Friends 1980 Vette which has a few mods. Starts up great, warms up and idles nicely. Problem is, as you rev up - no load, parked, and look down the primary barrels, there is a hesitation from idle to about 2500 revs when the gas suddenly starts to flow from the main jet rings. From idle to 2500 is leans out, not dying, but close to it. As soon as the main jets start to do thier job, it picks up like you would wish - fantastically.
Done full tune up of ignition and rebuilt carb, float levels, etc.
Unless I got it wrong, The main jets are a progressive syphon of juice from the float bowl to the discharge rings........ so, barring blockages, there is nothing to adjust or tinker with....
Someone put me straight please.....
Its the Holley with a gas pipe at the side between the bowls, not a centre hung type.

Well I have been having problems with my Rochester so I have just ordered a Holley, so no experience with it yet! Couple of ideas, have you checked the vacume at the manifold, could be you have leaks and not geting enough vacume at lower RPM, should be 15-20inches. Also try the Holley web site, I think they have a tech question area where you can email them your problems, thay should be able to sort you out.

Did vacuum checks in the past, but will do again, just in case, thanks. Any link to Holley site - did not know of its existance.

It's www.holley.com
Good luck!

Most hesitations are caused by the accelerator pump. Either the shot is late or soft. Engine off, air cleaner off, look down the carb and start to move the throttle linkage. As soon as it starts to move the accelerator pump discharge nozzles should begin to squirt. Check the accelerator pump linkage and make sure it's tight against the lever.