Need advice from Carbhero´s!! 383 with 750....

[Olle B]

Trying to take the best out of my Challenger with 383.
Cant really understand what happens under the hood even if I think I have a clue!!
Started with way to dark close to black plugs,,with my new factory Holley 750 vacsec carb.
Changed from original 72 to 70 main,, still black.
Change the powervalve to 85 from 65!!
It was an advice from my speedshop to make the car respond even better to pedalforce and still not overrate the fuel.
The theory was a little more open throttle will cause more air and lean out the mixture.
I should also switch back to original 72 to make it move at full throttle!!
Now its very light on the isolators,, close to white!
I have approx 12" Hg at idle.
The car acts well ,, but what is good compared to perfect??
I have also swapped the distributor springs to light preasure versions and that really was a kick in the right direction!.

Q´s.
Are the idle setting adj screws having any affects on the plugcolor?

Are the theory wrong,, should I swap the valve?

Is it possible I need 74 or bigger mainjets??

Shall I drill the throttleplate holes??.
The (funny) thing is that still the plugs indicate lean,, the idle is causing "wet eyes" and a high level of "fuel smell" !!

What way shall I go,, The jets and valves arent that cheap in Sweden,, so I better start in the correct direction!!

PLEASE!!
Best R Olle B

[img]http://mediaservice.photoisland.com/auction/Jul/2003746511748729233688.jpg[/img

[jelsr]

Olle,
Maybe a little info will help you understand better. The number on the power valve is minimum vacuum reading to keep it closed. The 85 in your case means it will open when the vacuum goes below 8.5 inches. When open it allows extra fuel to bypass the main jets. The idle screws will have an effect on plug color, usually start at 1-1/2 turns. Plug readings are taken when vehicle has been running at good speed then shut off and coasted to stop without any idling. Idle mixture usually makes plugs darker.

[Olle B]

Thanks
I have the idle screws set on max 1 turn.
The color was measured after normal driving without any longer period of idle.
Are 72 main jets a "thin" number to a slightly hotted 383??
Best R Olle B

[jelsr]

Don't know the altitude at your location, but the closer to sea level the fatter (rich) the mix. It's better to start rich and work your way down, too lean can damage parts. Try the screws at 1-1/2 and use your vacuum guage to fine tune them. None are exactly alike Olle, I've seen em with 76's.