BG tech support recommends their 650 mighty demon for my car, here are the specifics.

383
9.82:1 flat top hyper
Dart Iron eagle 200's ported to 208's
Edelbrock RPM performer
Edelbrock 110gph fuel pump
Comp XE284h,(cam is 240I & 246E @ .050) 1.6 roller rockers
1 5/8 headers, 3 in collectors, 2 1/2" x pipe sytem.
700r4, 2800 stall, 3.73 rear
Car is used as cruiser, occasional strip, fair weather only, not a daily driver, I can live without a choke.

I was thinking 750cfm, what do you guys think?

Personally, I think the 650 will be a little more responsive on the street, but you'll be leaving some performance on the table at the track. For a street/strip deal it's hard to beat a 750 VS. At the track my box stock Holley 750 VS has out performed my Holley 650DP, Holley750 DP, and a Demon 850DP.

I'm running a BG 750 race demon on my 406, its driven on the street, some strip and it runs great on the street and even better on the strip

If you're going to see the strip more often, I would go with the 750. But because it's a cruiser car, I would go with the 650 since it has mechanical secondaries.

Ultimately, I would not get a Mighty Demon, looking at the info that you have given. I'd go with a Speed Demon 750 with vacuum secondaries. If you had more stall and lower gears, I would recommend a mechanical secondary carb.

BG said to stay away from the speed demon line because my cam is too big dfor it, i'd say it is borderline.

What about a 750 vac secondary? That might work better with your OD transmission. The 650 DP would be fine too IMO.

That 650 Mighty Demon will run great on that motor. It should be responsive as hell (every mighty demon I've installed has been crisp and run strong basically outta the box). The 750 would work better on the strip, but in a driver car with an auto I'd stay small. The Speed Demon carbs DO NOT work properly on motors with cam 240* or bigger duration @ .050".

Originally posted by joesmith69:
The Speed Demon carbs DO NOT work properly on motors with cam 240* or bigger duration @ .050". Maybe in some cases but the 750 Speed Demon works awesome on my 383. My cam measures 252* @ .050 at the valve.

I say Barry Grant is right on with the 650. On my old 355 motor the 750VS ran pretty good. But when I tried a 650DP I could not beleive the difference. I know the DP had something to do with it but if its primarily a street machine I think the 650 will work better. It should help mid range torque were you will need it most with that 1-2 gear drop in the 700r4.

Another point too . . . I have heard that Demon carbs tend to flow in excess of the advertised cfm rating where Holleys tend to flow a little less than the advertised cfm rating. So maybe a 650 DP Demon is a pretty good choice when a Holley 650 DP might be a hair on the small side.

Eric, your right about the flow rates of the Demon vs. Holley. That 650 mighty demon will flow close to as much air as the Holley 750.

You're one of few who I've heard of having success with a Speed Demon and a large cam.

Let us not forget that a 650 Mighty Demon is WET FLOWED. It is much more than 650cfm probably more like 750cfm maybe more dry flowed. Holley Dry Flows there carbs, Barry Grant Wet Flows his. Theres a big difference. My neighbors 850 Mighty Demon annular booster that supposedly flows more around 950+ cfm dry flowed according to the tech he talked to at Barry Grant.

Thanks guys, too bad a 650 isnt any cheaper.

Originally posted by Eric68:
</font><blockquote>quote:</font><hr />Originally posted by joesmith69:
The Speed Demon carbs DO NOT work properly on motors with cam 240* or bigger duration @ .050". Maybe in some cases but the 750 Speed Demon works awesome on my 383. My cam measures 252* @ .050 at the valve. </font>[/QUOTE]ditto on that with mine, eric. its a 750 speed demon, and a .050 duration at the lobe of .250 . it runs killer around town, and seems to work well at the track as well. next year i am going to try my buddys 950 race demon at the track just for kicks, though. it has seen several different combos on the dyno, and seems to make more power everytime, plus you cant miss an oportunity to real world test different carbs.