong.

That's my guess. Best thing to do is try emailing Edelbrock. Ask them if you were to notch your intake like the RPM, would there be any benifit.

 

[bnickel]

i've seen dyno tests where nothching the divider picks up anywhere from 5-15 hp depending on the combo, however on all of these they only notched the rear part of the divider right under the secondary butterflies, the idea is to make the intake act more like a single plane when the secondaries open, but still provide the benefits of the dual plane under normal driving conditions, which yields better low-end torque and mileage than a single plane intake. however on some really well built HP engines a single plane has been proven to make better overall power even in the low rpm ranges than a dual plane intake. if your motor is stock or fairly mild i would recommend only notching the back part of the divider, if you have a really stout motor you might consider a single plane intake like a vic jr.

 

[mfp4073]

With the trouble you are looking to go through why not just buy a real single plane manifold. I bought an weiand one off ebay 6 months ago for $98. Seems easier and better than trying to convert a dual plane to single...which will never be true single.

 

[jesserose17]

What about throwing in 3/8" or so open carb spacer on performer, so it acts like RPM intake manifold? Wouldn't that be simple solution?

 

[1967coupe]

The Air-Gap and the regular RPM have the same height. This is shown on Edelbrock's website. I have a '67 with the Air-Gap and 600 carb and no clearance issues.

 

[68RustBucket]

why in the world have i read a bunch of different threads that complain about clearance issues with the Air Gap then? maybe it was just my imagination ...
thanks a lot for the help guys

 

[Blue Thunder]

The notch just helps balance the airflow to all cylinders, by letting them "share" venturies. It's not like you're drastically changing the characteristics of the intake, or anything. I doubt you'd even notice the difference at all.

 

[Red Barchetta]

why in the world have i read a bunch of different threads that complain about clearance issues with the Air Gap then? maybe it was just my imagination ...
thanks a lot for the help guys

Not necessarily. The Air Gap and the RPM are the same height only for the 289-302. For a 351W, the Air Gap is almost an inch taller.

 

[slapper]

The notch just helps balance the airflow to all cylinders, by letting them "share" venturies. It's not like you're drastically changing the characteristics of the intake, or anything. I doubt you'd even notice the difference at all.

BINGO !

 

[ratio411]

If you want to get the same effect just to experiment, put an open spacer under the carb and try it. Then if you like it, notch the intake and get your hood clearance back. If you don't see a difference that you like, you have not permanantly altered your intake.

I tend to like mild single plane intakes over the RPM style dual planes myself. To notch the intake or install a spacer is a bandaid for a mediocre intake.

I ran a Torker 289 for years on my mild 306 and loved it. Around 93, when the RPM came out, everyone urged me to get one and 'gain' low end while keeping upper power of my combo. I gave in and bought a brand new RPM. Bad mistake. It stayed on the car about 2 weeks before I got rid of it. By itself, with 1" and 2" spacers, and other mods, I could never get it to come close to the mild SP intake. I gained a tiny bit of bottom end, nothing to get excited about, but lost big time after 3K rpms. Not saying it didn't make power, but it was choked more and more as the rpms went up. A 2" open spacer helped a little, but not enough to worry with, especially considering hood clearance and the simple fact that the SP was better no matter what. Just passing my experience along. The car ran 8.70 in the eighth with no traction using the single plane. 500 extra rpm on the bottom was not what I needed. Heck, I didn't have traction with a 212 @ .050 single pattern cam with a single plane intake. So don't believe the idea that there is no throttle response with an SP. Low end torque gain and high end sacrifice is not what a small cube engine needs.

Sorry so long, good luck
Dave

 

[jesserose17]

Ratio411, Would It make difference if I put in single plane Victor manifold on a 302 engine with stock heads & mild performance cam and hooker competition headers?

 

[taylor4g63]

Do NOT put a victor manifold on a near stock engine...the victor intake is ment for use on pretty heavily built motors. Now, if you want to try a single plane intake, try a MILD one such as the Xcellerator by weiand, or the torker (not torker 2).