Six pack response...

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MAPS

MAPS

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As usual, I've come to the experts, always someone being able to help me with my stupid questions or needs.
Can someone tell me what is the "norm" of a response to a six pack smashed to the floor at around 2-2500 rpms ?
Is there a hesitation before the vacuum kicks in the end carbs or is it supposed to feel like the Dead Sea opened up and swallowed you....
Thanks in advance to any and all replies.
 
I don't know how relevant this may be to your question, but years back Chrysler Power magazine there was an article on tuning six pack secondaries by changing the vacuum bleed size on the secondary vacuum actuators to control the opening rates. The factory carb bleed orifice size differed according to the application, this article showed drilling and tapping the orifices for socket head machine set screws and drilling the set screws for custom orifice size. The general idea was to open the secondaries as quickly as possible without making the engine bog under load.
 
I would recommend replacing the diaphragms if they are old, they get stiff and don't open properly, you will notice the difference when they are new. then you can start tuning the vacuum circuit if you want.
 
Garrett Ellison said:
I don't know how relevant this may be to your question, but years back Chrysler Power magazine there was an article on tuning six pack secondaries by changing the vacuum bleed size on the secondary vacuum actuators to control the opening rates. The factory carb bleed orifice size differed according to the application, this article showed drilling and tapping the orifices for socket head machine set screws and drilling the set screws for custom orifice size. The general idea was to open the secondaries as quickly as possible without making the engine bog under load.
Click to expand...

Yes, thanks about that, I'm aware of the spring changes in the secondaries as well changing jets, even making the end carbs open manually instead of waiting for the vacuum to kick in. What I want to know is on a stock set up, more or less, how does it react. Is there that small hesitation ? When kicked at around 3k rpms do you feel the difference or does it just load and go as if it's any other carb set up at full throttle.

Now the reason I ask is I used to have a 440 6bbl car that was an original factory car and I'm not sure if it's the norm that it felt line it did, torque, B.B. etc. Compared to this small block I have now that doesn't have that torque that the 6 pack feels like a regular high performance 4 bbl carb .
I recall the original 6 pack, was " " heard, when it opened up. I can't say the same with the small block.
At times I feel like I may just go back to a 4 bbl set up and be done with the constant tuning of these 6 packs.
Dean thing does look nice, the jewel of any engine I've ever seen... Minus the elephant, but sometimes looks are not everything... I know, I see myself everyday when shaving and think, what does the missus see in me.Lol
Ok thank you.
 
brian6pac said:
I would recommend replacing the diaphragms if they are old, they get stiff and don't open properly, you will notice the difference when they are new. then you can start tuning the vacuum circuit if you want.
Click to expand...
I had the six pack rebuilt last summer but now that I'm thinking about itxi don't know is those were changed.. I'm going to look into that as well.
I know that you are well versed with these carbs, (i've pm'ed you about nitrous if you recall) so I want to ask you also if and when the diaphgrams are replaced do you have any suggestions about spring color swaps, etc for stiffness ?
Thanks.
MAPS
 
Tried to pm you but seems to be a problem, I will try tomorrow or see if you can send me a pm.
Brian
 
A factory stock vacuum six-pack will not give you a jerk and kick so to speak as the outer carbs open. It should be a smooth transition. This is also true of many 4 bbles. It is only after us rodders start jacking around with the QJ and TQ air valves, and the springs and things in the Holleys that a giant kick starts happening. Sometimes this results in a bog, and the kick is actually a delay that in the long run can slow things down

A good runnin factory sixpack had boatloads of torque and came on in a very predictable way. I had a 69 383 RR when I bought the 6bbl from a friend, and I thought the 383 ran fair. But that 6bbl made the 383 look like it was just parked. In their day, they were an awesome car.

Having said that, I'd love to strap on a 6bbl again for a little ride before I die

My old rig "back then" This faded old photo was taken in either 73 or 74, and by then had a 340 swapped in. You can't see the hood because of fading, but it had the black stripes and air grabber. 4 speed, Dana, trak pak, and aftermarket hang on a/c. Most of the time I owned it, it actually didn't have a 6bbl, but rather various Holley double pumpers and headers.

81sruds.jpg


Me in about 71--72, I was about 24

attachment-jpg.jpg
 
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you used to be able to get "strip kits" for them, that had a set of diaphragm springs, so you could tune the tip in point for the outboards. made a noticeable difference on mine
 
MAPS said:
As usual, I've come to the experts, always someone being able to help me with my stupid questions or needs.
Can someone tell me what is the "norm" of a response to a six pack smashed to the floor at around 2-2500 rpms ?
Is there a hesitation before the vacuum kicks in the end carbs or is it supposed to feel like the Dead Sea opened up and swallowed you....
Thanks in advance to any and all replies.
Click to expand...

