4 Hole Plenum VS. Open Plenum Question

[Daveh]

Hi Guys,

I ordered some spacers for my small block MOPAR and instead of the open plenum I accidently ordered the 4 hole (See Attached). It's a street engine with an Edelbrock Thunder series 650 carb with a performer intake.  I'm trying to achieve the proper height because they are going on my 71 Challenger with a Shaker hood. Because of their price I want to try to make the correct decision first because if I experiment then I can't return them.


The main question - Will I notice a difference if I use them or should I send them back and get the one hole? Returning them is no problem they told me they will just exchange them. What are your thoughts? Thanks

Dave

[Brads70]

My thoughts are... I'd go with the open one so I don't have to worry about a throttle blade hanging up and keeping the throttle wide open. People often remove part of the divider for more top end anyhow. 

[Cuda Cody]

Maybe @Chryco Psycho  has some experience with this, but I too would opt for the open one in your situation.  But not 100% sure.   

[303 Mopar]

   Your best bet is going with open, but I doubt you will see any major difference in performance since your intake is already dual-plane.

[Daveh]

I just dropped them in the mail to return them for the open plenum spacers.  Thanks guys. 

[HP_Cuda]

Definitely the open plenum, no need to restrict or hang up on anything.

If this was the case you would also use the 4 hole gasket too! 

[GoodysGotaCuda]

Edelbrock clearly recommends the FOUR HOLE style spacer in their carb documentation for low/mid torque and throttle response.


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[RUNCHARGER]

Divided plenum manifold? Yes I think I would have kept the 4 hole.

Sheldon

[HP_Cuda]

Maybe the problem begins with using an Edelbrock carburetor?

[Chryco Psycho]

basically the open spacer will work better in a situation where the engine is under carbed this will allow all four barrels to feed any given cylinder
the 4 hole increases signal to any one venturi & will improve response which helps if the engine is over carbed
a 650 cfm carb is n the small side for any engine except the 318 so the open spacer would be my choice 

[Cudakiller70]

I went with the 4 hole, reading better signal for street. My thinking was if I didn't like it I could cut it open.