Done with six pack

[Ghoste]

Thanks Troy, I should have left the word "tuning" out of the search.

Oh, and excellent post Tom.

[charger1972]

A properly tuned six pak car will outrun it's  4bbl equal and not have problem after problem. I have run then for 35 years. Six paks have a bad reputation because people get frustrated with them.  They are stone reliable!

There is comprehensive guide  to set up and tune a six pak that has been posted here and on moparts too many times now. Over the years I compiled many peoples information into it and i have a lot of time invested in getting it to read right. There is at least one minor error about the pwr valve selection in it that the brainiacs on moparts have pointed out to me, but at this point i am not taking the time to copy edit any further as people would rather nit pik on the web boards than be helpful.   This is the reward for being nice and gracious to those who need technical support.

So i will leave you with this note as i am sure some one who lives here can post up the guide.
Rather than further blacken the stellar reputation of the six pak, I suggest you try tuning it properly and enjoy it.
No 4bbl set up will make the car run any better.  Be careful with the advice given here by others less informed

I love my sixpack,the reactions when i pop the hood,when a kid stares at the 440 sixpack badges on the hood,the noise they make when they open up.But i have read the tuning posts and tweaked them over and over,re jetted them and so on.It runs great, just doesn't perform like i think it should.I'm a mopar or no car kinda guy,and will never say anything bad about that set up and I'm not done with it,just putting it on hold for now.

[Ghoste]

Still, it seems strange that if you had it set up to kill that just switching to a stock Holley (and I'm only assuming the 3310 was not dialed in) that it was like "night and day".   Not that I don't think you'll extract greater performance from a well adjusted Proform, it just seems like there is something else wrong with that Six Pack.

[charger1972]

I totally agree with that.But i will have fun with a new set up and over the winter maybe screw around with the sixpack carbs some more.I don't plan on selling it,even though that would cover the cost of a new carb.

[Cooter]

What was it Ron said a few threads back???


Something along these lines..."There's NO WAY IN HELL a stock (IE 440 SIX PACK, even with it's SLIGHTLY larger cam), will EVER need 950 CFM and actually use it."


Why would a "Stock" 440 need 1350 CFM? Too much carb., too little motor IMO. Yes, they perform "ok" when tuned properly, but then again so does a 750 Holley on a Victor intake.

[Ghoste]

With vacuum secondaries it shouldn't draw more than it needs when properly set up anyway should it?

[BSB67]

The 6 pack is truly the best balance for street cars up to about 550 hp, and will still work well above that. The small 2 bbl/dual plane intake drives nicely and the WOT and the 950 cfm gives up little to nothing to the single plane 750 or 850 4bbl.  You simply cannot discuss quality of induction system and carbs, or carb size, without including the intake manifold.

[Ghoste]

Thats kind of where I thought its advantage was, less about airflow and more about distribution.

[FLG]

Heres my question,

2 identical cars, both 440's with the same specs. One setup with a factory 6 pack perfectly tuned, one setup with a proform or similar dp'er and a good flowing manifold but something not far from stock looking...CH4B for example, or one of the better flowing stock mopar intakes from a 71 440.

1/4 mile and dyno wise, which car would make more hp and be faster, and by how much? Taking all other variables out of the equation (driver error, wheelspin...etc)

[BSB67]

Heres my question,

2 identical cars, both 440's with the same specs. One setup with a factory 6 pack perfectly tuned, one setup with a proform or similar dp'er and a good flowing manifold but something not far from stock looking...CH4B for example, or one of the better flowing stock mopar intakes from a 71 440.

1/4 mile and dyno wise, which car would make more hp and be faster, and by how much? Taking all other variables out of the equation (driver error, wheelspin...etc)

Lets pretend they 60 ft the same...okay?

On a slightly modified 440 (400-425 hp ish) The 6 pack would have 1 mph ( i.e. .1 sec quicker) and about 5 more hp verses the CH4B with a good carb.  Add a 1" open spacer or mill the divider down for the CH4B and it would probably be a wash.  The gap will get wider as the hp goes up.

Verses a cast iron intake with a large Holley, 2 mph and .2 sec.  Peak power is still only 10 hp lower.  But the average power for the 4 bbl is down more because the iron manifold power drops like a stone at 5200 rpm where the 6 pack continues to pull decent power well past peak power and allows higher shift rpm, and a greater area under the hp curve (average power from 3600 to 6000 rpm).  The power gap gets bigger faster as hp goes up.

I have conducted a lot of track testing with several cars in this power range with different induction systems and is the basis for my opinion.

[FLG]

Thanks for the info 

Based on that, besides a numbers matching resto or just for looks.....i personally would than just throw on a nice Aluminum manifold and a dp'er and call it a day.

[oldschool]

What was it Ron said a few threads back???


Something along these lines..."There's NO WAY IN HELL a stock (IE 440 SIX PACK, even with it's SLIGHTLY larger cam), will EVER need 950 CFM and actually use it."


Why would a "Stock" 440 need 1350 CFM? Too much carb., too little motor IMO. Yes, they perform "ok" when tuned properly, but then again so does a 750 Holley on a Victor intake.

Why would a "Stock" 440 need 1350 CFM?

the six pack is not really 1350 cfm, as compared to the way they rate a four barrel. they rate 2 barrel carbs differenty.

