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Mighty Demon or Holley HP??? Which is better?

32K views 71 replies 26 participants last post by  Scott C 
#1 ·
Which carb should I go with. Heres my engine combo:

SBC 383 9.81 compression
Dart 200 cc Iron eagles
Comp Cam x-treme energy 268
Performer RPM Air gap
MSD dist, and digital 6 plus box.
Sportsman fogger 150 shot
turbo 350 trans with 3000 stall converter
9 inch rear with 3.90 locker
26" tall tire in a 64 nova.

I was thinking a 750 cfm carb should work well but can't decide on a Mighty Demon or Holley HP carb. Or is there a better choice all together? Should i stay with mechanical secondaires or switch to vac.
 
#2 ·
I bought a couple of MD's recently, they work fantastic and do what they're supposed to but........machine work leaves a lot to be desired :(
If i had my $1700 to spend over again, i'd wait till i had more and go Holley. I've had lots of Holleys over the years and had no real prob's, buy a couple of BG's for the first time.......disaster :(

Maybe next year.

cheers and good luck with your choice.
jim
 
#3 ·
Let me start by saying that this is my opinion and in no way am I a carb expert (you will not find my name on any carb). I have a 750 Mighty Demon on my car now and it does a great job. I will agree with rodents statement about the machine work leaving a lot to be desired. Saying that I also believe when you buy a new carb ( holley or demon) you should disassemble it and check all orfices before installing.

I dont think you can go wrong either way ( holley or demon). I like mech. secondaries myself. One other bit of advice make sure what ever you buy that it is adjustable (screw in airbleed, screw in idle feed restrictors). That way you can set it up for your current motor and any future engine combo's.
 
#4 · (Edited)
Let me tell you my experience with BG/Demon Carbs.

First off my engine combo:

468 w/10:6/1 compression
Brodix BB2 Plus heads 245/ with 119 cc chambers
Brodix HV2000 Single plane intake
Comp Cams solid roller 262@ 50 with .652 lift

Ok that said. When I finished my engine I looked at all the demons and the applications listed for them. I went ahead and bought an 850 speed demon.

Problems:
On startup, the carb flooded like crazy. I'm not talking a little rich, I'm talking about eye watering flooding. I checked my fuel pressure, adjusted idle mixture screws and idle eze plate. It still flooded.

Called demon tech support before I did anything else.
Tech support guy A said that an 850 speed demon was WAY to much for my combo and said it was for engines with 500+ cubes and told me I needed a 750 mighty demon.

Fair enough. I bought a mighty demon 750. Put it on and the car ran fine.
However, when I ran against a buddy of mine with nearly the same setup only he had cast iron heads and a dominator he beat me by a full second. Yep thats right. I ran a 10.0 and he ran a 9.0 and thats 1000' friends. I'm not saying it is all the carbs fault because I have **** headers with 1 3/4 primaries and 2" exhaust which is soon to change. Still yet, with my engine setup in a 71 nova with t-350 3000 converter (which isn't quite enough) and 4.11 gears I should be ripping off the 1000' at a low 9 to high 8 without an issue. But nope. 10.0 @ 104 mph with a 1.6 60'.

OK Problem 2.

Sold the 850 to a buddy of mine from the track.
Flooded his engine too.

Get this.............
He pulled the bowls off and their was metal shavings all inside the bowls.
Not to mention that whoever tapped the main body for the baseplate screws went to deep and drilled a hole into the powervalve orifice.

I call BG and they give me an RA to send it back.

They look at it, clean it up and say there are NO PROBLEMS!? And that the hole will not hurt anything.

They send it back to me and I have to give my friend his money back.

I call support again and get guy B.

Guy B tells me that guy A is crazy and a 750 isn't nearly enough carb for my application.

I decide to try to run the 850 again to see if it is still flooding.

Guess what? It runs perfectly now even though they said no problems found.

Runs alot better than the 750 thats for sure.

So I sell the 750 and now I'm debating putting on a 1000 Race Demon or a Dominator this winter.


