Milling down the divider of the intake, yes or no?
#1
Pro
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Milling down the divider of the intake, yes or no?
Hi!
I´m in process to exchange the stock intake mainfold to a LS6 intake (and AED carb) of my 489ci stroker BigBlock. I read several times that milling down the divider would gain some HP and TQ. Would you recommend me to mill it down or not? Max. rpm is about 5500-6000.
Thank you, Günther
I´m in process to exchange the stock intake mainfold to a LS6 intake (and AED carb) of my 489ci stroker BigBlock. I read several times that milling down the divider would gain some HP and TQ. Would you recommend me to mill it down or not? Max. rpm is about 5500-6000.
Thank you, Günther
#2
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St. Jude Donor '05
Id leave it be and get a bigger intake if you want more...youll get a better signal to the carb not cutting it out
It never helped any of mine but did notice my idle/tip in quality suffered some.
It never helped any of mine but did notice my idle/tip in quality suffered some.
Last edited by cv67; 01-15-2019 at 04:34 PM.
#3
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Hi!
I´m in process to exchange the stock intake mainfold to a LS6 intake (and AED carb) of my 489ci stroker BigBlock. I read several times that milling down the divider would gain some HP and TQ. Would you recommend me to mill it down or not? Max. rpm is about 5500-6000.
Thank you, Günther
I´m in process to exchange the stock intake mainfold to a LS6 intake (and AED carb) of my 489ci stroker BigBlock. I read several times that milling down the divider would gain some HP and TQ. Would you recommend me to mill it down or not? Max. rpm is about 5500-6000.
Thank you, Günther
#5
Le Mans Master
If you have the hood clearance you could try a thick open gasket under the carb first maybe 1/2 “ or so, see if you like the results.
#6
Drifting
The Weiand Stealth intake I have on my 454 has the divider milled down about 3/8 inch. Weiand claims it is to give better performance without going to a single plane intake, where the low rpm would suffer.
#7
Dr. Detroit
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Any dual plane intake benefits in flow from milling the divider out.......the ZL-1/L-88's were almost removed from the casting back then......for racing they were milled and the corresponding plenum area milled out larger.......the LT-2 454 test car was milled out and a dominator plate welded on it.
A 489 needs as much flow as it can get so I say mill it.......any 489 is going to make 600 ft/lbs. torque easily, and the swept volume far out ways the LS-6 manifolds ability to move air.
VortecPro made amazing power with this manifold but unsure if it was milled.
I say do it......with an engine that large.....the intake is a cork.
The only reason dual planes exist is for carb signal....they signal a carb better below 3000 rpm than a open plenum. Of course milling this negates the whole idea.......
A dual plane make more average power apples to apples strictly due to carb signal....that's it....that is how it works......it tricks the engine into think it is two four cylinders, it is actually ingenious how it works......
If you can make an 850HP and a Super Victor signal on a stock L-48.....you will make about the same average power and never know it was on there.......
Jebby
A 489 needs as much flow as it can get so I say mill it.......any 489 is going to make 600 ft/lbs. torque easily, and the swept volume far out ways the LS-6 manifolds ability to move air.
VortecPro made amazing power with this manifold but unsure if it was milled.
I say do it......with an engine that large.....the intake is a cork.
The only reason dual planes exist is for carb signal....they signal a carb better below 3000 rpm than a open plenum. Of course milling this negates the whole idea.......
A dual plane make more average power apples to apples strictly due to carb signal....that's it....that is how it works......it tricks the engine into think it is two four cylinders, it is actually ingenious how it works......
If you can make an 850HP and a Super Victor signal on a stock L-48.....you will make about the same average power and never know it was on there.......
Jebby
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pauldana (01-16-2019)
#8
Race Director
Any dual plane intake benefits in flow from milling the divider out.......the ZL-1/L-88's were almost removed from the casting back then......for racing they were milled and the corresponding plenum area milled out larger.......the LT-2 454 test car was milled out and a dominator plate welded on it.
A 489 needs as much flow as it can get so I say mill it.......any 489 is going to make 600 ft/lbs. torque easily, and the swept volume far out ways the LS-6 manifolds ability to move air.
VortecPro made amazing power with this manifold but unsure if it was milled.
I say do it......with an engine that large.....the intake is a cork.
