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View Full Version : Intake: RPM air gap or Victor JR


MYBAD79
05-23-2009, 01:19 AM
Just wondering: a stroker (383ci) can take a lot more cam than a 350, is the same true for intakes when it comes to advertized rpm range ?

My cam is a Comp roller with 230-236 dur and .510/.520 lift. I can't complain about the low rpm torque, it feels pretty good from idle to 6000 as it is right now with the good ole "performer" intake....

Am I going to loose a lot of low rpm driveability with a Victor Jr intake that is advertized at 3000-8000rpm vs. a RPM air gap that is advertized at 1500-6000rpm ???

The RPM is almost $100 cheaper in the polished version so it would be hard to justify the Victor anyways .... hood clearance is not an issue with the L88 hood.....again: just curious....

big_G
05-23-2009, 02:50 AM
I don't think a 383 will lack torque down low. That said, I think the top-end benefit of a single plane out-weigh the small increase in bottom torque that the performer RPM would bring.

On a side note...since going to fuel injection, I have a couple of Vic. Jr. intakes collecting dust that I could deal on.

MYBAD79
05-23-2009, 03:29 AM
I have seen many threads and ads about how awesome the rpm air gap is but I am afraid it might be just the advertisements.....

I saw a cheap Victor Jr in the local Craigslist not too long ago.... should have bought it I guess.... at the time I thought a dual plane would be a better fit... oh well....

Anybody with a Victor intake on a 383 ???

How much can a intake change the characteristic of an engine anyways ???

hbz_81_c3
05-23-2009, 01:39 PM
I can't speak on the Victor Jr.although I would like to try one. (Big G PM sent) I have the RPM airgap on my 383 and it is a good combination for normal driving. The only draw back is that it does begin to nose over just around 6000 rpm. I am running a bit more cam with a 288 comp roller. What carb are you running? I believe for a all around manifold the RPM Air Gap is going to be hard to beat. The loss of low end on the Victor may be well overcome by the gains upstairs.

lars
05-23-2009, 08:19 PM
I've run a Victor Jr on a 357 on the street with a modest cam, and there is nothing wrong with low rpm torque. The car would melt the tires from 2000 rpm up through my 6500 redline, and it wanted to keep going... I believe most of the "bad low rpm torque" comments come from people who don't know how to tune and set up the carb and ignition and from people who don't know how to downshift...
Lars

MYBAD79
05-23-2009, 08:33 PM
That's the first hand experience I was looking for. :thumbs:

The polished Victor is $411 :ill:

big_G
05-23-2009, 10:17 PM
I've run a Victor Jr on a 357 on the street with a modest cam, and there is nothing wrong with low rpm torque. The car would melt the tires from 2000 rpm up through my 6500 redline, and it wanted to keep going... I believe most of the "bad low rpm torque" comments come from people who don't know how to tune and set up the carb and ignition and from people who don't know how to downshift...
Lars

Exactly. So now we can add :"90% of intake manifold problems are ignition or carb. problems"...:drink:

MYBAD79
05-26-2009, 02:34 PM
Found this comparison at SuperChevy:
[Only registered and activated users can see links]

Interesting:
[Only registered and activated users can see links]


I have to keep in mind that in 5th gear at 60mph I'm at around 1800rpm, I can't give up too much low rpm grunt or I'll be constantly shifting between 4th and 5th gear at 50-60mph....

big_G
05-26-2009, 03:19 PM
Found this comparison at SuperChevy:
[Only registered and activated users can see links]

Interesting:
[Only registered and activated users can see links]


I have to keep in mind that in 5th gear at 60mph I'm at around 1800rpm, I can't give up too much low rpm grunt or I'll be constantly shifting between 4th and 5th gear at 50-60mph....

Looking at the graph above, the rpm range you will cruise at shows <15 lb./ft torque loss. Fairly insignificant, IMO.

Twin_Turbo
05-26-2009, 03:23 PM
Yes, but look how well the airgap keeps with the victor in the higher rpms, so apart from bragging about having a victor, I would stick with the airgap. The victor is a lot taller than the airgap so there's another benefit.

big_G
05-26-2009, 04:03 PM
Yes, but look how well the airgap keeps with the victor in the higher rpms, so apart from bragging about having a victor, I would stick with the airgap. The victor is a lot taller than the airgap so there's another benefit.

Well, it kept up until 4,700..hardly what I would call higher rpm's. I also noticed that the engine combo. used for the test is all out of wind at 5,500 rpm's. Not what I would call "Home field advantage" for the Vic. Jr. It is more suited on an engine that spins to 6,500.

MYBAD79
05-26-2009, 05:02 PM
The Victor Jr intake was even ported.... I noticed they also tested the temperature difference between the air gap and no air gap manifolds... once I find a good test RPM vs. AirGap THAT might bring the Performer RPM back in the game.... $270 for the polished version is $140 less than the Victor...

Twin_Turbo
05-26-2009, 07:36 PM
Yes, but look how well the airgap keeps with the victor in the higher rpms, so apart from bragging about having a victor, I would stick with the airgap. The victor is a lot taller than the airgap so there's another benefit.

Well, it kept up until 4,700..hardly what I would call higher rpm's. I also noticed that the engine combo. used for the test is all out of wind at 5,500 rpm's. Not what I would call "Home field advantage" for the Vic. Jr. It is more suited on an engine that spins to 6,500.

