skinny z

Came across a great video comparing Edelbrock's Vic Jr., Rpm Air Gap and Performer RPM manifolds.
They got to the point of using a 1" open spacer on the Performer and showed the results but didn't put the spacer on the Air Gap. It was said in the video that the Air Gap with the spacer WILL make more power but there's no dyno sheet to show what happens to low and mid rpm torque and horsepower.
Does anyone have an experience or know of any testing done that can support this?
I'm all for a little hp at the top end when I'm racing but I don't want to kill my drivability or fuel economy doing it.

DeltaElite121

With a proper converter, gearing, and camshaft (like anything else car related; PAIRING) - you will not lose any drivability with a single plane, and start progressively gaining a lot over the Airgap from about 4500+. Victor JR is a poor comparison to a good single plane, IMO.

Airgaps don't push very much air, and thus cannot support the bigger horsepower even if it's readily available. You could change that if you get someone like Bryce @ Dr.J's, but you're just under $900 for a dual plane at that point, and I don't know how I feel about that.

If you don't even wind the motor up to 6K RPM's then the Airgap is definitely the way to go, though. Port match, and be done with it.

skinny z

At this point my selection of compatible parts is done. That is until something lets go and I have to replace it. This is an everyday car that I beat up at the dragstrip now and then (next year I'll be in bracket series though) and I take as much pride in my highway fuel economy as I do a decent time slip. Which by the way, at 3650 lbs is 12.6 at 108 mph (with fueling issues that put the AFRs WAY off at the top end.)
As you point out, with a better converter, gearing and another cam, I could probably get into the 11's. If this transmission lets go, I'd look for something with a close ratio gear selection. Our testing has shown that this alone is worth a couple of tenths in a vehicle like mine.
That said, getting back to my original question, I was looking for an easy few horsepower. The spacer is simple enough and cheap too. What I don't want is to lose the low and mid engine speed torque that this car thrives on. I'd need some dyno evidence before I made a decision.
This engine is making peak power at or around 5700 rpm. I stretch it out a little on the 1-2 shift because of the 700R4 gear ratios. It seems the Air Gap is my best choice as you've said. I'm just looking for a little more.

cuisinartvette

There is no way to know without trying one
Some benefit and others run better without one.

Street/strip cars usually run best overall with a dual plane; think the RPM is around 270x cfm but may want to call Edelbrock and verify

Just know cfm with intakes isnt THAT critical its just a way to measure thats accepted in the industry. On a running engine it isnt moving a steady column of air such as a flowbench. IMO on a longer runner intake then the cfm thing becomes more important

Let us know what results you get.

skinny z

True enough. It's interesting to note how the characteristics of the plain Performer changed when the plenum divider was milled down to replicate the Air Gap divider. They also managed to bring the peak horsepower numbers within a few of an unmodified Air Gap. To listen to the video, it's stated that the Air Gap WITH a spacer will definitely make more power too. The drivability/fuel economy issue never came up of course.
This is something I'll experiment with next season. I'm moving across the country and one of the upsides is an IHRA sanctioned drag strip 25 minutes from the house. Plenty of time to experiment.

DeltaElite121

Air gap moves low 210's to mid 220's CFMs. Most single planes move low 280's without any work and end up in the 290's to 300's with just a port match. Keep in mind you lose about 10% of that volume from transition to the cylinder heads. On most aftermarket heads the air gap will pose a restriction on power potential.