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Re: Remove intake divider or not?
[Re: parksr5]
#2277757
03/28/17 03:27 PM
03/28/17 03:27 PM
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Joined: Oct 2007
Posts: 4,209
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,209
New York
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It's a bit of a moral conundrum, yes?
The more specific and detailed they make the rules, the greater the advantage to cheating and the higher the skill level needed to do so.
From another source: "Dual-plane (180º) intake manifolds (only) should have their upper (shallow) plenum dividers cut away between the primary and secondary bores, and a large radius added to the lower edges of the revised opening (where it joins the plenum). Mixture velocity is higher as it hits the floor in the upper plenum due to the shorter distance, which makes the radius more critical. The upper plenum has much smaller volume than the lower, so this closes the gap somewhat." YRMV
Boffin Emeritus
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Re: Remove intake divider or not?
[Re: parksr5]
#2277782
03/28/17 04:04 PM
03/28/17 04:04 PM
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Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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As I recall, when Russ(BSB67) was dyno testing his exhaust manifold equipped 505 on the dyno, he tested several intake and carb combos. One of those was the Indy dual plane. He cut the divider down incrementally, testing each step..... And it kept making more power the more the divider was cut down. In the end I think he ended up removing it completely, which made the best power of all the combos he tested, and that's what went in the car. The performance numbers in his sig speak for themselves. The more specific and detailed they make the rules, the greater the advantage to cheating and the higher the skill level needed to do so. I'm not sure if you're referring the Jim's intake or not, but the way I look at it, his approach to improving the induction system are exactly what the spirit of the rules are about. Reworking a "correct" original part, and have it "appear" unmodified(externally) when done. He applied the same thought process to the carb and heads as well, and his motor made very good power for one of those combos....... Especially considering it also had the added handicap of the pinched down BB Dart drivers side ex manifold.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: Remove intake divider or not?
[Re: parksr5]
#2277865
03/28/17 06:03 PM
03/28/17 06:03 PM
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Joined: Jul 2006
Posts: 4,319
Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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Sorry to simply state the obvious, but Just thinking out loud......, The more I read through this thread, the more it makes sense to me. We here at Moparts have all seen many guys with lots of experience say that Mopar Wedge engines seem to always make more power with more carburetor. The more you throw at them, the more they make. Heck, even Ma threw 1250 cfm at the 440, in the form of the six-pack. It seems to me that opening up a dual plain exposes all cylinders to the whole carb instead of isolating half of it. So in my head it seems that by cutting down the divider, you are not only adding plenum area, you are also effectively adding more carburetion that each cylinder draws from.
I run a box-stock RPM manifold and have long contemplated cutting further into the "slot" that is cast into it. I also just switched out my 830 for a new annular 1000 HP, and to my surprise, throttle response and idle quality seems to not only be better.... it's WAY better. Haven't made any passes yet, but initial feedback is good. Just further evidence of the "more is better" theory. Maybe someday I'll nut up, and go after the plenum of my RPM (???).
Last edited by StealthWedge67; 03/28/17 06:04 PM.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: Remove intake divider or not?
[Re: StealthWedge67]
#2277868
03/28/17 06:10 PM
03/28/17 06:10 PM
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Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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Sorry to simply state the obvious, but Just thinking out loud......, The more I read through this thread, the more it makes sense to me. We here at Moparts have all seen many guys with lots of experience say that Mopar Wedge engines seem to always make more power with more carburetor. The more you throw at them, the more they make. Heck, even Ma threw 1250 cfm at the 440, in the form of the six-pack. It seems to me that opening up a dual plain exposes all cylinders to the whole carb instead of isolating half of it. So in my head it seems that by cutting down the divider, you are not only adding plenum area, you are also effectively adding more carburetion that each cylinder draws from.
I run a box-stock RPM manifold and have long contemplated cutting further into the "slot" that is cast into it. I also just switched out my 830 for a new annular 1000 HP, and to my surprise, throttle response and idle quality seems to not only be better.... it's WAY better. Haven't made any passes yet, but initial feedback is good. Just further evidence of the "more is better" theory. Maybe someday I'll nut up, and go after the plenum of my RPM (???).
Do it! Add a 1" open spacer if you can fit it under your hood. Worked great on my old "509" cammed 440 that ran 11.40s at 3700 lbs. w/ the Edelbrock Performer RPM manifold.
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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Re: Remove intake divider or not?
[Re: parksr5]
#2278089
03/29/17 12:12 AM
03/29/17 12:12 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Years ago, I completely removed the divider and cut 2 notches in both dual and single plane manifolds to where I could put in a slide in divider. Gave me the option of trying infinite divider sizes. Application, carb size, engine size, torque /HP band and range all played in to it - and you get to throw in class rules / limitations. Working on Chevy stuff back then. You can definitely make the factory stuff better. Might cost you $$$$$$$$$$$$$$ in dyno time though. Party down Garth!!
Fastest 300
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Re: Remove intake divider or not?
[Re: parksr5]
#2278129
03/29/17 01:19 AM
03/29/17 01:19 AM
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Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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Removing the divider can definitely numb up the motor down low, but with the bigger cube, high TQ combos......... And the skinny bias ply tires....... That's actually part of the plan.
A lot of what it takes to make a combo run well in FAST is forgetting all the stuff that used to work when you had headers and sticky tires.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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