Intake swap thought

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L31MaxExpress

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I’m wondering why you didn’t go with a single plane efi intake. I got a spectre 90 to 4” adapter for my bbc and ported,plugged and filled the stock aluminum bottom for now with vortec ported bowtie heads. I’ve been waiting a year for fast to release their crank trigger and I have used a MSD dual sync distributor as there is an interface with the cap and wires. I’m hoping for close to 400/400 for hp and torque. I plan on using the stock a/c ps pump bracket and it appears that it will need trimming for the tall valve covers has anyone else done this?

Torque is why I did not go with a single plane. This engine has had a dual plane efi intake on it though.
 

Pro439

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Torque is why I did not go with a single plane. This engine has had a dual plane efi intake on it though.
All the reading I’ve done has said a dual plain doesn’t work as your not trying to an air/fuel mixture sustained
 

L31MaxExpress

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All the reading I’ve done has said a dual plain doesn’t work as your not trying to an air/fuel mixture sustained
Whoever told you that does not have a clue! Its nothing to do with air/fuel. It has to do with intake resonance and combined runner length. A dual plane has much longer runners for intake wave tuning which creates higher VE and more torque at the RPM they are tuned to operate in. Basically from idle to 6,500 on a performer rpm. The marine dual plane made a stupid amount of torque from 1,500-5,500 and did not fall off hp wise until 6,200 rpm with the 232/244 @ 0.050 Lunati Bootlegger cam I was running at the time.
 

Pro439

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Whoever told you that does not have a clue! Its nothing to do with air/fuel. It has to do with intake resonance and combined runner length. A dual plane has much longer runners for intake wave tuning which creates higher VE and more torque at the RPM they are tuned to operate in. Basically from idle to 6,500 on a performer rpm. The marine dual plane made a stupid amount of torque from 1,500-5,500 and did not fall off hp wise until 6,200 rpm with the 232/244 @ 0.050 Lunati Bootlegger cam I was running at the time.
In a fuel injected setup your not trying to keep the air fuel mixed you only have the air portion the fuel is put in after the intake which is why you only see single plane intakes and no dual plane intakes. Unless you have a tbi then it would matter. If the injectors are located at the end of the intake runner it would rather have a short runner versus the dual plane and the tests that I’ve seen done as far as polished versus non polished runners is almost nill porting on the other hand you can gain quite a bit but again you need to know what your doing and where you want to run the engine and the runner length has to do with the tuning of a carburetor of which you mentioned but doesn’t correlate with fuel injection. I personally have never liked the ramjet as the cylinders at the front get a better air supply than the cylinders in rear of that intake
 
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L31MaxExpress

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In a fuel injected setup your not trying to keep the air fuel mixed you only have the air portion the fuel is put in after the intake which is why you only see single plane intakes and no dual plane intakes. Unless you have a tbi then it would matter. If the injectors are located at the end of the intake runner it would rather have a short runner versus the dual plane and the tests that I’ve seen done as far as polished versus non polished runners is almost nill porting on the other hand you can gain quite a bit but again you need to know what your doing and where you want to run the engine and the runner length has to do with the tuning of a carburetor of which you mentioned but doesn’t correlate with fuel injection. I personally have never liked the ramjet as the cylinders at the front get a better air supply than the cylinders in rear of that intake
You can think what you want. There are dual plane MPI intakes. The dual planes build more torque. Has nothing to do with air/fuel mixing. It has to do with resonance wave tuning and runner length. The long divided runners have stronger resonance waves. The resonance waves help volumetric efficiency. Engines that need good low-midrange torque were sometimes fitted with dual plane manifolds. I have run one and I have run other port fuel injected intakes. The dual plane adds 30-40 ft/lbs at lower rpm compared to a single plane at low rpm. It matters and I have tested it. A dual plane port fuel injected intake makes more low-speed torque than GM TPI but less midrange. The dual plane will also make alot more power at higher engine speeds than TPI.

The only reason you do not see more dual plane MPI intakes is because the manufactures like Holley and Edelbrock falsely believe everyone needs a race looking manifold and they are easier to get injection bungs and fuel rails into with all the ports being the same height and dimensions.

The LT1 is a perfect example of what happens when the runner length is short.

Look at any of Holdeners tests on runner length and tell me that runner length on a port fuel injected setup does not matter because it certainly does.
 

L31MaxExpress

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Here is a totally extreme example of runner length with port fuel injection. A dual plane has longer runners than a single plane and by design it actually has multiple intake resonance points. The dual plane makes more torque than the single plane.

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A dual plane port fuel injected intake makes more low-speed torque than GM TPI but less midrange. The dual plane will also make alot more power at higher engine speeds than TPI.
That's interesting, most of the data I have seen shows TPI beating everything below 3000rpm but the dual planes were probably carburetor applications in those tests (which you think would be better due to charge cooling?). Just to be pedantic, when you're talking low-speed, is that below 2500rpm and midrange would be like 2600-3800rpm?
 

