I haven't really posted much, because truthfully my 496 was running fine, so I didn't need help with anything!
Well a few months back I decided to swap a tri power setup onto my 496. Finally got everything buttoned up 2 weeks ago between house projects, but am having some issues.
my setup:
3 brand new holleys. all based off the 2300, center is 4055 and outers are 3659s. this is the new repop of the 1968 427/435 carbs from the vette. I did add an AED metering block to the center carb, and I have AED jet plates for the end carbs if I need to rejet them.
MSD ignition- pro billet distributor (no vacuum advance) with 6AL box. currently set at 20 degrees base timing with 18 advance.
using innovative Wideband o2 for tuning.
here is my issue: every part of the carb setup seems to function as it should EXCEPT the idle.
AFR ratios from last night short drive:
idle- around 14 (bounces from 13.7ish to about 14.5)
part throttle accel- between 12.5 and 13
WOT- between 11.5 and 12 but need to do more driving before changing.
the carbs still have the original divorced choke setup, which according to documentation originally had a fast idle of 2000 rpms.
right now if I jump in the truck pump the gas to set choke, it will start and idle around 750 rpms. once warm I can hit the gas knock it off fast idle down to regular idle around 650.
idle AFR is around 14. mixture screws about 1- 1 1/8 turns out. I drilled 2 3/32 holes in the center carb butterflies. originally had transfer slot set a .020, had to bump throttle 1/2 turn to get idle up.
I should note- I have NO adjustment on the outer carbs idle circuits. it is fixed and not adjustable.
to me, it seems like I need to bring my rpms up, but also need to back down my transfer slot. my question- how to accomplish this? Do i need to make larger holes in the primaries to let more air in? Would swapping in a distributor with a vacuum advance help to add more timing at idle, thus increasing rpms?
Well a few months back I decided to swap a tri power setup onto my 496. Finally got everything buttoned up 2 weeks ago between house projects, but am having some issues.
my setup:
3 brand new holleys. all based off the 2300, center is 4055 and outers are 3659s. this is the new repop of the 1968 427/435 carbs from the vette. I did add an AED metering block to the center carb, and I have AED jet plates for the end carbs if I need to rejet them.
MSD ignition- pro billet distributor (no vacuum advance) with 6AL box. currently set at 20 degrees base timing with 18 advance.
using innovative Wideband o2 for tuning.
here is my issue: every part of the carb setup seems to function as it should EXCEPT the idle.
AFR ratios from last night short drive:
idle- around 14 (bounces from 13.7ish to about 14.5)
part throttle accel- between 12.5 and 13
WOT- between 11.5 and 12 but need to do more driving before changing.
the carbs still have the original divorced choke setup, which according to documentation originally had a fast idle of 2000 rpms.
right now if I jump in the truck pump the gas to set choke, it will start and idle around 750 rpms. once warm I can hit the gas knock it off fast idle down to regular idle around 650.
idle AFR is around 14. mixture screws about 1- 1 1/8 turns out. I drilled 2 3/32 holes in the center carb butterflies. originally had transfer slot set a .020, had to bump throttle 1/2 turn to get idle up.
I should note- I have NO adjustment on the outer carbs idle circuits. it is fixed and not adjustable.
to me, it seems like I need to bring my rpms up, but also need to back down my transfer slot. my question- how to accomplish this? Do i need to make larger holes in the primaries to let more air in? Would swapping in a distributor with a vacuum advance help to add more timing at idle, thus increasing rpms?