The only reason dual planes exist is for carb signal....they signal a carb better below 3000 rpm than a open plenum. Of course milling this negates the whole idea.......
A dual plane make more average power apples to apples strictly due to carb signal....that's it....that is how it works......it tricks the engine into think it is two four cylinders, it is actually ingenious how it works......
If you can make an 850HP and a Super Victor signal on a stock L-48.....you will make about the same average power and never know it was on there.......
Jebby
A 489 needs as much flow as it can get so I say mill it.......any 489 is going to make 600 ft/lbs. torque easily, and the swept volume far out ways the LS-6 manifolds ability to move air.
VortecPro made amazing power with this manifold but unsure if it was milled.
I say do it......with an engine that large.....the intake is a cork.
The only reason dual planes exist is for carb signal....they signal a carb better below 3000 rpm than a open plenum. Of course milling this negates the whole idea.......
A dual plane make more average power apples to apples strictly due to carb signal....that's it....that is how it works......it tricks the engine into think it is two four cylinders, it is actually ingenious how it works......
If you can make an 850HP and a Super Victor signal on a stock L-48.....you will make about the same average power and never know it was on there.......
Jebby
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^THIS^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^
Someone finally gets it,,,
Someone finally gets it,,,
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Jebbysan (01-16-2019)
#9
Dr. Detroit
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I also want to add that putting one of those HVH "Super Sucker" carb spacers on a Dual Plane intake is a waste of $200. But on an open plenum intake....it can help signal the carb much better at certain points in the rev range.......
Also...if you stare at a dual plane intake and pay attention to the runner layout....you can roll through the Chevy firing order in your head, point to the runners and notice that they are orientated LOW/HIGH.....the higher runners come right after the lower runners and skip back and forth......this increases the amount of available vacuum at the booster by having the booster pulled by a predetermine set rather than from any of the eight pulling from one plenum.
Think of it like this:
L H L H L H L H
1 8 4 3 6 5 7 2
This splits the pulses in half.......
Jebby
Also...if you stare at a dual plane intake and pay attention to the runner layout....you can roll through the Chevy firing order in your head, point to the runners and notice that they are orientated LOW/HIGH.....the higher runners come right after the lower runners and skip back and forth......this increases the amount of available vacuum at the booster by having the booster pulled by a predetermine set rather than from any of the eight pulling from one plenum.
Think of it like this:
L H L H L H L H
1 8 4 3 6 5 7 2
This splits the pulses in half.......
Jebby
Last edited by Jebbysan; 01-16-2019 at 03:03 PM.
#10
Le Mans Master
Also...if you stare at a dual plane intake and pay attention to the runner layout....you can roll through the Chevy firing order in your head, point to the runners and notice that they are orientated LOW/HIGH.....the higher runners come right after the lower runners and skip back and forth......this increases the amount of available vacuum at the booster by having the booster pulled by a predetermine set rather than from any of the eight pulling from one plenum.
Think of it like this:
L H L H L H L H
1 8 4 3 6 5 7 2
This splits the pulses in half.......
Jebby
Think of it like this:
L H L H L H L H
1 8 4 3 6 5 7 2
This splits the pulses in half.......
Jebby
#11
Dr. Detroit
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Jebby
#12
Melting Slicks
Whether you have a 4-7 swap or not, the dual-plane manifold flow sequence is still L-H-L-H-L-H-L-H.
#13
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I'm not seeing the difference between the original firing order (with the 5-7 issue you mention), and having a revised firing order resulting in cylinders 4 & 2 pulling sequentially out of the same corner.
#14
Dr. Detroit
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They are in the Comp catalog if you want to check it out though.........
Jebby
Last edited by Jebbysan; 01-17-2019 at 07:56 AM.
#15
Dr. Detroit
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I don't think it makes a s&%t bit of difference, but as it was explained to me by Gordon Halloway at Comp......the vacuum pulses coming from that corner are one after the other and can create distribution problems at high RPM (6000+)....but to me it is rob Peter to pay Paul.....so a 4-7 as designed would have zero effect on a dual plane if I could tell you it worked at all.
Jebby
#20
Le Mans Master
That's exactly what we used to do , leave a 1/4" lip.back when we didn't have near as many intake choices nearly every one did it.