340 Six Pak...smokin', or blowin' smoke?

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Captainkirk

Captainkirk

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Which one....?
From what I've read, a good 4-barrel double-pumper will out-perform the 340 Six Pak setup on the dyno. You have to admit, though...there are few setups as visually exciting as 3 Holleys spooning on top of an aluminum manifold. Moreso, I believe, than a nice dual quad setup.
But the question at hand is...can the Six Pak setup be made to perform as well as a four barrel in a street-motor application? Does anyone have any dyno numbers or ET slips to offer in the way of confirmation? I'm sure the outboard vacuum carbs are fantastic in a typical 'goose-it-off-the-stoplights' scenario, but how about in an actual racing application? Or was this just a well-thought-out sales gimmick (like the Pontiac Tri-Power, with it's mechanical progressive linkage)?
Your opinions?
 
The 6 pack can perform toe to toe with a 4bbl. Carb within reason of it's application. First things first! The intake is a dual plane that lists its performance RPM band as 1500-6500. This is the same as the RPM.

Secondly, the 6 pack carbs are rated under the way they do 2bbl.'s and it is not the sMe as a 4bbl.! The 6 pack carbs converted to the 4bbl. rating method will equal (IIRC) 955 cfm's.
That is a large 4bbl. that might not work out so well on it's own as a double duty car or a street strip package. This is truly application, Combonation and tuner dependent issue.

This is where the 6 pack can be a better set up. Drivability! On the primary (center) carb. It is small. So there will be a lack of omph as compared to the larger side of a single 4bbl.
The. There's the opening of the out board carbs. Just like a 4bbl., but a bit more explosive since the 2 out board carbs open togther. There (2bbl. Rating of) 500 cfm each really opens up the flow path.

To have a set up that is mechanical rather than vacuum would be very nice. But until you know what the engine can handle and that really is how fast it can gobble up the out board carbs, well, it will or should feel a little soggy until the engine can use them.
You'll learn fast, no worries there.

The intake;

The 6 pack flows really well for such an old part. But the best ports vs. the worst ports leave the intake a bit behind a RPM or a action plus/stealth. This is where the simple 4bbl. Dual plane makes itself stand up and out a little bit more and better.

While the difference is small, you'll be hard pressed to see much on a dyno when all things are equal and running great. Dyno tests from magazines to TV shows to a few posted on the net have shown the 6 pack, IF well tuned will do as well as any 4bbl. out there.

The draw backs of the 6 pack are expense and tuning. More so that the carbs 3 separate and sandwiched togther making changing out jets on the front 2 carbs a pain in the backside and slow to perform.

You do a 6 pack because you want a 6 pack.

Those that ***** about them ether can not tune a carb or (knowingly or not) had a troubled carb. Just keep thinking it is a 4bbl. When you tune it. It's just double the secondary work.
 

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well i think the factory 6bbl setups on the chev 427 and 440/ 340 came out "just before" the holley / edelbrock etc stuff really started to take off in terms of big performance

other thing you gotta 'member is the factories had to meet smog regs. this means no big 4500 holleys from factory. frankly, i'm surprised the hemi made it as far as it did carburetion wise
 
Rumble is right on, only thing i can add is i went from a Holley strip dominator with a 750 race holley with annular boosters to a mopar 6 pack intake deep port matched with the old holley DC hustle stuff mechanical 6 pack that has progressive linkage. i lost nothing on the single 4 and i still have to tune the 6 pack. No bog off the line and these carbs have more like 1100 cfm, i do have a hi stall 4,400, they will work better with a hi stall auto than a 4 speed.
 

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Never thought about jetting changes...LOL! Looks like a total PITA. It's good to know (at least from your experience) the numbers are there, performance-wise. The jury is still out for me. Right now I would be looking at around $1800.00 for carbs and manifold (new), and that doesn't include linkage or air cleaner. That's a lot of bread for 'equal-to' performance of a single 4-barrel Holley.
So gotta ask myself...is 'Wow-Factor' worth that sort of money?
 
You can have an engine outperform another on the dyno, but that doesn't translate to a win at the strip. IMO, a good tuned six pack will out perform a single four barrel on the dyno, all other things being equal. What is the CFM of a six pack? 1200? Certainly on a well prepped engine, the six pack will have higher horse power numbers up top. But most six packs would lose out on the street to a well prepared single four barrel, IMO.
 
There an EFI version of the 6 pack. The member Dustpan has it installed on his duster.
 
And, before anyone mentions it, I've been cautioned before about buying 'used' as it appears that in most cases, amateur wanna-be's can't keep from screwing with these things and messing them all up.
 
To be honest, I don't see them being out performed. But that is also within the perameters of what the 6 pack was designed for. Many people push the limits of the design. Or AKA, it's intended useage/abilty.

I waited and waited a long time to purchase parts. Searched and searched. I found a place dumping there long shelved parts. I scored all brand new carbs for less than $700 to my door. Some places list the center carb for over $700.

I'm not a fan of rebuilding Holley's. My luck/skill level on them just sucks. I have MUCH better luck doing Carters. But I allways prefer a brand new carb. Less B.S.!

Bobby, the converted MoPar 6 pack rating to a 4bbl. is 955 cfm.
 
rumblefish360 said:
To be honest, I don't see them being out performed. But that is also within the perameters of what the 6 pack was designed for. Many people push the limits of the design. Or AKA, it's intended useage/abilty.

I waited and waited a long time to purchase parts. Searched and searched. I found a place dumping there long shelved parts. I scored all brand new carbs for less than $700 to my door. Some places list the center carb for over $700.

I'm not a fan of rebuilding Holley's. My luck/skill level on them just sucks. I have MUCH better luck doing Carters. But I allways prefer a brand new carb. Less B.S.!

