Six Pack and Vacuum

[erik70rt]

How much vacuum is needed to run a typical six pack setup?  Can they be cammed up without too much difficulty?

[Cuda Cody]

If I recall, you're okay with anything over about 12 at idle, but I would want a bit more.  I think 14 to 16 would be the minimum I would want to run. 

Running a huge cam will also mess with the power brakes, if you have them.

[Chryco Psycho]

The original cams were designed with 115* LSA so while they make good power they retain vacuum at idle , most aftermarket cams are 112* at best making the idle calibration more difficult , it still can be made to work a the Holley carbs are more adjustable , but on some engines I have had to insert a wire in the idle bleeds to clean up the idle

[erik70rt]

Thanks. I'm beginning to rethink the six pack.  Seems like there's a lot more flexibility with a 4 bbl setup.  I loved the cam I had in the barracuda and that only had about 5lbs of vacuum.

[Chryco Psycho]

I have tested both , a Mopar M1 or eddy RPM with a Proform carb will kill a 6 pack & is far more adjustable , the 6 pack is for looks

[erik70rt]

Is the M1 a single or dual plane?  I have a Mopar manifold in the garage that I think is a single plane.  I'll have to pull it off the shelf and check. 

[Chryco Psycho]

M1 was Mopars name for all of their intakes but the one I am talking about is the M1 single plane , kick ass intake 

[js27]

Everybody I knew back in the 70's who owned a 340 or 440 six pack drove it for about 1 month and then the 6 pack went in the trash. They would get them running good for a day or two then back into them.Multi carbs-Multi problems...
JS27

[Chryco Psycho]

I disagree , once a 6 pack is properly set up it will stay set up .
The problem is modifications , you go from a factory 115* LSA cam to 110 & the vacuum signal changes , you cannot change the air bleeds & the problems start , this is why I like the Proform carbs , the air bleeds can be tuned to work with other modifications .
I have worked a number of tricks to make 6 packs work better on modified engines but the new single 4 bbl still works better .

[Fastmark]

I disagree , once a 6 pack is properly set up it will stay set up .
The problem is modifications , you go from a factory 115* LSA cam to 110 & the vacuum signal changes , you cannot change the air bleeds & the problems start , this is why I like the Proform carbs , the air bleeds can be tuned to work with other modifications .
I have worked a number of tricks to make 6 packs work better on modified engines but the new single 4 bbl still works better .

I agree completely. When the vacuum signal changes it screws up the idle and you have problems. I removed the air idle bleeds on my six pack and put in small brass Allen heads screws and fix the idle. I've never had problems with it staying tuned until I changed my cam. I need to start over. It changed my vacuum again.

[screamindriver]

I have a comp cams extreme energy cam in my 440-6...Single digit vacuum at idle, promax metering block and plates, and a vacuum reserve canister fastened  under the fender on the driver's side to the inner fender/firewall support bracket...I have enough vacuum to run power disc brakes and AC... Absolutely flawless performance it'll roast the tires from take-off to 55mph easily with an auto-4.10 dana drivetrain...A 6bbl can be tuned you just need to spend some time to get it right..As stated after the initial set-up I haven't touched it in years other than gaskets,needles and seats etc... The usual stuff that gives it up over time..