Idle Problem

[CUDA JAS]

yep, something to try first

I found a good way to determine if you have the primaries to far open and too much of the transfer slots uncovered, without taking the carb back off the car,  is to check ported vacuum.  Put a gauge on the port above the throttle blades, if there is vacuum there at idle, you likely have the primaries open to far.

I found that issue with my carb, cracked the secondaries a little, closed the primaries so there was no more vacuum above the throttle blades.  Seems to have created a better quality idle on my 360.

Jason

[cudabob496]

I found a good way to determine if you have the primaries to far open and too much of the transfer slots uncovered, without taking the carb back off the car,  is to check ported vacuum.  Put a gauge on the port above the throttle blades, if there is vacuum there at idle, you likely have the primaries open to far.

I found that issue with my carb, cracked the secondaries a little, closed the primaries so there was no more vacuum above the throttle blades.  Seems to have created a better quality idle on my 360.

Jason

Good idea. My long duration cam may make it no so obvious, as far as what vacuum number is the correct indicator.

[cudabob496]

OK, think problem is solved for now.
Put a new cap on the vacuum port tube coming off the primary
metering block. But the cap is still a tad loose, so instead I installed
as small screw and sealed around it with RTV. There definitely should not
be any vacuum leakage now.
checked all my 4 corner idle adjust screws to 1.5 turns open.
Increase main idle adjust screw 1/4 as well.
Idles nicely now at 1100 rpm.
Still need to verify timing, though I did vary it a little, up and down, with my MSD timing
control module, and it did not make much diff in idle rpm.
Thanks for the help!