Never owned one, but borrowed one from a friend when my new ford pick up laid down on me under warranty . 1969 charger , ran great and had great response / best I can remember , I waxed a new trans am fire turd taking her home with it !
Made him look stupid !
 
MAPS said:
As usual, I've come to the experts, always someone being able to help me with my stupid questions or needs.
Can someone tell me what is the "norm" of a response to a six pack smashed to the floor at around 2-2500 rpms ?
Is there a hesitation before the vacuum kicks in the end carbs or is it supposed to feel like the Dead Sea opened up and swallowed you....
Thanks in advance to any and all replies.
Click to expand...
Here's a Nicks Garage video of a 340 6 pack on the dyno. You will be able to see the outboard carbs open under full throttle acceleration. (starting at about 9:45 but you might find some tuning tips before that)
 
It is a complicated circuit that must be fine tuned in order to minimize the bog associated with opening the outboard carbs through the vacuum circuit. Fist of all, the center carb is known to slightly warp around the float bowl fastening screws due to a thinner design. When that happens, it can allow fuel into the vacuum chamber, which directly affects the outboard carbs. No or low vacuum delays the outboard carbs from drawing in the air/fuel mixture, delaying the application of that additional fuel, causing the bog. A complete rebuild of the carbs would require filing the mating surfaces flat on the center carb metering plate and the throttle body housing where they meet. The compensate for this, there used to be an aftermarket fix for the outboard carbs where you drill and fit accelerator pumps to eliminate the reliance on vacuum to draw in the fuel.

Tuning a six pak setup is a labor of frustration unless all of the components are in top shape, including wires, plugs, distributor, coil, and fuel distribution. Some old schoolers can whiz right through it, most people (including myself) can not. I’m learning tho, and am in the middle of rebuilding my entire setup. Currently waiting on the diaphragm rebuild kits to arrive, which are not included in any kit.

45D4881D-5F01-4848-BE1A-068C838F7F01.jpeg
 
cosgig said:
It is a complicated circuit that must be fine tuned in order to minimize the bog associated with opening the outboard carbs through the vacuum circuit. Fist of all, the center carb is known to slightly warp around the float bowl fastening screws due to a thinner design. When that happens, it can allow fuel into the vacuum chamber, which directly affects the outboard carbs. No or low vacuum delays the outboard carbs from drawing in the air/fuel mixture, delaying the application of that additional fuel, causing the bog. A complete rebuild of the carbs would require filing the mating surfaces flat on the center carb metering plate and the throttle body housing where they meet. The compensate for this, there used to be an aftermarket fix for the outboard carbs where you drill and fit accelerator pumps to eliminate the reliance on vacuum to draw in the fuel.

Tuning a six pak setup is a labor of frustration unless all of the components are in top shape, including wires, plugs, distributor, coil, and fuel distribution. Some old schoolers can whiz right through it, most people (including myself) can not. I’m learning tho, and am in the middle of rebuilding my entire setup. Currently waiting on the diaphragm rebuild kits to arrive, which are not included in any kit.

View attachment 1715518076
Click to expand...
Smart idea to use the plastic tote lids. Keeps those pesky springs and check balls at bay.
 
toolmanmike said:
Here's a Nicks Garage video of a 340 6 pack on the dyno. You will be able to see the outboard carbs open under full throttle acceleration. (starting at about 9:45 but you might find some tuning tips before that)
Click to expand...


T.M.M.

Thank you for the offer but I didn't bother to look at his video...
You can idolize him, you can put pictures of him over your fireplace, bedroom or mancave. As a mopar mechanic he is one the better ones up there North of the border but that does mean the rest of the package is worthy of all the adulation.....
We'll let this slide for now as I don't like to talk about fellow mopar fans on account of their menial characteristics.
You know the old saying, You can fool most of the people all of the time and you can fool some people some of the times but you can not fool all the people all the time.
So take a little, watch a lot and move along in life.
 
TUNING A SIX PACK

I just read this and I don't think I'll ever get my car to idle and not smell any gas ....
I know something is not being adjusted properly they were rebuilt last yr etc but it's really upsetting.

But guys I can't thank you enough for all the input.
MAPS
 
brian6pac said:
This is one I just put together, no bog here, pumps in all carbs
Click to expand...

Right!

I never liked the disconnected feeling between the gas pedal and the control of the outboards on my six pack motors, so I've always used the DC Performance mechanical Holley's.

I absolutely love the way the feel, look and perform. I'd never go back to the vacuum secondary stock versions unless it's time to build a trailer queen.

Using a permanently mounted wide band has made fine tuning these carbs a dream.

20200427_174153.jpg


20200427_174206.jpg
 
Lovely had those on my 70 Cuda V car loved the mechanics linkages I didn't even n know they had vacuums originally

What I'd like to know can you use mechanical linkages on the stock carbs ? Just remove the vacuum secondaries and go like that, can it be done ?
 
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