Race Demon questions

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furyus2

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I have a 750 Race Demon. Works great. It's on my 64 Sport Fury 440/ fmvb 727/ 3.91 rear. 3k stall convertor. I was told a long time ago that the race demon was rated smaller than they really are. Like my 750 would be an 800cfm. Is this true? How would this carb work on a 500 ci stroker? Also, I was expecting to see that air idle adjustment in the center of the carb when I rebuilt it. There was a plug in there instead. anyone have any thoughts? My questions are for a race demon only. Seems they don't offer this carb anymore.
 
It's not that they're rated 'smaller', they were wet-flow rated as opposed to other brands(holley). It gets way more technical but the quick and dirty is that a wet-flowed 750cfm carb has a real-world flow capability about equal to a larger carb that was dry-flowed. If I remember the difference for gasoline was somewhere around an 8% difference and quite a bit higher for alcohol(approximately double maybe). As far as the 'idle-eze' jet down in the carb base, I have no idea why someone would plug it when you can just screw it closed, unless someone stripped some threads. Easy enough to pull the basepate off and inspect it. They are nice for pulling a little extra air ar idle without opening the blades too much(or drilling) if your engine needs it. Now just my opinion, but a 750 flow rated any whichaway ain't gonna cut it on a performance 500 cube engine. It'll work, just won't be optimal. I use an older 850 demon on a mildly built 440+.060 and once I got it all dialed, added adjustable bleeds etc it kicks the crap out of the 750 QF that I have. The QF was great once tuned in, a good unit, but the big demon is just performing better and I feel it when driving. It is a bit more finicky though especially in colder (CA lol) weather but I don't mind..
 
750 demon flows around 830. The venturi is around .1 larger than a QF or Holley 750. If your racing the 500 an 850 demon or larger would be the better choice. If a streeter the 750 demon will work with instant throttle response.
 
Thank you both for very intelligent, thoughtful answers. No, I'm not joking. The engine will be mostly a streeter. Probably 90 %. This carb works so well, that I hate to change it. Second question. Which would hold back performance more on my 500 stroker, the race Demon, or 1 3/4 inch headers. Which would you change first?
 
My car has mild built 470 stroker. Had a 750 AED on it. Tried a 1000, picked it up 2 1/2 tenths in the quarter mile. I would like to try a dominator on mine. Kim
 
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I have a demon rs, with three sets of sleeves. A regular Holley 750 dp, 4779 has 1.375 venturi, 1.687 throttle. My red sleeve, rated 750, is 1.400/1.687. Blue, rated 775cfm, is 1.425/1.75. Gold, rated 825 cfm, is 1.500/1.75.
I bought mine from a friend who told me it was 850 cfm with the blue sleeves (I'm sure he thought it was, he wouldn't have lied to me). Took it off his 408 off brand, put it on my 406, went a best of 6.32/108 without ever taking the bowls off. I was happy the way it worked.
The gold sleeves and downleg boosters would go in, if it was on a bigblock.
 
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