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reborn55 09-20-2013 09:28 AM

holley 600 help
Sorry to bother with stock carb question, but can't seem to get Holley to answer emails. i have a 6979-1 obsolete 600 holley(looks same a 1850). It is on 48 Chevy with 350, edelbrock intake, hooker hedders--nothing fancy. Problem is I cannot set the idle jets. Turn them all the way in and does not affect the idle--rebuilt the carb using Holley kit and still no luck--has the floats adjusted properly. Idles smooth at 850 in park--(19 inches vacuum) and 550 in drive with the air on. No rich fuel smell--performs well--so stumble-surge or stall. Have pulled the needles out and a little fuel will come out--is it possible that I need a new metering block or just don't worry about it. thanks for your time. :)

jmarksdragster 09-20-2013 04:05 PM

Pull the carb and turn it over, make sure you don't have the throttle blades opened too far exposing too much of the transition slots. This will allow fuel to feed from the t-slot making adjustment with the mixture screws ineffective. The picture blow show a normal exposure, they should show about .020 or look like little squares showing.

oldandtired 09-21-2013 06:02 AM

There were some carbs in their product offering that worked "backward".
You turn the idle screws counter clockwise (out) to lean the mixture.

This carb also had the double power valve - a little bit for hills and a big shot for passing.

reborn55 09-21-2013 07:29 AM

Mark--I have checked that and they look like your picture

Knew it had that power valve---will have to go back and see if I changed it to a single one. didn't know about reverse settung

levisnteeshirt 08-24-2016 08:38 AM

One of the power valves may be stuck open , cycle it with your finger , look at the metering block , eye level with the mixture screw, see if there is a brass restrictor in the second hole over from the power valve on each side, and see if u can find the diameter of the hole ,, check the idle air bleeds at the top ( google a pic ) toward the outside and see if they are blocked

aquilesopkarg 07-14-2021 02:27 AM

This carb also had the double power valve - a little Speed Test bit for hills and a big shot for passing.

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