I recently installed a Holley o2 kit to assist with carb tuning. So far it has helped me go from a severe lean during cruise to stoic, BUT I am still unable to get the idle straightened out. I am seeing an Air/Fuel Ratio of 14/15 during cruise, 1800 rpm+, BUT am seeing 19/20 during idle @ 1200 rpm.To get the car to idle in gear @ 800 rpm, I have to turn the in park idle up to about 1200. It does not like to idle in gear below 800, I also noticed that the idle jumped about 400 rpm when restricting the air flow. The idle mixture screws are about 1.0-1.5 turns to get a vacuum of 12, beyond that makes no difference. Here is the setup. - Motor is 462 with S1 ported heads, cam is 234/242..520..110+4, B4B intake, ported exh manifolds @590cfm each, 2.5" duals with x-pipe. 200r4 xmission with lock up. - Carb is 7041540, primary 78 with 47 rods, secondary 'F' hanger with DU rods - Pertronix ign with Blaster 2 coil, initial timing @ 8, vacuum advance hooked up (during idle/cruise) - Engine vacuum on idle is 10-12 I have a plethora of rods and jets that I can use. (Rods-41/44/45/46/47) (Jets-72/73/74/76/78) I believe I need to use a smaller rod to allow more fuel at idle. Suggestions on rod size would be appreciated?
Bob, were the idle circuits modified in the main body? They are probably about .033 original, and based on your cam and compression I would probably drill them to .036 or .038. I would also open up the down channel restrictions plus the upper/lower main airbleeds. Possibly the upper idle air bleed as well. Part of the problem, without this, is the engine won't idle on the idle circuits. It requires you to turn the idle screw to open the throttle blades and it begins to pull from the main circuits, which, at idle, doesn't calibrate correctly. I would also try a 75 jet with a 43B primary rod.
Hi Mark, Thanks for the advice. I'm glad we got to discuss my issues. Since I have no idea how to accomplish what you are suggesting I will be sending my Carb to you for the modifications.
