guys

what is the problem with using a single plane intake manifold for a high perf street car? most guys are running dual plane. I've got a neighbor with a 71 Dart 440 that runs low 11's and he is using a single plane and his car runs fine on the street? I went for a ride with him. I keep hearing about "you need vacuum" for street cars. Well, my car does not have power brakes, and has a manually shifted automatic trans. Why do I need vacuum?

I'm about to dump $250 into a new dual plane Edelbrock Performer RPM manifold because my current dual plane manifold is limited to 5500 rpm, when it occured to me maybe I should be getting a single plane instead.

this whole frickin mess started because my engine loses power above 5500 rpm.

Lee

Are you sure it's the intake and not the valve springs/cam? I have a bunch of used intakes I got along the way to experiment with, and right now I have a Victor Jr on. I'm going back to the RPM soon.

I had a holly street dominator (single plain) intake on my street driven chevelle. It was a dog out of the hole. I replaced it with a performer RPM and it helped alot. A single plain intake will not perform well at lower rpms like a dual plain will. But depending what trans and converter you have in your car this may not be a big deal.

It all depends on the combo. Look at Bob West's combo. What a torque monster!!! 505 with "little" oval port heads, Performer RPM, etc. HERE (http://www.chevelles.com/forums/showthread.php?t=196694&page=2) is a recent posting of his combo.

It is all about the entire package, working together.

From experience a dual plane helps maintain low end throttle response when using too big of a cam. It does this by cutting down on reversion from overlap.

I just went back to a dual plane air gap from a Hurricane single.
My car ran it's best times with the single but I also went from 1-5/8" to1-3/4" headers and from 2.5"exhaust to 3" to 2.5" dr gas X pipe at the same time.
The single made good torque but not nearly as much as the air gap.

The car will start to spin the tires in 2nd while rolling now. That would never have happened with the single.

I think it will help shave off a tenth or 2 off my 60's so the et should drop also.It may lose some mph, but who cares if the et drops.

BTW, my car has a 3000 stall converter in it so that may have helped it.

Lee,

Pull your supposed 5,000 rpm limited intake and cut the divider down 1" and centered 2.5" long and round-off the complete cut and you will definately be able to rpm up to I figure 7,000+ rpm IF your combination is up to it.

A pic of this little modification is shown on page 42 in HPBook's old book, "How to Hotrod Small-block Chevys"....

This used to be done before we had so many newer style intakes to pick and choose from way back then.

I think a 300-36 Holley true high-rise dual plane come's this way out of the box?

pdq67

Or put an open spacer and see what it does. You can then go back or experiment some more.

ok I`ll ask since nobody else has. What is the size ans specs of your motor? What trans, converter and gearing are you running? You don`t want to put a single plain intake on a stock motor, you`ll loose low speed torque. Post your set up and we can help you figure out what the best intake for your motor is.

ok I`ll ask since nobody else has. What is the size ans specs of your motor? What trans, converter and gearing are you running? You don`t want to put a single plain intake on a stock motor, you`ll loose low speed torque. Post your set up and we can help you figure out what the best intake for your motor is.

ok fine:

468 BBC. 10:1 compression, 3.90 gear, TH350 trans, 101 cc Oval port heads (ported and valve job) roller rockers, Comp Cams 11-250-3 hyd flat tappet cam, Weiand Action Plus dual plane intake, Demon 850 dbl pumpr carb, holley high flow mech fuel pump, 2" headers, MSD dist & ignition, 28" tires, fuzzy dice on mirror.

ok fine:

468 BBC. 10:1 compression, 3.90 gear, TH350 trans, 101 cc Oval port heads (ported and valve job) roller rockers, Comp Cams 11-250-3 hyd flat tappet cam, Weiand Action Plus dual plane intake, Demon 850 dbl pumpr carb, holley high flow mech fuel pump, 2" headers, MSD dist & ignition, 28" tires, fuzzy dice on mirror.


I don`t know part numbers like some of the guys here. Whats the cam specs and rpm range? Sounds like a decent street/strip deal. I don`t think I would use a single plain on it though. i would go for a rpm or air gap rpm.

I agree with ZZ69Chevelle, check your springs. I have never seen an intake just stop making power at 5500 rpm because thats the advertised rpm range. If your car truely stops making power at 5500 rpm, then you should begin by checking the springs.

As for the dual plane intake for street use, here's my real world experience. I had a weiand excelerator manifold on my 468. Thats a single plane intake, about 2 weeks ago I switched to a rpm because I got it for a good price and I wanted to see for myself. My car has so much low end torque now I can barely keep the car from spinning the tires at 35 mph. It is amazing the diffrence in low end torque, but I am certain I lost some top end power as well, but my car only goes down the strip a few passes a year so top end doesn't mean much to me. I like to get my heavy car out of the hole and moving.

Jeff

Imho, your Weiand 8005 should pull above 6,000 EASY!!

It's probably the BEST one step up from stock dual plane intake there is out there!!

I figure it beat's a Performer hand's down, jmho.........

pdq67

ok fine:

468 BBC. 10:1 compression, 3.90 gear, TH350 trans, 101 cc Oval port heads (ported and valve job) roller rockers, Comp Cams 11-250-3 hyd flat tappet cam, Weiand Action Plus dual plane intake, Demon 850 dbl pumpr carb, holley high flow mech fuel pump, 2" headers, MSD dist & ignition, 28" tires, fuzzy dice on mirror.

Performer RPM, especially in Chicago....with oil splash tray underneath.

I agree with ZZ69Chevelle, check your springs. I have never seen an intake just stop making power at 5500 rpm because thats the advertised rpm range. If your car truely stops making power at 5500 rpm, then you should begin by checking the springs.

As for the dual plane intake for street use, here's my real world experience. I had a weiand excelerator manifold on my 468. Thats a single plane intake, about 2 weeks ago I switched to a rpm because I got it for a good price and I wanted to see for myself. My car has so much low end torque now I can barely keep the car from spinning the tires at 35 mph. It is amazing the diffrence in low end torque, but I am certain I lost some top end power as well, but my car only goes down the strip a few passes a year so top end doesn't mean much to me. I like to get my heavy car out of the hole and moving.

Jeff

well said Jeff. I'm starting to see the light. seems like 2 out of 3 guys are telling me to stick with the dual plane - so that is what I will do. And yes, I will have the valve springs taken care of then give her another run.

Lee

One small point Harold is ALWAYS talking about!! And that is fuel line SIZE!!

If you have a little, 5/16" fuel line, you just may be starving her!! I hope it is at least a 3/8" line??

Harold is ALWAYS saying that some of his cams need a 1/2" line so please check this too!

pdq67

The biggest difference in single vs dual plane manifolds has to do with airflow dynamics. It is simply the difference between "airflow volume and velocity".. Pro stockers use singleplane manifolds exclusivley, that is bec ause they are able to fully utilize the massive capacity that a single plane manifold affords. For street use the dual plane is usually best because the divided ports cause air to flow with greater "velocity" which translates directly to torque.

One situation where a single plane would be excellent for street use is when combined with a turbo.