Check the brass tubes where the idle mixture screws seat, if that is messed up, you don't have any hope of tuning the idle. Depending on how the screws were damaged, those brass tubes could be damaged too.

 

I agree with Elliott on this. It doesn't take much to ruin that brass tube. Another thing to check is the cork gasket that inserts in the hole where the needle goes. That acts as a seal for the idle screw and sometimes can leak or cause the needle to turn when idling. Those needles should only be tightened to where it barely bottoms out with little or no pressure, before making your adjustments.

 

Make sure your air bleeds are clean. Use some carb cleaner and shoot some down the bleed.

Later, mikey

 

If the following suggestions don`t solve the problem, with the engine at idle shine a light in the carb and check for fuel leakage out of the boosters. If you see fuel coming out of the boosters at idle then either the float is set too high, the needle is stuck open or the fuel pressure is too high. If no fuel is coming out of the boosters shut the engine down and see if you see white smoke coming out of the carb, this will indicate it`s flooding out of the idle circuits which means the fuel pressure is too high. either way, it`ll cause the idle circuit not to respond.

 

I have also seen gorrila-wristed people turn the screws all the way in so far that the needles actually cracked the base of the carb!

Two cracks from where the needles enter the primary tubes down to the base of the carb. You'll have to take the carb off an flip it over to see it, but I've seen a few times :nono:

 

I guess I'll go back to the old holley carb that I replaced for this, it's a little big but that's ok

 

IMS 1406 carb

Don't give up yet! The previous responses are all on track, ck to see if the IMS holes were damaged if this does'nt work. I have a 1406 and had the same problem with no response from the pax side screw when adjusting. Try this to clear the "holes," it worked great for me and now I've got the carb "dialed in". 1. Remove both screws 2. Cover carb with a rag 3. Spray carb cleaner in the "holes" with the small tube that you attatch to the spray nozzel working the tube in and out as you spray 4. I blew @ 40psi into the holes and put my hand over the rag ontop of the carb so it did'nt blow off. 5. Install the screws, seat them lightly and then back off each one 1.5 turns 6. Fire it up! and then adjust for highest vaccum at a given idle RPM. You should have a deffinite response anytime you turn the IMS.

Good luck,
Roy