The 4779 style holley I bought from a friend came with a VERY weird jet setup. On each float bowl their are two holes and a set of idle screw looking needles that go all the way into the metering block inside the carb, to take the place of the jets.....anyone ever seen this setup? Thing is, even though the carb works great, I can tell by the plugs and the exhaust coloring that its running pretty rich....does anyone know what increments the turn of a needle does on this setup?

------------------
Nice car: 1988 Formula 355, mildly ported/polished Vortec heads, RPM intake, Comp Cams Extreme 268 cam, 650 Holley double pumper, 5-speed/3.73 Richmond gears, and N02 on the way
Old 1/4mile: 13.5@105mph

Evil Car: 78 Pontiac Grand Prix, 500inch caddy motor, edlebrock intake,HP Holley 750 DP race prepped carb, B@M TH350 tranny, 16inch Iroc-Z rims, blacked out chrome, soon to run 10's...

There's no replacement for displacement!

 

this wont help much but it sounds like you have an adjustable metiring block. this makes tuning a carbs metring system a breaz.
i would try contacting holley for more info.

------------------
when the green flag drops the bull$hit stops

350,performer RPM intake ,650dp, 700r4, headers, 3inch exhast