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Six Pack secondary opening rate tuning

Posted By: 471Magnum

Six Pack secondary opening rate tuning - 03/29/10 05:09 PM

Working on getting the bog/surge out of my Challenger when the secondaries kick. Pulled a diaphragm apart to confirm what springs are in it (yellow).

In the process I got to wondering why no one has come out with a quick change spring kit for these, or better yet, an adjustable pod like the QuickFuel set-up for four barrels.

Seems like the latter wouldn’t be too difficult to implement on a Six Pack. Just need some sort of adjustable bleed before the Tee on the vacuum hoses.

Anybody tried anything like this?
Posted By: hemi68charger

Re: Six Pack secondary opening rate tuning - 03/29/10 06:50 PM

Quote:


...In the process I got to wondering why no one has come out with a quick change spring kit...

Anybody tried anything like this?




They used to sell the secondary diaphram spring kits back in the day...
Also, I found this..
http://www.quickfueltechnology.com/main-body-parts/quick-set-adj-sec-housing.html

http://www.quickfueltechnology.com/main-body-parts/vacuum-secondary-spring-kit.html
Posted By: calrobb2000

Re: Six Pack secondary opening rate tuning - 03/30/10 02:28 AM

hi
need more info !

engine , cam, vacuum at idel , ignition timing inital, total , advance rate,center main jet size , power valve no.
Posted By: BergmanAutoCraft

Re: Six Pack secondary opening rate tuning - 03/30/10 04:05 AM

Slow them down. People always think they need to be opened quicker.
Posted By: lewtot184

Re: Six Pack secondary opening rate tuning - 03/30/10 01:30 PM

Quote:

Working on getting the bog/surge out of my Challenger when the secondaries kick. Pulled a diaphragm apart to confirm what springs are in it (yellow).

In the process I got to wondering why no one has come out with a quick change spring kit for these, or better yet, an adjustable pod like the QuickFuel set-up for four barrels.

Seems like the latter wouldn’t be too difficult to implement on a Six Pack. Just need some sort of adjustable bleed before the Tee on the vacuum hoses.

Anybody tried anything like this?


i danced thru this last year. my problem was fuel pressure/volume. do a test. also check float levels and filter restrictions. the opening rate will change about 300-400rpm per spring change. every change to a stiffer spring above the yellows will about a tenth to the e.t.
Posted By: Mr.Yuck

Re: Six Pack secondary opening rate tuning - 03/30/10 01:35 PM

I just bought the kit of springs. I'll be taking them to the track and seeing which works best.
Posted By: sixpackgut

Re: Six Pack secondary opening rate tuning - 03/30/10 07:55 PM

if you would put a 50cc pump on the center carb and a 35 squirter, most of your troubles and wasting time changing springs would be over.
Posted By: BSB67

Re: Six Pack secondary opening rate tuning - 03/30/10 11:49 PM

Quote:

I just bought the kit of springs. I'll be taking them to the track and seeing which works best.



This is the only way to get the opening rate correct for max power. Tuning to eliminate the hesitation on the street, especially from a roll, may not result in max track performance.
Posted By: BSB67

Re: Six Pack secondary opening rate tuning - 03/30/10 11:55 PM

Quote:

...every change to a stiffer spring above the yellows will about a tenth to the e.t.



Lew, I think I know what you are saying here, but it might not be clear to others.
Posted By: 471Magnum

Re: Six Pack secondary opening rate tuning - 03/31/10 12:34 AM

Just to be clear, I have the knowledge and experience to tune through this issue. I know it's just a matter of heavier springs or tweaking the pump shot (or maybe fuel starvation).

I'm just looking to make the spring swap easier/unnecessary. It's very difficult to open up the pods without tearing the diaphragms. I grease the screws on reassembly to help prevent snagging/tears, but they happen, and diaphragms are $30.
Posted By: jbc426

Re: Six Pack secondary opening rate tuning - 03/31/10 09:56 AM

How do you have your ignition timing set-up? What's your initial and how much mechanical do you have? When does it all come in by?

Check your float levels. Where do you have them set at?

Do you have any vacumm leaks anywhere at all?
Posted By: B5 Bee

Re: Six Pack secondary opening rate tuning - 03/31/10 02:17 PM

It's not just the spring that controls secondary opening, the kill bleed also has a part in when the end carbs open.
Basically, the kill bleed controls the RPM when they start to open, the spring controls the opening rate (how long they take to fully open).

It's doubtful your bog/surge problem is the opening rate, it most likley one of these;
Not enough accelerator pump shot
Not enough initial timing
Sticking throttle plates
Clogged air bleeds or main circuits in the carbs
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