Demon v. Holley

Chaplin · #1 (**permalink**) 09-30-2003, 03:43 PM

I keep hearing how much better Demon carbs are than Holleys? Any truth to this rumor, if so why? What's the difference between them?

Any insight is appreciated

Mr.Fixit · #2 (**permalink**) 09-30-2003, 04:43 PM

I like Holleys better.

aumoore · #3 (**permalink**) 09-30-2003, 05:08 PM

The Holley is a tried and proven design and the Demon is supposed to be a better built Holley but I have heard that some of the Demons had problems.

The demon is pretty though.

Tongue Pirate · #4 (**permalink**) 09-30-2003, 05:24 PM

Chaplin, I had a Speed Demon on my 59' Caddy. It was a great carb! It is true that it is better designed Holley. The only real problem I had with it was with the vacuum secondaries & that was due to the fact that the carb was too big for my application. I convinced a buddy to run a Road Demon on his 69' Camaro. He has been running it for about a year & a half now without a problem & he swears by it! The only reason I will be running a Holley on my Cobra is that I want it to look a little more period correct. I love both brands but would choose Demon or a modded Holley if all out performance was my goal.

Samurai · #5 (**permalink**) 09-30-2003, 06:07 PM

IMHO

When I last dyno'ed my car at Westech, we ran it back to back with a Holley and a Demon. They both had 750 vacume secondaries. Both carbs while running on the dyno were tuned by the techs at Westech for maximum performance.

In my case, the Demon showed a healthy increase in TQ across the board. Torque was up as much as 20 ft-lbs. on the low end with the gap shrinking as the rpm increased over the Holley.

Needless to say I run a Demon now.

On a side note, I lose about 25hp using a oval air filter which totally neglects any performance benefit I get from the Demon. Again we ran with and w/o back to back runs. I need a better air filter....

Samurai

George Snyder · #6 (**permalink**) 09-30-2003, 09:07 PM

Chaplin,
I recently changed from a 650 DP Holley to a 65o Speed Demon. I now am using Speed Demons on both of my performance cars.

The Demon IMHO is jsut a better designed, better performing carb. It has features that simplify adjusting it at installation and for future changes. I feel for the money there isn't a better out of the box brand carb available. They are just hard to beat!
It comes equipped with the following features. Larger float bowls, glass site glasses for a esiler and more accurate setting of the float levels, individual outlets for both ported and manifold vacuum, a rear idle set screw fully adjustable with the carb on the engine vs. removal required on a Holley.
If you are leaning more toward performance than economy, try the mechanical secondary model. That is what I use and really like how they perform.
As a note, if you are presently using a DP Holley and want to reuse your present fuel line, Holley makes adaptors for about $8.
Bud

Samurai,
I also have a Cobra Oval Air Cleaner for my engine. It is very restrictive and I only use it for show. I normally rely on the 11 inch K&N X Stream assembly which flows approximately 698 cfms.

gene giambona · #7 (**permalink**) 09-30-2003, 11:01 PM

I purchased a pair of 725 cfm road demon Jrs for my 427 stroker tunnel port. The motor is still being built so I can't comment on how well they work just yet. I picked the demons over the Holleys because I wasn't going for that 100% authentic look and I wanted something new right out of the box that would work with my application.

I haven't met anyone yet at a car show that ever regreted buying one..... a majority of them bought the Demons to replace a Holley!

750hp · #8 (**permalink**) 10-01-2003, 05:38 AM

A pair of 725s? Wow, that's a LOT of carb for a street engine!!!

Samurai - thanks for the dyno info. Actual test results between the carbs is hard to come by. Did you try to optimise both carbs, or just try them out of the box? If you optimised them, how close were the jet sizes from one to the other?

Mr.Fixit · #9 (**permalink**) 10-01-2003, 08:28 AM

As contrast to some of the experiences here with demons, I have replaced a few BG carbs with holleys. They just ouldn't work right, didn't seem to matter what I did, what the owner did, just didn't make much of a difference. Right now, my friend Tim is running my holley on his motor and his BG is sitting in a box in his garage. It is a pre-demon BG version of a holley, for sale I think. I wouldn't buy it.

Cracker · #10 (**permalink**) 10-01-2003, 08:55 AM

I replaced the Holley on my side-oiler with a Mighty demon 825 and would not forsee ever switching back.

Chaplin · #11 (**permalink**) 10-01-2003, 09:23 AM

Cracker-
Why? What problems were you having with the Holley that made you swtich? What improvements did you notice with the demon? Inquiring minds want to know.