I know but even above 5500 the difference isn't all that much, how much of the time do you drive @ over 5500 rpm? See, bragging rights is nice and all but for a street car the airgap is a damn good manifold.

MYBAD79
05-26-2009, 07:57 PM
I know but even above 5500 the difference isn't all that much, how much of the time do you drive @ over 5500 rpm? See, bragging rights is nice and all but for a street car the airgap is a damn good manifold.

I tried to find some real world comparisons between the RPM and the AirGap but didn't find much useful on the net....

Right now I have the good ole "performer" so pretty much anything would be an improvement.

big_G
05-26-2009, 10:27 PM
Yes, but look how well the airgap keeps with the victor in the higher rpms, so apart from bragging about having a victor, I would stick with the airgap. The victor is a lot taller than the airgap so there's another benefit.

Well, it kept up until 4,700..hardly what I would call higher rpm's. I also noticed that the engine combo. used for the test is all out of wind at 5,500 rpm's. Not what I would call "Home field advantage" for the Vic. Jr. It is more suited on an engine that spins to 6,500.

I know but even above 5500 the difference isn't all that much, how much of the time do you drive @ over 5500 rpm? See, bragging rights is nice and all but for a street car the airgap is a damn good manifold.

I think you missed my point, TT. The engine used for the comparison was not capable of higher rpm's..giving up just when the Vic. was coming on, therefore giving the advantage to the dual plane intake.

Spooky
05-29-2009, 04:06 PM
I recently switched from the victor jr to the air gap on my big block. A couple grains of salt before we get started, I haven't raced either manifold, and so far I've only had a couple of good days worth of driving with the air gap.

My first impression of the air gap was 'This is how the car was supposed to feel.' It is now much easier to drive. It starts easier, idles better, and the power comes on smoothly. My biggest complaint with the victor jr was that it did not like running at slow speeds. In town, stop light to stop light it was a real pain. The victor jr would stumble when attempting a "civilized" start from a stop, and would stall during hard braking.

The Air Gap cured all of my complaints about the drivability, and I would definitely recommend it for a street car. The seat-of-my-pants-o-meter indicates I have given up a small amount of power. However, to me it is a small loss when compared to the gain in ease of operation.

MYBAD79
05-30-2009, 12:26 AM
wow, I did not think just a simple intake swap can make such a difference. Just to make sure: you did not change anything else ?

I'm really looking forward to this intake/carb swap, after all this I think the Edelbrock 800 cfm carb and the air gap intake will really wake this engine up....

guru
05-30-2009, 02:29 PM
Intakes are just like headers, the runners need to the appropriate length and the plenum has to have enough volume.

The airgap has long runners and a hole in the divider to increase the effective plenum size. The increased plenum size benefits the top end and the longer runners help it down low.

A single plane will have a large plenum, and shorter runners making it better for the top end.

The question is will you have the torque available.

Driveshaft
06-01-2009, 03:50 PM
I tried to find some real world comparisons between the RPM and the AirGap but didn't find much useful on the net....

Right now I have the good ole "performer" so pretty much anything would be an improvement.

If you see dyno tests the air gap will make more power, but that is on a nice cool engine in a dyno room.
When you actually drive the car with a closed hood, the air gap is not going to make as much difference because both intakes will essentially be the same temp then, and cooler runners is the only advantage of the air gap over the standard RPM. If you run a valley tray under the standard RPM intake I doubt you will ever notice the difference.

Spooky
06-01-2009, 06:08 PM
Just to make sure: you did not change anything else ?

Nothing else was changed other than re-tuning the carb.

MYBAD79
06-05-2009, 02:14 AM
Based on the following (from this thread):
- how much of the time do you drive @ over 5500 rpm?
- My biggest complaint with the victor jr was that it did not like running at slow speeds. In town, stop light to stop light it was a real pain. (this on a Big Block)....
- The victor is a lot taller than the airgap (I'm concerned it might not fit with 3" filter although I have a tall hood)

and

- price ($411)
- I don't think my Edelbrock RPM heads are a good match for a Victor intake ...

I ordered the RPM air gap... even if both intakes perform about the same up to 6500rpm - the air gap is $100 less.

I also ordered the 800cfm Edelbrock carb with the adjustable secondaries... can't wait to install and test drive... :devil:

I'll soon have a Performer intake and a 600cfm Performer carb for sale, very good condition, like new.... IMO a good combo for a stock/mild 350.....

Shurshot
06-08-2009, 10:24 AM
I did some testing a couple of years back on a solid roller 496 between the Vic Jr. and a Brodix dual plane that had already proven itself better than the Air-Gap.

At 7000 RPM the Vic Jr. was making 8 HP more than the Brodix 2018 dual plane that started to loose it first HP going past 6800 when they were even. Giving the Vic Jr. its due credit it was not far off from the Brodix torque numbers down low...... actually surprisingly close and it MIGHT have continued to pick up more beyond the 7000 self imposed red line.

However the performance of the Brodix dual plane was so good and because along with its huge runners it fit without any hassles I chose it (the vic jr. would not fit on a BB under the 66 BB hood)

Two years later and in hindsight I am still fond of the Brodix and consider it to be the best dual plane bar none however using any dual plane that by design has a shallow plenum floor on a high rpm big motor (over 454) is not something that I would do again.

This time around on a 540 I am using a milled single plane but on a 383 I would go with the Brodix and get the best of both worlds along with an easy fit. On a side note the Brodix is a flat parallel to the crank intake so exact float adjustment is much more critical.

Doug