Big Chief screw blower tuneup

Several guys were asking me about a baseline tuneup. This went 4.0@183@2650lbs and has been safe.

540 14 degree chevy with indy manifold and .850 lil bertha.
Pump 14.89 GPM @165 psi

port nozzle 1-66 2-50 3-66 4-66 5-63 6-63 7-60 8-66
hat 2-87 and 2-85 with spring checks
idle check 18 lbs
port check 26lbs
pump loop 90 jet at 15lbs
main jet 65@2000ft
set idle to .69 gpm@1800-2000rpm
D rotor@100%OD

For 125% I blocked the pump loop completely and ran the same tuneup otherwise.

Don't be afraid to dump a bunch of fuel on the starting line...like .160 jet. I idle at about 1000 degrees and average 750 on the two step.

I suggest a 330ft shot to check the plugs. Every combo is different.

good luck
Mike