I have a 350 with a mild cam and a a jet with nozzle drip. I know the causes and I can't remember what size drill bit to use on the idle feed restrictions. Anyone have a link to a good on-line article on this subject?

First, just spray aerosol carb cleaner backwards through the air bleeds to assure they aren't partially plugged.

If you have a mild cam, I suspect you won't need to modify the carb to cure drip.

Do you have the vacuum advance connected to manifold vacuum? The increase in idle speed from the advance at idle would allow you to back out the idle speed screw. That alone might fix the drip.

I do have the vac advance hooked up to full vac. The cam is comp's 268 and it does have a little lope. Anyway, I want to remove the vac advance from full vac b/c it causes low RPM / low throttle missing - hook it to ported and it goes away.

Do you have the original carb or is it a later one? Pull the carb & see how much of the transition slots are showing with the throttle plates closed. You shouldn't need to drill out the idle feed restrction with that cam.

How does the idle screws affect the idle?

If you have about 10-12 initial & 10-12 vac. advance it shouldn't be a problem.

Originally posted by 68Malibu:
I have a 350 with a mild cam and a a jet with nozzle drip. I know the causes and I can't remember what size drill bit to use on the idle feed restrictions. Anyone have a link to a good on-line article on this subject? Start with .039" on the idle tubes. You may need to go to .041". Do you have the correct drills? Here is a link discussing sources for the bits. http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=9;t=015628;p=1


Mike

The off-idle discharge slots are fully exposed b/c the throttle stop screw is opened quite a bit. The idle mixture screws do still control the idle to some degree but not like they should.

Originally posted by 68Malibu:
The off-idle discharge slots are fully exposed b/c the throttle stop screw is opened quite a bit. The idle mixture screws do still control the idle to some degree but not like they should. Sounds like you might need to drill your throttle plates.

Mike

You should prob. open up your idle bypass holes you don't really want to drill the throttle plates because it's still going to be passing air through the veturis & the nozzle drip will continue.

Originally posted by 68Malibu:
I do have the vac advance hooked up to full vac. The cam is comp's 268 and it does have a little lope. Anyway, I want to remove the vac advance from full vac b/c it causes low RPM / low throttle missing - hook it to ported and it goes away. Full manifold vacuum to your vacuum advance should not cause any low rpm problems unless it is misadjusted. Have you checked to see if the vacuum advance plate is centered in the distributor? We've had low rpm misfire problems with vac advance caused by the plate rotating the pickup in an eccentric arc.