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  #31 (permalink)  
Old 04-20-2013, 11:48 PM
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Ngk BPR6S..........

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  #32 (permalink)  
Old 04-20-2013, 11:54 PM
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Once you get this sorted out the accelerator pump shooters may need tweeking.

Need another AFR trace at part throttle cruise. 40++MPH so you are truly on the primary main jets and not still driving on the idle circuit.
And then a nice 2nd gear WOT pull ,, rug it from low cruise/part throttle drive road speed to 6000rpm. in 2nd gear.
( first gear is too much wheel spin)

You then need to work on one area of the primary jetting at a time.
you cahnged both the cruise and the WOT at the same time.
one change at a time ,,, only. Work on only one circuit/driving mode at a time.

Then need a idle AFR trace at idle (neutral) idle in gear,, and then idle at 1500 rpm and idle at 2000 rpm and idle at 2500rpm
( in the drive way in neutral no load) ( idle and off idle transition circuit)
set the idle with a vacuum gauge for best idle quality, not afr. It will be RICHER than 14.7:1 at idle.
carbed engines idle at a AFR of 12.5:1 to 13.8:1. The priority is best idle quality and best idle manifold vacuum, not a specific idle AFR. Give it what it wants at idle...or you will never get the off idle correct.
Then: the off idle transition should be in the +/- 14:1 afr zone. 13's are fine at the transition.
This is off idle 1200 rpm to 2000++++++ rpm light throttle, before rth primary mains start up.

REMBER with dual quads you are mostly driving around ON THE IDLE CIRCUIT and off dle circuit
until you get really going (road speed and rpm)

You need to be able to identify which circuit you are driving on and tune only that circuit.
A vacuum gauge really helps.
Do not try to tune /correct the part throttle tune (primary rod lean step diameter ) and the WOT tune at the same time. (rod tip and main jet)

GET a vacuum gauge

Last edited by F-BIRD'88; 04-21-2013 at 12:22 AM.
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  #33 (permalink)  
Old 04-21-2013, 12:02 AM
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Fang16: Excellent advise from F-Bird has been given. Remember, change 1 thing at a time.
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  #34 (permalink)  
Old 04-21-2013, 12:06 AM
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The edelbrock carb tuning manual.
Volvord 784VC Edelbrock Carburetor
This is your bible.

You need to start with the right float setting/fuel pressure, spark plugs and spark advance
then set the idle (with a vacuum gauge)
The carbs will not tune right unless the floats are set right to start with.
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Old 04-21-2013, 12:09 AM
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Quote:
Originally Posted by 33Willys77 View Post
Fang16: Excellent advise from F-Bird has been given. Remember, change 1 thing at a time.
Thanks: The biggest skill you need is PATIENCE.
You will not get it all done in one day.
The manifold vacuum gauge is your best friend.
The AFR gauge is just a guide and WILL lie to you.
remember it just read the4 oxygen content in the exhaust.
not the true AFR.
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Old 04-21-2013, 12:15 AM
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When you do a AFR trace and post it. could you add information to the data trace showing, approx relative throttle position and or manifold vacuum and trans gear.
So I kow what you are doing at any one time beyond just time AFR and engine RPM.
Note pad will allow you to edit.
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  #37 (permalink)  
Old 04-21-2013, 12:28 AM
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Inovate AFR gauge/meter. It would be real nice to do another Free air calibration and
verify good wiring grounding of the meter etc. This is critical.
Garbage in ='s garbage out. Any all exhaust leaks will give false gauge readings.
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Old 04-21-2013, 12:33 AM
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when setting up the idle and idle in gear the power step up spring /primary rods must be down lean in the jets
at idle or the idle will be off. idle manifold vaccuum in gear. 3" or 4" step up spring should do it.
as a start.
Do not allow the engine to idle slow and "load up" when its cold.
Give it trpm while warming up. You need clean crisp spark plugs to get the throttle response
you are after. Don;t let the einge load up when its cold. RPM is your friend. while its warming up.
Please verify that the MSD is switching from cranking start- retard mode to run mode ... 36deg fixed idle timing at 500 rpm
and does not fall back down, when you go in gear.
and does not advance further with rpm.

Last edited by F-BIRD'88; 04-21-2013 at 12:39 AM.
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Old 04-21-2013, 12:43 AM
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List ALL the primary metering rods and ALL the primary and ALL secondary jets that you have on hand to work with/tune with.
power step up springs on hand too.
no use me suggesting a metering rod or jet you do not have on hand.
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  #40 (permalink)  
Old 04-21-2013, 12:47 AM
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What brand of spark plug is your preference?
It don't matter much to me...
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  #41 (permalink)  
Old 04-21-2013, 12:50 AM
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All most forgot you want to get both carbs set up the same at idle. fron and back carb Throttle position and idle mix screws
all set up evenly. Are you useing the PCV system or...?
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  #42 (permalink)  
Old 04-21-2013, 01:03 AM
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On the MSD box make sure all the stupid retard functions are disabled.
You only want a start cranking retard active. and it should swith at 500rpm and not switch back down if the rpm drops, once the engine starts. Verify this...and that all other step/launch/time bla bla bla retards are off/disabled.
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Old 04-21-2013, 01:08 AM
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make sure the launch and burnout rev limiter is off/disabled.
You do not want any of these bells and whistles active.
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Old 04-21-2013, 01:12 AM
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verify correct mSD box wireing and grounds. The engine must be grounded to the body of the car and the frame of the car. Ya it matters.
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Old 04-21-2013, 01:15 AM
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Make sure to save your settings to the MSD box before disconnecting the lap top.
Then verify the timing with a timing light.
This box has way too many bells and whistles. You do not ewant any of this crap active
other than cranking start retard.
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