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Author Topic: 4 Hole Plenum VS. Open Plenum Question  (Read 174 times)

Offline daveh

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4 Hole Plenum VS. Open Plenum Question
« on: February 03, 2017 - 09:51:20 AM »
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




Online burdar

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #1 on: February 03, 2017 - 09:56:09 AM »
The only thing I'll say is that the secondaries are larger on the carb you have.  If you use the four hole spacer, make sure the secondaries clear the spacer opening.

Offline Road_Runner

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #2 on: February 03, 2017 - 02:13:26 PM »
When I've used one I always used an open one, from what I've read this style tends to be better for top end much like grinding down the center divider on dual plane intakes, etc. 
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Offline Mopar73340

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #3 on: February 03, 2017 - 03:55:32 PM »
I like the four hole on the street. It tends to show more signal to the carb and seems to lend to better low end response. I am also using it on an Edelbrock 650 and 800 carb. Like said just make sure ALL butterflies clear and don't bind before driving it.
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Offline Aussie Challenger

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #4 on: February 03, 2017 - 04:34:11 PM »
I like the four hole on the street. It tends to show more signal to the carb and seems to lend to better low end response. I am also using it on an Edelbrock 650 and 800 carb. Like said just make sure ALL butterflies clear and don't bind before driving it.
I agree the butterflies are the only thing needed to check, at least you can assemble and check if the engines performs to your expectations, if not it doesn't take much to remove the centre section and turn it into an open spacer. Street needs a strong signal at the carb base.
Dave

Offline Cudakiller70

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #5 on: February 03, 2017 - 10:41:29 PM »
That looks like it's from cool carb?
I got the 4 hole, I've read too better carb response for street  :dunno:  I figured if I didn't like it I'll just cut the center  out  :clueless: :dunno:
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Offline solarguy

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Re: 4 Hole Plenum VS. Open Plenum Question
« Reply #6 on: February 04, 2017 - 09:11:40 AM »
I have a 4 hole 1/2" phenolic spacer under my 625AFB on my stock intake 340.  It really helped insulate the carb and increased off idle throttle response.