Speed Demon vs. Road Demon

86GT · 01-20-2003, 11:44 AM

I'm thinking of running a Road Demon 625 carb (getting rid of the 650 Holley DP I currently have). I was also told to consider the 650 Speed Demon as well. I'd like to hear some opinions on both.

red82gt · 01-20-2003, 11:33 PM

The road demon will have a leaner calibration than the speed demon for normal driving. The speed demon can also be had with mechanical secondaries. If you want more performance-speed demon, if you want more driveability-road demon. The main difference is that the road demon has smaller main jets and larger power valve passages so that it is leaner at cruise and part throttle and then the extra fuel under load comes from the power valve. The speed demon has larger main jets and smaller power valve passages so it gets less of its fuel from the power valve and more from the main jets.
Why are you getting rid of the Holley 650 DP?

01-20-2003, 11:44 AM	#1 (permalink)
86GT Sniffed too much n20 Join Date: Oct 1998 Location: Ont, Canada Posts: 1,018	Speed Demon vs. Road Demon I'm thinking of running a Road Demon 625 carb (getting rid of the 650 Holley DP I currently have). I was also told to consider the 650 Speed Demon as well. I'd like to hear some opinions on both. __________________ 2002 Windsor Weekend Q16 Qualifier

01-20-2003, 11:33 PM	#2 (permalink)
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,508	The road demon will have a leaner calibration than the speed demon for normal driving. The speed demon can also be had with mechanical secondaries. If you want more performance-speed demon, if you want more driveability-road demon. The main difference is that the road demon has smaller main jets and larger power valve passages so that it is leaner at cruise and part throttle and then the extra fuel under load comes from the power valve. The speed demon has larger main jets and smaller power valve passages so it gets less of its fuel from the power valve and more from the main jets. Why are you getting rid of the Holley 650 DP? __________________ F4TE 351w block 393 stroker: Scat 3.85" crank, scat H beams, Probe SRS pistons, Proformed 750 DP holley, Vic jr intake, AFR 205's, Buddy Rawls hydraulic roller cam, Crane 1.6 Gold race rockers, Powerforce SFI balancer, centerforce steel flywheel. Kooks 1 3/4" headers, Spec stage III clutch, Dr. Gas 3" x-pipe, spintech pro streets, TKO-600, Moser 31 splines, Detroit Locker. Just about back on the road...

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