Overall, when the demons aren't full of metal shavings and **** they are great.

But like the others said the machine work isn't that great.

Don't make my mistake. Pull the bowls off and check for anything unusual prior to startup.
 
#5 ·
I've also heard that BG's quality control isn't great. I think that may be why Summit no longer sells BG carburetors. But, I've also seen tests with dyno runs and apparently, BG carburetors will put out more HP if tuned properly. I have a 750 Speed Demon on my Mach 1 and it runs fine, but when I tried to adjust the floats, fuel spilled out of the adjusting screws. I'm guessing BG buggered the o-rings on assembly. No big deal. My Nova is getting a Holley HP 1000, only because I got a great deal on it.
 
#6 ·
I have the real scoop why Summit no longer sells BG carbs. Summit would sell you a 1000 King Demon, regardless if your setup really called for a 650 Mighty Demon. Lots of unsatisfied customers, and as a result, the carbs were then sent back to BG, when there was nothing wrong with the carbs in the first place. BG told Summit to kiss off and pulled his carbs out of there.
 
#7 ·
Another vote for the mighty demon! I run on one my 383 and it performs great. Just make sure you get the 650 mighty demon. I originally started out with a 750 speed demon and it was just too much carb. They guy at demon explained that the 650 flows a bit over 750 and the 750 flows over 850. Why are they rated this way you ask...i have no idea:confused:
 
#9 ·
Funny you mention that. BG Tech support told me a 750 mighty wet flows 930 cfm.

Sounds like they pull a number out of their rear. Anyway, if that was the case then why not rate it a 930 mighty demon?
 
#12 ·
I don't have any experience with B/G so I can't comment yea or ney. I have read about similar problems on other boards. I just picked up a Proform 750 DP from racingjunk dot com that is a work of art. Will it run better than a Holley 750 DP set up the same...? Dunno.
 
#15 ·
Well, I have a Race Demon RS(w/sleeves from 775-975cfm) 1050 Dominator, and a 750 Street HP Holley. Of all of these, the Street HP impressed me the most--bolted it to the junk 350 and it works great right out of the box. I feel just the opposite concerning the Demon quality; the machine work on mine is far better than what I see on the average Holley piece, BUT, it took a long time changing sleeves, boosters, air-bleeds, etc., before it would run as fast as an 850 DP Holley. From my experience I tell people you're almost guaranteed to lose 20 H.P. bolting on a Demon over the same cfm Holley. All the magazine guys use Demon stuff these days because B.G. will kick out free stuff by the boatload. The magazines won't do A-B testing against each other so you don't make one look bad. Keep an eye on MaxChevy.com, they are going to do some testing that will show what works and what doesn't without regard to making the other guy look bad. I tried to get Hot Rod or Car Craft or Chevy High to do it, but you can't bite the hand that feeds you!
I was talking to a well known local carb guru the other day and he has a couple Demons sitting on the shelf that he couldn't get to run right no matter how he tried-he gave up and replaced them with Holley's. I told him he could give them to me but............
 
G
#16 ·
First off, I used to work at Holley, on Pro-Stock Dominators. And, IF the Demon were a better carb, I'd recommend it as vehimently as I now post against it, for the carb it really isn't.

I have seen way, way too many posts like the ones MuscleDreams has posted here, way too many to ever want to have to re-engineer a Demon of any kind just to get it to work. I have had to re-engineer a few of them, and I really don't need that hassle from a highly touted "should be workable right out of the box, as advertized" carb.

I have also heard and seen as many stories/posts about BG tech advice and phone personnel NOT helping with workable answers/fixes. There is even one of their "tech" people going around to various web sites, only to do nothing more than full on damage control from all the negative experiences posts, and he is not helpful either.

If you wish to become a knowledgeable carb tuner, three things, buy any Demon, buy also EVERY jet, part, changeover you can from Grant, you'll need them, then, make friends with a good Holley person, as they will have the knowledge to get the Demon working reasonably well, but it will never be the carb a Holley is right now.