Cracker · #12 (**permalink**) 10-01-2003, 09:30 AM

Chaplin,

I've got to run to a lunch appointment but will respond when I get back.

Roscoe · #13 (**permalink**) 10-01-2003, 11:21 AM

Chaplin,

I've got a 650 speed demon on my 351W. I've been on the road for over three years and I really think it is a good carb. I have mechanical secondaries, not vacuum, and no choke. The car runs fine and I have no complaints. They have good tech support also and they helped me to maximize the carb when I was doing the dyno thing last year.

If I was going to do alot of racing I would consider either an upgraded BG or AED or DaVinci. Holley, to me, is just a standard unworked carb.

http://www.aedperformance.com/
http://www.davincicarb.com/index1.htm

Roscoe

Tony Radford · #14 (**permalink**) 10-01-2003, 11:31 AM

Tony, so you did it! Now for Mr. Crace, Chill and Randy. We can rename the local chapter to "Demon Derelicts".

Cracker · #15 (**permalink**) 10-01-2003, 01:35 PM

Chaplin,

First of all I had been running the original 66 780 cfm Holley carb that came on the 427's, so it was hard to depart from what "they" used. When I was having my engine rebuilt and built with a little more bite than original, the Holley as-it-was did not suffice both for flow and tunability (I make words up now and then). The quality (percieved) of the BG unit with it's billet metering blocks and base along with it's ability to be massaged more purposefully clearly outwieghed any benefits that my or any off the shelf Holley was going to provide. Four corner idle adjustment, site bowls you can actually see through (what a concept). Excellent tech support not that I had to use it too much but they were great at dealing with me BOTH before my purchase and after more importantly. I could have gone just about any route but in the end the BG products offered me the closest carb off the shelf to my application along with a super high quality unit. I haven't heard any bad reviews from anybody until Mr. Fixit today. With that said I run a race carb with mechanical sec. and no choke and have experienced no problems, yet.

To bring my old Holley up to speed I would have easily spent more than what I have in this one, however, last time I checked my "old" holley is still worth twice that of the BG - go figure. Best wishes! I'm not selling the 780 Holley but I do have an orginal GT350 Holley for sale if anyone is interested. Had to get that in there.

Tony Radford - We haven't convinced GeorgiaSnake to convert (to Demons

) yet but he's still on my prayer list but after reading the Willis 04 thread - I think I need to pray harder!

Chaplin · #16 (**permalink**) 10-01-2003, 01:40 PM

Cracker-
Thanks for info. I appreciate it. I'm going to give my Holley a little tweaking and ride it for a while and if I'm happy with it, I'll keep it. But if not, a demon may be on the way

Jack21 · #17 (**permalink**) 10-01-2003, 06:32 PM

Have always had love/hate things with Holleys. My first was on a '57 Fairlane with the "Big" 312 motor. Had this nasty habit of sticking in the open position at WOT, and wouldn't come back without shutting off the engine.

Holley did have the answer to Rochester Quadra-Jets that wouldn't run, but seemed like I was always tinkering with something on a Holley. Must have a sizeable investment in spare parts.

Same deal with the Cobra. Nice healthy 351W, but tinker, and tinker with the jets, power valve, idle, secondary throttle stop. 700DP (#4778).

Reading an engine buildup article in one of the rags. They decided to dyno the motor with a Demon, instead of Holley. Been seeing a lot of that lately.

Talked to Demon tech about selecting one, and the guy asks me what cam duration in my motor. I've never been asked that before, nor have I seen any references to this in Holley tech info. Demon tech guy advises not to use the Road Demon, it's calibrated for cams under 220*. Use the Speed Demon instead with the cam I'm using. Sooo, the Demons internal calibrations are more closely tailored to the rest of the engines components. Hmmm.

Sprung for the 650 DP Speed Demon. Could not believe the difference in this motor's smoothness, and responsiveness right out of the box. Like the Holley, it runs too rich out of the box because of the high vacuum hydraulic roller cams pull (15" - 16" at 850 RPM idle), but the 4 corner idle system sets right up, and no further tinkering required. So that makes me a believer.

The metering block is where the biggest difference is, and it's obvious comparing the two (Demon - Holley), that the Demon is more judiciously calibrated. It shows in the throttle bodies as well. Holleys have been around since the mid-'50's and the carb you took out of the box then is nearly identical to the one you take out of the box today. In some ways this may be good, and in others, it may not be. MHO, the Demon is worth the extra $100 - $150 over the Holley.

Also using the same K&N air filter as shown above. They're ugly, but they breathe.