[east_texas_mach1]

I am looking for a new carb for the stroker I am building and have decided for the street Demon, but not sure what CFM range to go for. I have a holly 650 on the warmed over 351w and it ran good but this engine is different. Demons are 625 cfm, which is lower, or 725 cfm, which is more. I am leaning toward the 725, what do you think? A few other notes is my stroker is a 351w stroked to 393, Trick Flow twisted wedge heads, roller lifters and rockers, performer rpm, electronic dizzy and AOD. The mustang will see mostly street use but occasionally will be at the track. Thanks for any input.

 

[68COUPE]

I can't help you, but I will be watching this thread.

My father-in-law is running a 750 DP on his 347 stroker (66 Fairlane). Everything I have read tells me that it is too much. The car has yet to see any road time, but I am interested in seeing how it plays out. I may have to wait untill next year.

 

[dodgestang]

I have a 770 Avenger carb on my 410 cleveland with an AOD. My FIL says it is showing the tell tale tail pipe signs of running rich. I am going to the dyno on Friday so it may or may not end up getting soem jet work

 

[sharkmouth]

If that 393 has a cam with at least 230 degrees net intake duration and the car has at least 3.7 gears, I might consider the 725....

Otherwise, I'd probably use the 625.

 

[east_texas_mach1]

I plan to run 350 gears and the specs on the cam are as follows. Crane cam #449761
Degrees Duration @ .050 Int./Exh. 232 244
Degrees Advertised Duration Int./Exh. 294 306
Degree Lobe Separation 112
Gross Lift Int./Exh. .563 .595
So I think that I am close. What do you think?
Thanks all
Troy

 

[66stangFb]

I ran a 625 Demon on my 302, I was not happy with it and when I called them I was told by the Tech Support that I had too much cam for the 625 Road Demon. I'd suggest you call them and see what they think will work best for you. Contact info follows:

Barry Grant Incorporated
1450 McDonald Road
Dahlonega, Georgia 30533
[email protected]
Phone: (706) 864-8544
Fax: (706) 864-2206

 

[dailydriver]

The mustang will see mostly street use but occasionally will be at the track.

Bigger is not always better. The smaller the carb, the more streetable it will be. For the track, your engine will still only need a given CFM at maximum desired RPM.

The following site explains Carb Sizing well enough that you can easily determine the proper size for your needs.

Hope this helps!

 

[66benchcoupe]

Don't they still make the 650 and 750 Speed Demons?

I'd recommend looking into the Mighty Demon. A 750 should do nicely on your stroker.

Here's some reading on carb sizing:
http://www.carcraft.com/techarticles/56919/

 

[east_texas_mach1]

Thanks for all the response. 66stangFb I will give them a call and see what they say.
dailydriver I check the site out and their formula puts me in the 702 cfm range, based on 393ci, 6500 rpm and 95% ve or 665 cfm at 90% ve, still above the 625 road demon.
66benchcoupe yes they still make the 650 and 750 speed demons. The mighty demons I think would be too much for what I am going to use it for. I thought about the speed demons but was leaning toward the road demon. Car craft link came out to 739 cfm by the way. Is there any difference beween the speed and road demon? Again thanks all.

 

[BernieFrank]

I'm using a 750 Holley on the 347 in the Fastback (4:11 rear). The car runs 111 mph in the 1/4 on street tires and is not set up for drag racing. The throttle response on the street is immediate. I suppose the 750 is considered too big, but I'm more than happy.

 

[66benchcoupe]

Speed Demons are more 'race' oriented than the Road Demon. You can check 'em out on the BG site. I suggested the Mighty Demon for the tunability it offers. The Mighty, Race, and King Demons have tunable air bleeds, unlike the Road and Speed Demons. The rich idle problems I've had and others here have had could've easily been remedied with tunable air bleeds. That's why my next carb will most likely be a Mighty Demon. Here's an air bleed tuning article:
http://www.carcraft.com/techarticles/81958/