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HP 750 & Weiand Supercharger
I just installed new 750 HP on my SBC with a Weiand supercharger. Setting the air fuel mixture screw as per Holley recommendation. Only one screw has effect on the idle, but I went ahead and set all the screws as described by Holley. The vacuum reading directly from the manifold is 5 inHg steady in park & drive. The AFR is 11.2 to 12.5 and the exhaust smells rich, but no black smoke. The highest vacuum I got playing with A/F mixture screw is 5.5 to 7.5 inHg, and the AFR is 12.3 to 13. Which vacuum reading I deal with, the steadiest or the highest? The power valve on the carb is 10.5, shall I change it to 2.5? What can I do to get AFR mix between 13.5 to 14? Please help. Thanks.
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Check the ignition timing advance at idle. Blower (supercharged) engines require more initial timing and less total timing than naturally aspirated engines.Originally posted by mossman View Post
They also like a short, yet quick ignition advance curve and retarded timing while cranking to start.
Excessively retarded ignition timing is the most common cause of glowing exhaust headers. Headers glow red because there’s fuel burning inside.
The two main reasons are a faulty A/F mixture (most likely too rich) and retarded ignition timing; which doesn’t give the fuel enough time to burn
inside the combustion chamber. Are you sure the ignition timing synchronization is correct (LINK)?
http://blog.raceology.com/2003/05/10...-debunked.html (Don Terrill, Former NASCAR Engine Builder - Read Myth #7)May God's grace bless you in the Lord Jesus Christ.
'92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, Eagle 3.470" forged steel crankshaft & H-beam rods, Wiseco 4.200" forged pistons, Trick Flow Twisted Wedge 11R 205 CNC Comp Ported heads, 12:1 compression ratio, 232°-244° duration/.623" lift/114° LSA H/R camshaft, Trick Flow R-Series FTI Comp Ported intake, BBK 80mm throttle body, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima 34/78 Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal Dual 12" HP 3168 CFM fans, Frostbite 3-core aluminum radiator, Pypes SS dual 2.5" exhaust, SS off-road X-pipe, SS shorty headers, OEM smog pump converted vacuum pump, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, highly modified Ford 4R70W transmission, FTI 9.5"/3000 stall/triple disc TCC, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.73 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires. -
Oops sorry, I was in a hurry because the first writing disappeared after writing for about 1/2 hour. OK, Initial timing is 30°, total set at 30° at 3500 RPM.
Ignition is MSD 6A, distributor is MSD no vacuum advance. Heaviest spring for the advance weight is used. MSD boost retard.Comment
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