so i rebuilt my bbd lastweek out of boredom and wrist injury. did it all right and got everything adjusted perfect and it runs awesome. anyways, i keep lookin through the kit instructions and diagrams if i need to fine tune it. the stepup piston spring/hex adjustment doesnt make sense when the whole sweep of the metering system is waaay adjustable. everything ive seen emphisizes on how not to touch this hex or adjust perfectly.
im missing something...

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

bump, im still wanting to know if anyone has insight

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

Not for sure what your asking. But yes the piston and metering rod assy is ajustable. Basically the higher you ajust the rods the quicker the main system richens up. The spring can be changed also to help effect when this rod assy raises up. What it does if you look at the rods close they are stepped, when you raise the rod to where the smaller step is all that is down in the jet it lets more fuel flow through the jets.

If it runs good your probably where you need to be. IF it seems to use ot much fuel you might try lower the rods, if it hesitates at any part throttle piont you might try raising them. Even if neither problem is there raising them might bring in a little part throttle power, but you hit a piont that it will start using more fuel on a cruize. Its really something that you need to expeirament with and try going lower & higher and see how it effects you setup, if you find a better piont that works with what you want and gives no problems run it. Just make a note of where you start out so you can go back if it causes probelms.


Jess

well why have the stepup adjustment AND the hex spring adjustment. it just seems they both do the same thing. unless the hex is more for a finer tune?

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

The step up adjustment is made when the step up piston assy is all the way down with the throttle completely closed and the idle speed screw is backed off. The step up rocker should not be lifting the assy.
The hex adjustment is how far the rods are out of the jets when the throttle is closed and the step up assy is all the way down.
First you adjust the hex, then the rocker.

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Slant Cecil

Carter BBD operation and repair manual (pdf)

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

yea i got the manual, this is where im gettin this confusing info. isnt the mixture screws gonna be controlling most of the gas at idle?and the adjustment at top would still adjust the metering at idle, right? so y have this fine tune adjustment when the rocker has sooo much play to set. ya you do an intial setup wit throttle closed and wut not.

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

Piston needs to be at bottom to compress the vacuum step up spring.Raising the piston reduces spring tension reducing the springs ability to push up metering rods under low vacuum.

ha, nice! thank you, leave it to the newbie to answer, sigh... so this hex adjustment would be adjusting the spring tension for when to push back up when vacuum drops? huh
well they shouldnt have the adjustment be made wit clearance, but wit inch lbs gauge.

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder