Hi everyone,

so I got my wb installed in my 76 firebird strip car, I was wondering if anyone has any link for info on tuning a carb using a wb. At the moment , I kinda realized that my ratio at idle was approx 12.38:1, so i changed it to about 13.4:1. But on light throttle blip I was like around 11:1 which I think would be way too rich. Car is kinda new on engine, think I might need to play a bit with jets. Any website with details would be really good, or just any tips. thanks

Math

 

Ignore that the guage says when you "blip the throttle"
you're likely reading the AFR as the motor is decelerating
and returning to idle with the throttle closed. ( not very relevent)
A idle AFR of 12.5 to 13.5 is acceptable for a "race car"
you won't get it to idle (well) at 14.7:1 so don;t try.
watch the guage as you cruise around. You want to get at or near 14.7:1 while cruising and between 12.5:1 and 13.3:1 at WOT. What ever gives you the best MPH on a time slip is the right AFR ratio at WOT for YOUR MOTOR.

 

What to change to effect different driving modes on a Holley carb.

Engine temperture will effect the AFR's. a cold engine will want more fuel than one that is fully warmed up.

idle AFR = idle mixture screws.

idle and off idle low speed cruise 0 to 25MPH =idle feed restrictions, idle air bleeds.

Part throttle cruise above 25mph = primary main jet.
power enrichment timing = power valve vacuum rating.

WOT power AFR = primary and secondary main jets.
IF after finding the optimium WOT jetting, the cruise jetting is too lean or too rich, you can calculate the difference in jet area and enlarge or reduce the size of the power enrichment orifices accordingly (remove the power valve to see them) and rejet.
before you do any tuning to the idle circuit be sure the throttle blades are properly positioned at idle speed reletive to the idle transfer slots. (neither too far open or too far closed.) You can adjust the idle speed if nessessary without changing the throttle position at idle by increasing or decreasing the ignition timing at idle and or creating a auxillary idle air bleed (like a PCV valve) to allow more or less air into the engine at idle.
Just about all carbs with a 3/8" vacuum port on the base are designed to use a PCV system and will idle rich and with the throttle blades out of position at idle unless the PCV is hooked up.

 

thanks, will start check that out pretty closely. Need to get transmission together and I'm off to the track.

MAth