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That's interesting, most of the data I have seen shows TPI beating everything below 3000rpm but the dual planes were probably carburetor applications in those tests (which you think would be better due to charge cooling?). Just to be pedantic, when you're talking low-speed, is that below 2500rpm and midrange would be like 2600-3800rpm?
I tested TBI vs TPI many moons ago. TPI did not beat a TBI dual plane until about 2,600 rpm and only made more torque in a narrow rpm window between 2,600 and 3,800 ish. At 1,500-2,000 rpm, TPI is very soggy on torque which is right where these trucks cruise in overdrive. The TPI only makes good resonance waves around ~3,200. There is a different order wave (might be 3rd or 4th wave, I forget which) that comes on around 6,400 but you would never get to that one on most TPI setups. You see that wave starting to boost VE and power on almost every ~6,000 rpm TPI dyno test. Right at the end of the testing the torque and hp curve starts to spike upwards.

Down at 1,000-2,500 rpm a PFI dual plane will make more torque than a TPI even without the effect of charge cooling.
 
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Pro439

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I tested TBI vs TPI many moons ago. TPI did not beat a TBI dual plane until about 2,600 rpm and only made more torque in a narrow rpm window between 2,600 and 3,800 ish. At 1,500-2,000 rpm, TPI is very soggy on torque which is right where these trucks cruise in overdrive. The TPI only makes good resonance waves around ~3,200. There is a different order wave (might be 3rd or 4th wave, I forget which) that comes on around 6,400 but you would never get to that one on most TPI setups. You see that wave starting to boost VE and power on almost every ~6,000 rpm TPI dyno test. Right at the end of the testing the torque and hp curve starts to spike upwards.

Down at 1,000-2,500 rpm a PFI dual plane will make more torque than a TPI even without the effect of charge cooling.
The problem with what you have from Holley is a the same as a single plane intake only with stack runners. Unless you’re class racing and restricted to what manifold you can use it doesn’t make much sense to get a dual plane with the bungs fitted correctly in the ports versus off the shelf cost of a single plane. I do agree however that for a small roller cam engine of which not a lot of people build but I did and used a stock L31 intake which is just a big open plenum with roughly the same length runner a single plane would have. The gains you get aren’t that huge to offset the cost difference. I asked a couple of places that do custom work and they were between $900 and $1500 to modify a carburetorated intake with fuel injector bungs unless you have a secret that can’t be found on the internet. I would have gone with a dual plane on my 383 build but the cost of the modified intake alone removed it from the equation. I think they should have a street single plane intake but I don’t believe the demand is high enough for them to make it. Luckily on the big block side they have the peanut port single plane. I’ve never actually seen anyone do a small roller cam comparison between a dual plane and a single plane EFI setup to say yeah absolutely this is worth the little extra torque in that RPM range to do it like that. I also am not saying that using a stock spider injection setup is the way to go either it’s just what I did with porting and filling and welding work done to. I haven’t been able to run it yet as I am still waiting for the crack trigger from fast for it as I went with a double roller timing chain and am using a factory gm computer reprogrammed. I am using a small crower hydraulic roller with a small port bowtie head 10 to 1 compression should run pretty good but anything will feel like a rocket after the over 250,000 mile wore out 350 with piston knock
 

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The problem with what you have from Holley is a the same as a single plane intake only with stack runners. Unless you’re class racing and restricted to what manifold you can use it doesn’t make much sense to get a dual plane with the bungs fitted correctly in the ports versus off the shelf cost of a single plane. I do agree however that for a small roller cam engine of which not a lot of people build but I did and used a stock L31 intake which is just a big open plenum with roughly the same length runner a single plane would have. The gains you get aren’t that huge to offset the cost difference. I asked a couple of places that do custom work and they were between $900 and $1500 to modify a carburetorated intake with fuel injector bungs unless you have a secret that can’t be found on the internet. I would have gone with a dual plane on my 383 build but the cost of the modified intake alone removed it from the equation. I think they should have a street single plane intake but I don’t believe the demand is high enough for them to make it. Luckily on the big block side they have the peanut port single plane. I’ve never actually seen anyone do a small roller cam comparison between a dual plane and a single plane EFI setup to say yeah absolutely this is worth the little extra torque in that RPM range to do it like that. I also am not saying that using a stock spider injection setup is the way to go either it’s just what I did with porting and filling and welding work done to. I haven’t been able to run it yet as I am still waiting for the crack trigger from fast for it as I went with a double roller timing chain and am using a factory gm computer reprogrammed. I am using a small crower hydraulic roller with a small port bowtie head 10 to 1 compression should run pretty good but anything will feel like a rocket after the over 250,000 mile wore out 350 with piston knock

I have seen the dyno test on a LS between the Holley dual plane 2x4 manifold and Edelbrock Victor single 4 single plane. HUGE difference in torque and the same HP. I do not see why a single 4 barrel dual plane would make much if any less. I saw the same kind of low-speed gain running the single 4bbl dual plane L31 Marine intake.

It is a bigger difference than you are making it out to be. Dual plane is going to make considerably more torque than a single plane even with fuel being added at the end of the runners. The manifold manufacturers need to create proper manifolds for 95% of the vehicles on the road. Single plane intakes suck on the street in heavy vehicles with tight converters and tall gearing.

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