Bobby, the converted MoPar 6 pack rating to a 4bbl. is 955 cfm.
Click to expand...

Right. I went back and saw where you said that. I am sure it's spot on. Still more than most four barrels. And you gotta love the shock factor.
 
What about 'hang time'? With no outboard pumps when you mash it you are standing the primary butterflies on end. I believe these had a 50cc pump in the center bowl, but is that enough for 'seat-of-the-pants' throttle response like a DP? I can sure tell the diff between a DP and a vac secondary Holley.
I realize those jumbo elephant diaphragms allow the outboards to ease in gradually, but I can't imagine there not being some 'felt' lag involved?
 
Don't they make throttle plates with angled idle adjustment screws now for the outboard carb? And metering blocks that make jet changes easier? I thought I saw somewhere it is available now.
 
Louie70Dart said:
Don't they make throttle plates with angled idle adjustment screws now for the outboard carb? And metering blocks that make jet changes easier? I thought I saw somewhere it is available now.
Click to expand...
Weber makes them for center hung bowls on the Holley 4 barrels. I would guess they might fit the center carb?
Thought the outboards used metering plates though.....
 
Ok thanks, I knew I had something worded wrong. But the metering plates make jet changes easier right? At least that's what I got out of it. Heres a video showing the lag to the outboards opening up. On a dyne, maybe that's one reason, I don't know. I trust your guys knowledge more than my ejimekated guess. LOL
[ame="https://www.youtube.com/watch?v=Eq7KEEMkUD4"]Sehr Performance Machine / Franks 340 6 Pack - YouTube[/ame]
6 pak tips. How good are they?
http://www.mopar1.us/6barreltips.html
Oh, sorry Captain, didn't mean to hijack. Hope you don't mind.
Darn it, I had the links to what I was talking about, I swear I didn't make it up!
 
Louie70Dart said:
Don't they make throttle plates with angled idle adjustment screws now for the outboard carb? And metering blocks that make jet changes easier? I thought I saw somewhere it is available now.
Click to expand...
Yes, Pro Max is one company that makes stuff for the 6 pack carbs.

Louie70Dart said:
Ok thanks, I knew I had something worded wrong. But the metering plates make jet changes easier right? At least that's what I got out of it. Heres a video showing the lag to the outboards opening up. On a dyne, maybe that's one reason, I don't know. I trust your guys knowledge more than my ejimekated guess. LOL
Sehr Performance Machine / Franks 340 6 Pack - YouTube
6 pak tips. How good are they?
http://www.mopar1.us/6barreltips.html
Oh, sorry Captain, didn't mean to hijack. Hope you don't mind.
Darn it, I had the links to what I was talking about, I swear I didn't make it up!
Click to expand...

Metering plates are not metering blocks. There two different things.
The plate itself meters the fuel. There not in increments where as the metering block has jets for a fine tune since jets go up in small amounts where the plates jump in changes vs. the jets.
 
Capt. asks about hang time? Is this the slow delay in the secondary opening your talking about? Looks exactly like every other vacuum secondary carb I have seen.
 
I have two six pack set ups on my 71 340 duster and 72 340 cuda. One 4 speed and one auto. They took a bit to tune but run great. They run great just cruising around and when you put it to the floor no bog. It does seem in the 4 speed car you can feel the outside carbs hit harder but that might be do to the engine build though

It does take time getting the idle circuits set and jetting etc but its worth it. I don't think it gave up any power.

Plus they have a look to them

10393868_10152526030301465_2393967720721013176_n_zps07c27ff4.jpg
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rumblefish360 said:
Capt. asks about hang time? Is this the slow delay in the secondary opening your talking about?
Click to expand...
Yes, that's exactly it. I realize it's a two-sided coin...'hang time' versus WFO bog when you stand a 4 barrel's mechanical butterflies on their tippy-toes. I'm assuming this can be 'tuned out' (compensated for) on outboard carbs much the same as it can be with vac sec carbs (i.e. Holley spring kits) or double pumpers (longer/larger secondary pump shot/stroke). Sorta wondering out loud if lighter diaphragm spring kits are available for the outboard carbs as the are for the VS Holleys......
 
Thanks... And good question about the springs. I don't know if they make the quick change style lid for 6 pack carbs. Everytime you have to take out the bolts and hope not to rip the diaphragm.

Don't remember what color spring is in my 4 speed set up but it had to be a bit stronger to stop the bog. Now from a dead stop you punch it takes off with zero hesitation. I do notice if you are at say 45mph and just punch it the car takes off hard. But if you try to like easily lay into the throttle it will stumble a bit and then they open(must be on the verge of jut enough vacuum to open them). Never bothered me because usually I am just cruising around and when you go to pass someone I grab the next lower gear and hold it for everything it has.

inside video of duster..was turning a 2.76 gear. Now a 3.55. I will have to get a wide open pull on video through the gears now. Motor still needs to be finished being broke in

[ame]https://www.youtube.com/watch?v=piGed6Dezb0&feature=youtu.be[/ame]
 
It looks like the diaphragm housing is similar. I wondered the same thing about changing springs. I found a few sites for tweaking the carbs, and adjustment tips. Haven't done so cause worried about hijacking.
 
Louie70Dart said:
It looks like the diaphragm housing is similar. I wondered the same thing about changing springs. I found a few sites for tweaking the carbs, and adjustment tips. Haven't done so cause worried about hijacking.
Click to expand...

Hijacking....? You mean this thread? Hell, no! Go right ahead and post whatever you want. This is a 'discussion' as are all my threads. I don't get all bent out of shape over petty stuff like that.
 
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