Upgrading my 340

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Raul

Raul

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Mukilteo/Marysville, WA
I have rebuilt my engine through a machine shop that upgraded my heads to aluminum with much bigger ports. I wish I knew what the specs meant. The car dyno's at 320 HP to the wheels. I have a 650 double pumper on it. I'm thinking of buying a complete aftermarket 6pak setup. I think from Herbs Automotive for $2800.00

My question is : Would it be better to invest in a good electronic fuel injection system instead? What kind of increased power may result in differences between the two systems?
 
6 packs are basically a fashion statement
Depending on the efi it mainly increases driveablity. Hard to beat the carb.
 
I will agree with the above except "Fashion statement" for a 6 pack.

The efi would be better on many fronts for drive ability and tuning chore(s) that will have to be done on the day you install it.

From a power point, the 6 pack is approx. equal to a 950 cfm 4 barrel carb. I'd bet the efi has more air flow capabilities. But the engine, on the other hand, will only consume as much as it needs. I doubt ether system is a short fall.

A bunch of whiners will allways complain about tuning a 6 pack. It is not an easy thing and down right hard if you have never had one much less ever tuned a carb. Against the efi, it is a nightmare by compare. Since the efi is plug in and go play. And that is huge and that is why it gets my vote based on what I read from you.
 
I just mean if looking for performance both are gonna cost a lot with little to no gain over the basic 4 bbl combo.

Every dyno shoot out ive seen with the 6 pack loses to airgap or similar intakes.
 
Don't waste your time with a 6 pack.

The real question is what's wrong with what you already have. I doubt I would have used a 650 just because the booster swallows bilge water but that can be addressed.
 
If you're weighing the option of spending $2800 to replace the 650DP you currently have for what little improvement in power a 6bbl or efi could possibly provide, you may want think heavily about only spending 1/8 of that on a 750DP instead, especially if you're strictly looking at it from a power stand point.
 
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I agree with Yellow Rose, what is wrong or what is your current combo. You should have received a build sheet with your motor, or call and ask for it. You may not get what your looking for with just a carb change.

Did your dyno run include an air fuel ratio print out? Was it a dyno tune or just a "here is what your getting" run?
 
My fashion statement as you say. Yes it's a factory original. Try to find one in today's market.

20160324_194532.jpg
 
273 said:
I just mean if looking for performance both are gonna cost a lot with little to no gain over the basic 4 bbl combo.
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I'm 100%. behind that! And in all honesty, the gain from a 650 to a 750 is probably only 10-15hp. And I say That without care to your combo because that is what often is seen.

Every dyno shoot out ive seen with the 6 pack loses to airgap or similar intakes.
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Not everyone I have seen.

But let's be real and honest about a 6pack. You build one because we you want to not because we you need to.

The old as a dinosaur intake holds its own against anything dual plane within its perimeters of operation. That intake is the way of way of gaining power.
Multi carb it!
 
I don't know F.I. seems the way to go if you buy the correct set-up..6 packs look all pretty but a properly tuned 850 will kick the piss out of it all day long:D:D
 
stroked340 said:
I don't know F.I. seems the way to go if you buy the correct set-up..6 packs look all pretty but a properly tuned 850 will kick the piss out of it all day long:D:D
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On a track condition, YES!
For the flexabilty that it was designed for, no way.
kris hines said:
Might be an interesting watch
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Bad comparo IMO because of the carb selection on "THAT SIX PACK IS NOT THE SAME AS IN THE MOPAR SIX PACK AND IS ACTUALLY LESS IN CFM."

Though I highly suggest a dual quad set up.
 
image.jpeg
Yes I love my six pack. Was it hard to dial in. Yes. Did it take me over a month. Yes. Did I have to drill out the outer carbs. Yes. Did I like the fashion statement. Yes. Was it hard to fit under the hood without scoop. Yes. Did I change the Vaccum springs. Yes. Did I re-jet center carb. Yes. Did I use mr. Norms air cleaner. Yes. WAS IT WORTH IT. HELL YES.
 
Fashion Statement??? You mean as in, an under the hood cosmetic upgrade look?? I'm looking for more pull and power. I know the engine's got more to give. I just need help in getting it out. Maybe it's my intake exhaust combination....
I have a pretty good Cam, (I think) My engine requires a vacuum pump in order for the power brakes to work. I know the stock 340's didn't require that, so i'm thinking the cam is fairly hefty. I wish I knew more of how to produce power without adding Nitrous or reverting back to opening up the engine to do upgrades. My car only does 13.58 in the quarter mile. I was hoping high 12's. Is that un realistic? I've read about having too big of a carb for the Cubic Inch displacement and horsepower would be frivolous and actually not be beneficial. I've seen the formula to calculate the size of carburetor required and a 650 is at the high end. I see a couple of you recommending a 750cfm. Wouldn't that just waste fuel and rob power? Or maybe with a different dual plane intake that provides better breathing and distribution of air fuel mixture the car would respond with more torque and acceleration power. What about my headers? what is the recommendation there. I bought a set for roughly $225.00 that I believe has 1 1/2" pipes attached to them. it took modification to fit them in but I had wished now that I invested more $$$ in hopes of better exhaust flow/performance. Aren't 6paks adding at least 15 horses? I think that was the difference in the stock motors anyways. Will a 750cfm add at least that much? When the car was dyno'ed it was in fact dyno tuned.They rejetted the carb andf it did include an airfuel ratio printout.
 
