Edelbrock and wedge plate

Mike Pass

Supporter
I have recently swapped the 650cfm race carb (6R7950B) on my sbf 302ci for a more road driveable 600cfm vac secondary. I changed over as I had never been able to get it to run well at tick over or low speeds even with fiddling with the changeable idle air bleeds. In doing so I noticed that the wedge plate on top of my Edelbrock Performer RPM dual plane inlet manifold was of the open type more usually used for single plane manifolds. (see pic)
I decided to make a new plastic wedge plate to (a) reduce heat soak into the carb and (b) to have a divider in the wedge plate.
I got a 1” phenolic spacer with 4 holes and milled it into a wedge plate and also joined up the pairs of holes into slots for each side of the inlet. (see pic) The plastic is very, very brittle and I found it would machine best with a small diameter carbide cutter and small cuts.
This would now keep each side of the dual plane manifold separate. However I came across this video comparing the Edelbrock Performer RPM manifold to the Airgap version.

[ame=http://www.youtube.com/watch?v=i2DvnoHWagk]Edelbrock Intake Manifold Dyno Test :: Single Vs Dual + Air-Gap Vs Regular - YouTube[/ame]

In the latter part of the video it compares the standard Performer RPM inlet to the Airgap version and shows that the slot cut into the divider on the Airgap helps the low end performance. I have a new Airgap manifold and can measure the slot size on it. (see pic)
The Airgap is a very good road manifold and has the slot for a reason or is this only going to work for big cams. My 302 has a mild road type cam. I also have a normal 650cfm double pumper (List 4777-4) to try in comparison to the vac secondary in terms of driveability and response.

Question (at last!) is - do I cut a slot in the plastic wedge plate? How big a slot?

Any ideas gratefully received.

Cheers
Mike
 

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  • Ali wedge plate Performer RPM No divider.jpg
    Ali wedge plate Performer RPM No divider.jpg
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    Insulated wedge plate.jpg
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  • Performer RPM Airgap.jpg
    Performer RPM Airgap.jpg
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Mike Pass

Supporter
I have tried it with the original open wedge plate and it works OK. But would it work better still with the full divider or a slot of some kind?
Cheers
Mike
 
I've got the edelbrock 600 cfm vac secondaries 4 barrel and it works really well - there are a few mods to improve them for our cars, pm me and I'll dig them out.
 
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