i have an early 90's roller motor L98. Stock long block. .480 lift cam, HEI distributor, plugs gaped to .045. Shorty headers with a 3in catback exhaust custon ypipe. AIR SMOG AC delete

The intake manifold is a holley street dominator with an open plenum. 1 inch carb spacer. and a holley aluminum avenger 670 vacuum secondary carb with the 4 corner metering block adjutment. brand new carb.

The idle screw is maxed out when lowering the idle. ive been advancing my timing which has caused me to have to lower the idle. Any help?

 

First, make sure the throttle cable isn't holding it open. Next, you may need to adjust the secondary idle screw. Not sure where it is on the Avenger series, but on the older Holleys you have to take the carb off and flip it over to see the secondary screw. If neither of these helps, then you may have a vacuum leak and a carb that was running a little too rich. This would make it act like the throttle is open more than it actually is.

What is the timing set at?

 

actually i just lowered the fast idle and that seemed to help. it allowed me to lower the curb idle to what i needed

 

Advancing the timing has the effect of upping the idle speed. You must mean retarding the timing....?

 

If your fast idle screw is engaged when the engine is warm then you choke is not properly adjusted or the wires are not hooked up. That is why the fast idle is on.
You need to adjust and or hook up the wires on the choke, not turn the fast idle screw.

 

Correct. You shouldn't really be making these adjustments when the engine is cold, and when the engine is warm enough to be adjusted, fast idle should be completely off.

The OP was correct. Every engine I have ever worked on, advancing the timing increases the idle speed. Engine idle speed is simply the equilibrium point where internal friction within the engine matches the power output of the engine. This is why idle drops when you put the car in drive. You just added a lot more friction/load to the same amount of engine power. As you advance timing at idle, combustion becomes more complete, resulting in the engine producing more power with the same amount of air and fuel input. As engine power goes up, idle speed increases until increased friction within the engine balances the increased power. As you retard timing, you reach a point where combustion becomes so poor that the engine ceases to make enough power to overcome its own friction. It lugs up, stalls, and dies. It gets a lot more complicated than that when you look at increased cylinder pressures and temperatures with timing advance, but it all in effect lends to the engine making more power and speeding up.

 

yes advancing the timing did bring the idle up, thats why i had to lower it back down with the curb idle screw. In case i wasnt clear