I was disapointed when I saw that there was two different camshaft profiles used with the dual plane and the single plane manifolds. I think the higher lift, longer duration cam should have been used on all the manifolds. All manifolds peaked out at about 6500 rpm even with the higher lift 7000 rpm cam.  Or even better yet. Comparing both cams with the dual planes to show the possible gains or loses by doing so. Being an old school racer before the single planes came out. I saw a lot of cars in the 10's using high lift cams and dual plane manifolds. Also the selection was great. But I would have liked to have seen the Holley Contender rated at 7500 rpm included. Another interesting twist would be showing the effects of port matching and removing the center divider from dual plane manifolds over an out of the box model.  

im still waiting for my issue. what manifolds were tested?,as i posted a thread last year asking to do a manifiold test just using single planes,as we all know what dual planes work the best.(dont we?)cant wait to read and see how the test came out.  

chevyhipo:
I was disapointed when I saw that there was two different camshaft profiles was used with the dual plane and the single plane manifolds. I think the higher lift, longer duration cam should have been used on all the manifolds. All manifolds peaked out at about 6500 rpm even with the higher lift 7000 rpm cam.  Or even better yet. Comparing both cams with the dual planes to show the possible gains or loses by doing so. Being old school racing before the single planes came out. I saw a lot of cars in the 10's using high lift cams and dual plane manifolds. Also the selection was great. But I would have liked to have seen the Holley Contender rated at 7500 rpm included. Another interesting twist would be showing the effects of port matching and removing the center divider from dual plane manifolds over an out of the box model.

You have to keep in mind we did show one example with both cams with both the dual- and single plane manifolds. This was to give a better idea of what would happen and the numbers revealed it.

Personally, the thing that impressed me was the results of the dual plane Edelbrock Performer RPM Air Gap. We're still planning to see what the limit of that manifold is, so that should be interesting to see.

As for the Contender, we can still do that, however it wouldn't have made much sense in this particular application since the motor was hanging its tongue out before 7,000 rpm.

Thanks for your input and it's already helped to generate additional testing.  

H  

bigcam406:
im still waiting for my issue. what manifolds were tested?,as i posted a thread last year asking to do a manifiold test just using single planes,as we all know what dual planes work the best.(dont we?)cant wait to read and see how the test came out.

Funny thing is, I've always been a fan of single plane manifolds, especially with cubic inches. After the 383 build we did in the August issue and the post results of the manifold testing - I'm sold on the dual planes and plan on using them more often for my street applications.    

You need to become a subscriber to get your issue early bigcam406. But I agree with you about dual planes. The article touched on this. I think it takes a really big cam and hp peaks of 8 grand and up to out perform a good dual plane.  

Yes Henry D there is one good example of the Edelbrock RPM Air Gap with the larger cam shown. I won't give away the figures. But that comparison alone backed my theory of dual plane power. By producing more power with a big cam than single plane titans such as the Brodix and the Super Victor. But it still stayed in character by out torquing every manifold in the test. (That should have them rushing to the news stands. ) Single planes have their place. But I think dual planes rule from 7500 rpm and down.  

the reason i dont subscribe is because it hits he newstands a week b4 i get it in the mail,subscribed a few yrs ago. my opinion is every combination is different,therefore whats good for 1 may not be good for another,thats why we pay these guys the big bucks.  

chevyhipo:
I was disapointed when I saw that there was two different camshaft profiles was used with the dual plane and the single plane manifolds. I think the higher lift, longer duration cam should have been used on all the manifolds. All manifolds peaked out at about 6500 rpm even with the higher lift 7000 rpm cam.  Or even better yet. Comparing both cams with the dual planes to show the possible gains or loses by doing so. Being old school racing before the single planes came out. I saw a lot of cars in the 10's using high lift cams and dual plane manifolds. Also the selection was great. But I would have liked to have seen the Holley Contender rated at 7500 rpm included. Another interesting twist would be showing the effects of port matching and removing the center divider from dual plane manifolds over an out of the box model.

Henry D:
You have to keep in mind we did show one example with both cams with both the dual- and single plane manifolds. This was to give a better idea of what would happen and the numbers revealed it.

Personally, the thing that impressed me was the results of the dual plane Edelbrock Performer RPM Air Gap. We're still planning to see what the limit of that manifold is, so that should be interesting to see.

As for the Contender, we can still do that, however it wouldn't have made much sense in this particular application since the motor was hanging its tongue out before 7,000 rpm.