Sorry to sound so negative, but truth is, it takes a major redo to get a Demon even close, and I have done a few for friends that were just frustrated all the way with both the carb(s) and the techs at BG. They are all back on Holley or have gone to a nicely done Q-jet over the Grant stuff, all of them.
 
#17 ·
Holley HP 750 gets my vote. and those sales techs that tell you its too big... They obviously dont know how the carb they are selling works. You could put a 2000 cfm carb on it and its only going to draw as much fuel as air that the engine sucks in. And 750 carbs that out flow 850s? Obviously one isnt what it claims to be.
 
#22 ·
Holley.

Too many probs with the BG products in general. I sold their product at a speed shop. I didn't like how customers were forced to buy their dual feed inlet systems for a while. We also had a problem where the air cleaners would not work (the AC base would get caught on the choke linkage) on the street carbs. I wanted to buy an entire BG system about 1.5 yrs ago. I could not get an answer if they were continuous duty systems or not. I called tech a couple of times but they were not sure. I asked the reps at a national NHRA event but the tech rep said "woa..you already know more than me so no sense in continuing". ..he was right. No sense in continuing. I bought another brand system and am very happy with it and my HP dominator.
 
#27 ·
I had metal shaving all throughout my Barry Grant Demon 750 dp. It ran horribly until I disassembled it to get out all the metal flecks and unmachined shavings still hanging in the bowls.:eek: IT runs good now but definately pull it apart. I was not impressed to say the least. Maybe they are different now b/c mine was probably 5-6 yrs old but still in the box.

just my 2 cents.
 
#31 ·
David D

Hey David D, what size carb are you interested in ??
I have a holley 4150 hp 830 cfm thats just over a year old, i want to step down to the 750 hp, but don't want to shelf the 830. pm if interested.
 
#32 ·
I have a Holley 950 HP on my 383. We started with an 850 HP and it was too small. Right out of the box the 950 jumped 39 horsepower. After DYNO TUNING, my horsepower went up by 29. My advise, see if you can borrow a couple of different size carbs. Go to a Dyno with someone who really knows how to understand what the dyno numbers mean and KNOWS how to tune it. My builder amazed the dyno operator, who is also a professional builder himself, by the corrections made and the power increases. But, my builder also has 40+ if not 50+ years of experience building race cars.
 
G
#33 ·
I'll just add this a bout flow ratges, the flow bench has holes for a number of corks to be removed/inserted, to change the air drag drawn through the carb. It is called "changing the depression pressure".

Add/remove a couple of corks, change the depression pressure, and a 750 carb instantly flows 950.
 
#41 ·
re

I have a 750 mighty demon on my Nova. I compared it to my old 800 holley DP i had on it before and it picked up alot. Now that said there are pro's and cons of both carbs.

The demon comes with billet everything where the HP holleys still have the weak pot metal baseplate that can snap. To get the "same carb" from holley i believe off the top of my head you have to spend in the range of $950. The second you get you demon you should pull it apart and clean out EVERYTHING. I couldnt get mine to idle right for ever and i was on my last nerve with it. I pulled it apart for the 3rd time and found a chunk of metal in my low speed air bleed that id never cought before. It fixed the whole idle problem. Now If you do buy a demon you have the be illing to tune. Its not a bolt on and go carb. WHen you buy it, get a set of idle feed restrictor blanks and air bleed blanks, find a place that can get you some small drill bits and get ready to tune.

I must say Barry Grants tech support sucks huge ***. All i got out of them after a 1/2 hour conversation was "sir we do not recommend that carb for your application. You need to sell it and buy our 650 race demon." I asked "why?" and he said because its more calibarated for your cam. I said well i dont have a fricken dyno to **** around with changeable emulsion circuits and he said "sir we do not recommend your carb for your application." They had no reason. At that point i hung up and never called back. Tech support is terrible.

All this said the carbs look great and run great once you get them tuned. they are half the price of the comparable "ultra HP holley" and im willing to tune. Im sure the holleys are a great piece but i dont like the idea of spending 650 bucks for a pot metal baseplate.
 
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