performer plenum divider

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Wink-o-kid
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performer plenum divider

Postby Wink-o-kid » Fri Aug 11, 2017 7:31 pm

has anyone ever machined out the plenum divider on a performer (non rpm) to gain top end flow?
the engine is a original to the car 396,
10.0 :1 forged
edelbrock rpm ovals
870 holley street avenger
comp hyd extreme energy
owner wants to run stock hood, performer is the only choice to clear.
in the old days we used to cut out the divider in the old gm dual plane to gain some upper rpm flow
is this still the way to go?

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Re: performer plenum divider

Postby F-BIRD'88 » Fri Aug 11, 2017 7:59 pm

This is not your only choice. If you need a low carb height to fit under hood,
get the factory OEM 1971 GM LS6 454 rectangular port low rise dual plane intake. The low rise version that was on the 70-72 396 Camaro and 71 454 Vette.
Bolt it on the oval port heads. Ignore the port mismatch.
Before reducing the plenum divider try a open spacer on that intake for effect.
( avoid reducing the plenum divider on this intake as it is worth a good buck.
use a spacer)
Be sure to use the correct era OEM GM air cleaner to max hood clearance.
Is this a 70-72 Camaro?

More hood clearance.
More power than the BBC performer intake.
Do not sweat the port mismatch just bolt it on.

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Re: performer plenum divider

Postby Wink-o-kid » Fri Aug 11, 2017 8:03 pm

this is a 66 chevelle

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Re: performer plenum divider

Postby Wink-o-kid » Fri Aug 11, 2017 8:08 pm

i tried to talk the owner into a 427 or a 496, but he wanted a 396!!!

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Re: performer plenum divider

Postby BOOT » Fri Aug 11, 2017 9:15 pm

Try an open spacer even if you gotta run it w/o the filter real quick and if it likes it then notch the divider.
I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!

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Re: performer plenum divider

Postby F-BIRD'88 » Fri Aug 11, 2017 9:16 pm

The Performer RPM air gap BBC intake will fit under this hood with the correct GM air cleaner
You got the wrong air cleaner...
There is no reason to just the lowly performer manifold on this motor in that car.

The factory 66 396-375HP L78 motor had a Hi-rise Dual plane intake and this correct air cleaner
Thats why it fits... It is the air cleaner BASE.
Get this correct GM OEM 60's era Air cleaner base and cut the choke tower off your (Non OEM) holley carb.

If you swapped his 396 for a simple oval port 496 BBC he would be "converted"
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Re: performer plenum divider

Postby F-BIRD'88 » Fri Aug 11, 2017 9:22 pm

A 2 by 4 across the back of the head will fix his silly 396 fetish.

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Re: performer plenum divider

Postby bigjoe1 » Fri Aug 11, 2017 9:27 pm

DO NOT USE the GM low rise manifold - It was 25 hp LESS than the L-88 dual plane



JOE SHERMAN RACING

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Re: performer plenum divider

Postby F-BIRD'88 » Fri Aug 11, 2017 10:03 pm

bigjoe1 wrote:DO NOT USE the GM low rise manifold - It was 25 hp LESS than the L-88 dual plane



JOE SHERMAN RACING



Yes the L88 OEM intake is going to be better but the low rise LS6 intake will still be better than the lowly Performer BBC intake annd gets even better as you add carb spacer to it.
The low low height and air cleaner allow for this..

But on this car there really is no need to mess with this as the Performer RPM hi rise will fit
this car as the 427 L-88 intake would too.

it would be interesting to see the dyno difference between a modern RPM air gap against the GM 427 L88 OEM manifold (even wit the port mismatch)

Another great option is the 2x4 Dual Quad RPM intake. It should also just fit under this hood But WILL REQUIRE a Custom made air cleaner.
The lower C-66-O low rise dual quad will fit with ease and also allows carb spacer height play too. Again a correct custom built air cleaner is required for this...

With the stated Comp Extreme energy Hyd cam on this motor The 427 L88 intake true top end HP capability will not really be realized as the cam in this motor will be the choke.

All these are more powerful choices over the Performer intake.
The performer intake should improve with spacer too.
The correct air cleaner may allow this.... Then get the hi rise RPM intake.

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Re: performer plenum divider

Postby F-BIRD'88 » Fri Aug 11, 2017 10:59 pm

If you are going to play with carb spacers on the performer intake try a open spacer, then try a COMBO spacer...The 2 hole side goes on the deeper side of the plenum. The open oval side goes to the shallower side of the dual plenum.
taking out the whole plenum divider will probabily be a big mistake on this car
if it does not have a race converter. Max it out with the spacers first.
Then, like I said just get the Perf RPM hi rise intake .

you can make your own COMBO spacer out of wood if you want.
Wood makes for a very good carb spacer material. Best on a BBC if when combined with the Holley style carb heat shield. GM used to sell these at the parts counter for these cars back in the day.

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Re: performer plenum divider

Postby pdq67 » Fri Aug 11, 2017 11:26 pm

Or you might hunt up an old Weiand 8005 large oval port dual plane intake.

It is Weiand's version of the old E-Brock BBC oval port Performer and just looking at one will tell you that it is a much, "healthier", looking intake than the Performer, imho.

I originally bought one from Summit back years ago, but took it back and switched to a large oval port Holley Strip Dom. single plane.

Wished I would have kept it as well as used the Holley. The Holley is on my 496 now.

pdq67

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Re: performer plenum divider

Postby mag2555 » Sat Aug 12, 2017 5:16 am

I single plane Holley street dominator may fit , plus work better in terms of top end if you or the owner can turn one up.


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