Thanks for your input and it's already helped to generate additional testing.  

H

I think some testing to find at what point the rpm air gap loses it advantage is needed
How big – heads / cam / compression ratio / cubic inch

I’m currently running an air gap on a 406 with 11.6/1 cr.  200cc sportsmen heads and a .645 lift roller
Car weight 2775 w/d and runs 10.20 center divider has been cut down to clear spay bar and with
150 shot ran 9.70  shifting at 6200 pump gas
Needs more heads and less cam but these parts are paid for  

well, i finally got my issue.great job guys! justa few thoughts....the engine combination you used was in my opinion a max street effort,thats why the air gap posted great numbers,amongst other dual planes as well.there just wasnt enough motor for the single planes to shine,mind you,my biggest shock was to see the bowtie intake post the highest averages,yet after going over the torque and hp chart,showed it made up most of it after 5000 rpm.my biggest disappointment was the brodix sp-1,i thought it would perform better,since it was matched with those brodix heads.me thinks you should build a 406-421,high compression roller motor to really see what these single planes have to offer.  

bigcam406:
well, i finally got my issue.great job guys! justa few thoughts....the engine combination you used was in my opinion a max street effort,thats why the air gap posted great numbers,amongst other dual planes as well.there just wasnt enough motor for the single planes to shine,mind you,my biggest shock was to see the bowtie intake post the highest averages,yet after going over the torque and hp chart,showed it made up most of it after 5000 rpm.my biggest disappointment was the brodix sp-1,i thought it would perform better,since it was matched with those brodix heads.me thinks you should build a 406-421,high compression roller motor to really see what these single planes have to offer.

Thanks for the kudos, bigcam. I think you nailed a lot of things right on the head. First, I like your "max street effort" title for the engine we used. The thing is, more than a few guys who build this type of motor stick single planes on them--myself included, or rather I would have before this exercise. Now you know why the piece was titled "Manifold Learning." That's why we test, to find out what's what. And as for your observations on what type of motor we need to really give the single-planes a workout, well, I think I can safely say that we're all on the same page on that one.
JN
And by the way, I'm gratified that you went through the dyno charts so thoroughly...'nuff said.  

ty for your kind words sir....  

Henry D, I am having a tough time digesting the numbers here. Is the AIR Gap different in specifications than the Perfomrer RPM? I think I spoke to Edelbrock and the port heights and dimensions are the same.

I ask because I did A-B-A testing at the drag strip with my car between the Performer RPM (non air gap) and the Vic. Jr. I logged all variables and corrected all times to sea level. I found that the dual plane was only .02 quicker in the 60'. The single plane made up the difference by 330' and in the 1/8th the single plane was .05 quicker and 1.5 MPH faster.

According to your test results the dual plane should have been much quicker on the 60' and beat the single plane throughout the whole run. Obviousely, my results were quite different.

Combo: 3450lb. 69 Camaro, 406, AFR 195s, Performer RPM Cam (234/244,.488/.510). I had 3.73 gears and a TH350 with a 4200 RPM stall. I shifted at 5900.

What am I missing? If the AIR Gap is better than the "old" RPM then that would explain it. Otherwise I am confused.

Thanks!  

your cam and convertor are at opposite ends of the scale.that cam works from approx 2500-6500,yet your stall is 4200.all your low end torque that the dual plane is producing is nullified by the slippage of the convertor.if you used a 2800-3000 convertor with that cam and intake,the results with the performer intake would show a definite improvement over the victor jr.justa thought,hope it helps...  

bigcam,

Your are hitting on my point except for one thing...if you read the test results in the magazine, the Performer RPM beats the Vic Jr (not Super Victor) at EVERY RPM. It beats it down low, it beats it in mid range, AND it beats the Vic Jr on the top end too. Check over the numebers carefully. That's why I am skeptical of the test numbers.

My MPH and et gain with the Vic Jr tell me it's making more power up top than the RPM. I only shifted at 6,000 and it falls back to 4600.  

the reason why your combo is making more power upstairs with the victor jr. is because of the AFR 195'S you are using compared to the test motor Brodix's IK 200.the AFR's have a much better port design and flow alot better than the Brodix;s,you probably already know this anyways.if u change that cam to a 106-108 lobe center instead of the 112 that u are using now the difference will be even more obvious.basically,the test motor had an ok head with a good intake(victor jr.)and your combo has an excellent head with a good intake.these things make a difference.