Had a Mighty Demon 850. It was terrible! Customer Service sucked!

Installed a used 830DP. Ran better however still rich for my 482 Pond motor.

Now I have a BIGS Holley 750HP stage 5. Good carb. Cobra now starts right up. Would recommend BIGS or Pro Systems. Now real happy with the service I got from Quick Fuel I the past. They really don't stand behind their product.

I like my Demon RS 1050 but I'm also amazed at how well my big inch Clevor runs with an old Holley 900 cfm 3 BBl!

Steve

Speed Demon 850!
 

I have a Speed Demon 850 on my 427fe and it runs great!

It was not 'out of the box'.
It was 'tweeked' by Tom at FE Specialties when he installed it.

I'm very happy with my Demon.

It was part of the complete 66' 427fe side oiler engine package that dyno'ed at 603/635. Wow!
What more could you want from a 40 year old iron block?

jdog

I'm sure there are many manufacturers that make carbs that would work great if turned and set up per application, but in my opinion if you're not capable of setting up a carb to perfection yourself just call Pro-Systems and run better while going faster.

I have small block Roush 427R-095. My particular 427R came with a Victor Jr. single plane intake and AFR 205 heads. I have two carbs in the attic that I don't use, but I did fiddle with when I got my car. One is the Roush supplied Holley 750 double pumper. It worked pretty good up to about 6000 rpm. The other is a Holley Avenger 870 vacuum secondary. I could never get the vacuum secondary to work well regardless of what spring I used in the little canister off to the side. I'm sure both carbs are fine for whatever purpose if they're set up correctly per application, but definitely weren't what I was looking for. I called Patrick from Pro-Systems looking for more. I originally asked for a carb that would accelerate in a straight line as fast as possible. For the most part this is what I like. After some discussion of my engine design I ended up ordering a Pro-Series 4150. He asked my zip code so he could tune the carb for my location and season. I got the carb, bolted it on and it absolutely hammered exactly the way Patrick said it would. It's like a light switch for power if desired and smooth as silk under casual acceleration. I can even cruise at 1500 rpm if I want to too, usually cruise about 1800 though. carb pic Dynojet

I'm in a car club that rents road courses a couple times a year to fart around, so I ordered another carb from Pro-systems for that purpose. I've not put it on the car yet because the other one is so much fun already. It sure is pretty though. carb pic

I had a 750 Speed Demon that several of us tried to adjust properly. We could never make it idle well. It was all over the place. So, I replaced it with a Holley 670 Street Avenger that has so far (3K) work flawlessly. Perhaps the 750 was too much for my 351W with mild performance cam, but at idle? Anyway, the Holley is a very good carb.

SkipB

I have been very happy with my Mighty Demon 750 for the last 4 years. Ran great out of the box and since then only very minor tweaking for idle mixture, idle speed, and float settings. These carbs do adjust somewhat differently than a Holley so if folks are just assuming their old Holley adjustments will work they should read the documentation and start over. I have also heard about problems with the newer Demons on this forum but have no first hand knowledge of any issues. The Demon design and features are all very good for the money but if they are having quality issues it really does not matter. I know if I were buying a carb today I would be very careful to check if the Demon still has problems. Check a local speed shop and see if they have been getign customer complaints or returns.

Quick Fuel Technology 650 Road Race carb out of the box was xlnt on my 375/302.Hi quality workmanship, 4 corner adjustable, and less expensive than the Holley Race carb or any of the custom out of box race carbs. Best price at Jeg's

Dean