I am currently trying to tune a mild 355 chevy on my 1991 pickup.

I have vortec heads, a Large single plane intake, cam, and 9.5-1 compression, nothing too crazy.

I have it idling at 14.7 afr, and i have it light cruising at about 14.7(which is right where i want it). But when i am rolling highway speed (70-75 with 29 inch tires and 3.08 gears, 2000 rpm), and let off the gas the afr goes way down to about 12.1-12.4. Even when light cruising, the AFR goes to 13.2 when i let up off the throttle. I assume this is because of the high change in vacuum, but is there any way to adjust the deceleration of a carter afb/ edlebrock carbuerator?

Also, when i let the truck sit a day or two, it is a pain to start. No matter how many times i pump it, i have let it crank atleast 10 seconds 3 times before it starts up. Is This because of the single plane intake, or is something else going wrong? I am also using a highflow k&n openelement air filter. Could the gas be evaporating out of the open element?

Any help or advice would be greatly appreciated
-Evan

 

Going rich on deceleration is somewhat the nature of the beast with carbs.

How is your choke set up?

 

I was afraid of that, i am new to carbs but have fooled with tuning tbi on the same engine for the last year.

I have an electric choke, turned all the way to the richest setting notch, but i can rotate more. today at about 70 deg it warmed up from 14.0 to 14.7 once the choke opened, and once it decided to start.

-Evan