[BSB67]

Thanks for the info 

Based on that, besides a numbers matching resto or just for looks.....i personally would than just throw on a nice Aluminum manifold and a dp'er and call it a day.

Right.  From a cost perspective it does not make a lot of sense.  It does take time to understand the 6 bbl and get it sorted out, they are harder to work on, fuel line access is a pain, need to remove carbs to access jets and more.  Every time I would tear into the carbs at the track, I would wonder if everything would get back together trouble free.

But to add to my previous post, when I put my 6 pack on my 508 cu in motor, it was only 10 lower in average power from a SD, with open spacer, and 950 4150 carb, without turning a screw, and made more power under 4500 rpm.  Again, the versatility of the 6 pack from 350 hp to 550 hp is phenomenal.

[Ghoste]

Very informative, thanks.   You don't have the six barrel setup on there now though, do you?

[BSB67]

Very informative, thanks.   You don't have the six barrel setup on there now though, do you?

No. 
440-2D with the 950.  It runs about even with the SD and 4 hole open spacer.  SD with a little more peak, but same average.

[ACUDANUT]

Six Pack and twin four set ups are like Trophy wives...The tend to impress, but require high maintenance.

I agree 100 percent.

[Cooter]

Why would a "Stock" 440 need 1350 CFM?

the six pack is not really 1350 cfm, as compared to the way they rate a four barrel. they rate 2 barrel carbs differenty.

According to the factory rated Carb CFM, it's 1350 with all three 2BBLs added together at WOT....Maybe the factory make a BooBoo?

[Ghoste]

I thought the way they were measured was different than the four barrel?  The factory was using the highest number available for marketing why would they rate them measured at the same vacuum as the four barrel if it gave a lower cfm?

[Cooter]

Don't make no nevermind no how, as if a "Stock" 440 only uses around 650 CFM, then it don't matter if they's "Only" around 900 CFM in a Six Pack, it's still too damn much.

[Ghoste]

No, but that wasn't your question.  Although I will ask this again, would it ever see that 950 capability interfere with vacuum secondaries?  The center one was "rated" at 500 so it would be used almost always, no?  The outer two would only come in as an "on demand" feature and shouldn't be doing anymore than improving fuel/air flow balance across the engine?  Yes, there are better carb intake systems for sure but as far as a stock setup which improves performance and gained a big marketing plus in 1969, it's a pretty sweet way to go I think.
Isn't that why so many Six Pack cars became ultra dogs on the street when backyard carb scientists altered them to either tip the outers in sooner or worse yet, make them mechanical?

[c00nhunterjoe]

Ah yet another "how much cfm is too much" debate..... I don't see how 950 cfm iss too much for a mildy modified 440 (cam,intake,exhaust) when there are plenty of articles with dyno tests on the 383 that showed an 850 dp made the best combo on a mild 383, yet you guys are saying a 650 or 750 is the max you will need on a 440.  Granted a lot of factors decide how much carb you need and if you are running a bone stock,8:1 engine through an iron intake then no, you don't need a big carb, but if you have a little compression, decent flowing heads, an intake matched to you cam\head\comp combo, then I can't see how a 950 is too big on a modified 440 when every dyno sheet comparison has showed otherwise.

[BSB67]

I purposely stayed away from this last time.  But I'll give it a shot.

It seems that everyone talks about "cfm" as some ultimate measurement, where in reality, it is a number that has no meaning by itself.  For a 4 bbl, it is actually XXX cfm @ 1.5" hg.  So a carb can, and will flow more or less than the advertised number depending on.....wait for it.....the pressure drop.  Guess what, our type of engines (street/drag) usually do not pull 1.5" hg at WOT.  At WOT, the carb will create a pressure drop across the venturi, which in effect restricts air flow (but provides the necessary pressure drop to meter the fuel - can't have your cake and eat it to).  It is absolutely incorrect to say that an engine only wants XXX cfm.  What is accurate to say is that an engine will only TAKE xxx cfm @ x.x" hg.  This part is important....if you reduce the pressure drop, the engine will TAKE more cfm.  Of course there is the point of diminishing returns...i.e. the carb is too big.

So let me give an example:  We run an engine on a dyno and it makes 550 hp.  The carb is a 950.  The dyno instrument tells us that the engine actually had an air flow of 800 cfm during the pull.  Wow.  I guess the motor only wants 800 cfm.  So we put a 800 cfm carb on and do another dyno pull.  Hmmm.... it only made 535 hp, and now the air flow is only 725 cfm.  This happens because the engine is pulling less than 1.5" hg.  So for the first pull the engine was pulling 1.1" hg, and on the second pull, the engine was pulling 1.25" hg, caused by the more restrictive smaller carb.  Of course the engine made less power because it pulled less air.

2 BBl carbs are rated at 3" hg.  So to compare them to a 4bbl you need to convert the 2 bbl rate cfm to 1.5" hg.  In the case of the 1350 cfm @ 3" hg 6BBL, the flow rate at 1.5" hg is actually 955 cfm (i.e. measuring it like a 4 bbl.).

[Ghoste]

In other words, advertised cfm is much like advertised duration with cam specs.

[BSB67]

In other words, advertised cfm is much like advertised duration with cam specs.

Actually, it is like every flow situation....they are always defined as" certain flow at a certain pressure", same as oil pumps, fuel pumps...etc..

[Ghoste]

Acually I meant more the validity of just comparing numbers across the board and assuming that all things were equal.  What you said but just the comparing part.