What does it MPH, that's tells a bigger story than ET.

The famous what's the smallest carb to run on my car formula! Absolute garbage when it comes to making power and having a car ET it's best.
 
The problem with carb rating it actually doesn't correspond to what your engine uses. It's more a measurement of restrictiveness. Say your 650 pulls 3" of vacuum at full throttle and a 750 pulls 1.5" both carbs would be pulling 750 cfm the rating doesn't matter cause it depends at what vacuum. You can check the amount of vacuum at a full throttle run and that will tell if yours is to small or not.
 
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Bullet point your questions. LMAO!
Raul said:
Fashion Statement??? You mean as in, an under the hood cosmetic upgrade look?? I'm looking for more pull and power. I know the engine's got more to give. I just need help in getting it out. Maybe it's my intake exhaust combination....
I have a pretty good Cam, (I think) My engine requires a vacuum pump in order for the power brakes to work. I know the stock 340's didn't require that, so i'm thinking the cam is fairly hefty. I wish I knew more of how to produce power without adding Nitrous or reverting back to opening up the engine to do upgrades. My car only does 13.58 in the quarter mile. I was hoping high 12's. Is that un realistic? I've read about having too big of a carb for the Cubic Inch displacement and horsepower would be frivolous and actually not be beneficial. I've seen the formula to calculate the size of carburetor required and a 650 is at the high end. I see a couple of you recommending a 750cfm. Wouldn't that just waste fuel and rob power? Or maybe with a different dual plane intake that provides better breathing and distribution of air fuel mixture the car would respond with more torque and acceleration power. What about my headers? what is the recommendation there. I bought a set for roughly $225.00 that I believe has 1 1/2" pipes attached to them. it took modification to fit them in but I had wished now that I invested more $$$ in hopes of better exhaust flow/performance. Aren't 6paks adding at least 15 horses? I think that was the difference in the stock motors anyways. Will a 750cfm add at least that much? When the car was dyno'ed it was in fact dyno tuned.They rejetted the carb andf it did include an airfuel ratio printout.
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Dismiss the carb size notion and fuel gobbling ides.
Header sor we should be 1-3/4. Use tti headers and there 2-1/2 exhaust.

Adding a six pack doesn't add 15hp. Only vs the small carb the 340 came with. Once you go away from stock, it becomes a new ball game. And tuning what ever is on top of the intake is key.

Running 12's with s not unrealistic but reasonable except we don't know what is in your engine or what trans, stall, rear gears or tire size size is. How is the chassis set up.
 
273 said:
The problem with carb rating it actually doesn't correspond to what your engine uses. It's more a measurement of restrictiveness. Say your 650 pulls 3" of vacuum at full throttle and a 750 pulls 1.5" both carbs would be pulling 750 cfm the rating doesn't matter cause it depends at what vacuum. You can check the amount of vacuum at a full throttle run and that will tell if yours is to small or not.
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Care to prove that?
A 650 pulling 750 at a certain rpm just like a 750 pulls 750 at that rpm?

Never heard of a carb to be seen as a restriction in the manor you worded it.
 
rumblefish360 said:
Care to prove that?
A 650 pulling 750 at a certain rpm just like a 750 pulls 750 at that rpm?

Never heard of a carb to be seen as a restriction in the manor you worded it.
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As you probably know 4 bbls are rated at 1.5" of vacuum. So if you bolt a 750 cfm carb on your engine and at full throttle it's pulling 1.5" of vacuum then it's pulling it's rated 750 cfms through your engine. But more than likely it's gonna have a different vacuum value. So say at 1" of vacuum it probably be around 650 cfm and at 2" of vacuum be around 850 cfm.

The OP just has to measure the vacuum on a full throttle run to see if the carb is to restrictive.
 
What about the rest of the cars specs? Rear gears? Stall speed? Trans? Suspension? Etc..
 
You have some sorting out to do..... Buy all the Fuel Management you want but don't count on the car meeting your new expectations. When you say the motor doesn't build enough vacuum for the PB indicates something ain't adding up based on the RWH on the dyno.

Stick a vacuum gauge on it and report back... Oh yeah, as stated what about the rest of the car setup wise?

JW
 
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