Hello-
I need some opinions on which carb to select. Here are the facts:
Brand new 383, AFR 195's w/68 cc, Comp Cams XE274H flat tappet cam, Hooker Super Comps, edelbrock RPM Airgap, 5 speed Tremec TKO manual transmission. The car is a weekend fun car (not a daily driver), it needs to be streetable but I want the upper end uf street performance for weekend speed. I do not plan to race it.
I am going to go with a Demon carb so my question is - which Demon carb is best for this set up? I am considering the following models:
Speed Demon 750 (mechanical secondaries)
Speed Demon 650 (mechanical secondaries)
Mighty Demon 650 (mechanical secondaries)

I called Barry Grant Tech two times and the first guy recommended the Speed Demon 750. The second time I called a different guy said the Speed Demon 650 or the Mighty Demon 650 would be best?

Which one should I choose?

Thanks.

Jeff

I would go with the Speed Demon 750 myself. The Mighty is labeled for cams running over 250 @ .050 duration.

That aside, go with the 750 for sure.

Jeff

I have a 385 with a Cam Motion hyd flat tappet with 240 at .050. Pro Topline iron lightning heads 200 cc / 64 cc and an RPM Air Gap and th350 trans. I run a Speed Demon 650 mechanical with stock jetting. Great throttle response and idle . My car is street driven 98% of the time with occasional trips to the track. Could I run a bigger carb? Maybe. But the 650 works great!

David smile.gif

I called Barry Grant Tech two times and the first guy recommended the Speed Demon 750. The second time I called a different guy said the Speed Demon 650 or the Mighty Demon 650 would be best?
I think thats why most of us choose Holley, BG tech support leaves something to be desired. graemlins/thumbsup.gif

They used to be tough to tune,but it seems like they are getting better about that... more like Holley :D

I'm Running a comp 284 and have a road deamon 725 and it seems real nice and has great throttle response...

I ran the 650 on mine and this car would fly!mech 2nd's also.

I would run a 750 for sure if I were you with AFR 195cc heads! Mechanical secondaries are good for a stick also.

I ran the 650 on mine and this car would fly!mech 2nd's also.

650 mighty demon cc 280h 230@50, change pv and jetting and youll be happy
shane

please dont get caught up in "bigger is better"
shane

Jeff,

I'm not expert and have a long way to go, but I agree with the idea of bigger is not always better. Tom Mobley helped me answer several questions on this, when I was building my first 383. The basic equation for this is:

383 / 2 / 1728 * 6000 = 665 CFM.

383 = Cubic inches of your motor.
2 = Must divide it by two as only four cyln pull air on each Revolution.
1728 = changes the Cubic inches to cubic feet.
6000 = Equals the RPM you want to run up to.

Ignoring all the losses, effec, etc. If you plan on going up to or above 6K, you may want to consider the 750 CFM with mech operated secondaries. If you plan on staying below 6K, the 650's suggested should work just fine.
I put a Holley 750 CFM with Vac seconds, on the last 383 I built, and it seems to be running fine.

Fred.

Thanks everyone for all the input.
Jeff

Thanks everyone for all the great input.