Holley vs Demon

[Bill75]

I can't believe I'm writing this but I'm thinking of making a carb switch from the Q-jet to either a Holley or Demon, I'm getting a little tired of trying to get this Q-jet to perform better for me.

I've been searching thru a bunch of forums on this subject, it seems to boil down to the fact that both the Demon and Holley have to be set up correctly for the application (not a problem and fully understandable) and frequently people choose the wrong carburator for the application which leads to a mess. This seems to be more apparent with the Demon comments I've read.
Of the comments I've sifted thru, there's been quite a few on Demon quality control; metal chips inside, bowls leaking, misadjusted butterflies, etc. But not a whole lot about Holley quality issues, just getting them set up properly. About an equal number of satisfied customers on both sides of the fence, but the satisfied ones rarely comment on good things. You only see the bad things reported.

So for my ZZ4 engine w/Muncie and headers, Demon makes a carb designed for it. p/n 1282010VC ZZ4 a 650 w/ vacuum secondaies

Holley recommends a Street Avenger 0-80670 a 670 CFM w/ vacuum secondaries.

The Demon is around $500 while the Holley is under $400.

So the bottom line is............what do you guys think based on your experience with these things?
Is the difference in $$ worth it?
Is the Demon a good design and is it the right choice for this engine?
Would a properly dialed in Holley be equal or better than a Demon? There seems to be allot more information sources and experience with the Holley carbs.

I'm not into drilling holes in butterflies and remachining passageways. If I have to go down that road, either I've chosen the wrong carb or it's time to consider fuel injection!

As always, all comments are appreciated.

Thanks,

Bill

 

[Grizzly]

Put a road demon on my '67 300hp. Took it out of the box and hooked it up. Adjusted the idle and that's been the sum total of the problems for three years. Starts good. Will lug down to 500rpm in high and you just punch it and away it goes with no stumble. From the looks of the plugs could be a little rich, but I would rather have it that way.

Some day will have someone restore the old OE Holley, the car is good enough for it. Lord knows it needed it, floats stuck wide open and bowls leaked. Damn near toasted me one day. In the mean time I have no worries about carburation....................Griz

 

[GerryLP]

...I've been searching thru a bunch of forums on this subject, it seems to boil down to the fact that both the Demon and Holley have to be set up correctly for the application (not a problem and fully understandable) and frequently people choose the wrong carburator for the application which leads to a mess. This seems to be more apparent with the Demon comments I've read.

The Grant's Demon design takes the good features of the Holley, and it adds some more additional features. Unfortunately, the Race Demon is perhaps the better and more expensive option. The lower models are there just to bridge a market.

Having said that, you can stick with a good old Holley just as well and make enough adjustments to satisfy your fancy during weekend 1/4 mile passes (granted, albeit with slightly more manual labor involved). If you're seriously racing, then the Demon could be more useful. The one very useful feature is the ability to change venturi area, so in effect, you can have one carb with a large range of CFM's. The draw-back, it gets expensive unless you have a benefactor or sponsor.

GerryLP:cool

 

[AKRAY4PLAY]

well both carbs are very similar. the Demon is better because of machining and better castings. it also has removable boosters and the "idle ease" port for tuning cammed motors. i also like the removeable air bleeds and emulsion bleeds for all the circuits on the Demon. Holleys are bare bones carbs compared to Demon. the Holley you are looking at most likey has fixed air bleeds and emulsion ports. it's not a big deal, but if you need to tune it will be. you kinda hinted at future mods, if you change much from the set-up a Holley was spec'd for you will need to work the idle feed restrictors and low speed air bleeds for sure and maybe even the emulsion bleeds to recurve your fuel supply for a different powerband. if you plan on running a ZZ4 out of the box and never changing anything a Holley will work. if you plan on spraying it, cam swapping, etc. i would most definately buy a Demon. i ran a Holley on my 406 while dyno tuning and then swapped a Demon on and made more HP and TQ with the same set-up except the carb swap. can't remember the exact numbers off hand, but it was around 50 HP and 35 TQ more with the Demon. the idle ease system and flexibility in tuning with Demon carbs are well worth the extra cash in my book. you might also look into an O2 tuner like the LM-1 from Innovative Technologies after your motor swap, coolest tool in my box by far!
happy tuning, Brian.

 

[Bill75]

Griz, that's just what I want. Take it out of the box tighten down the bolts and go down the road! I hope I'm that lucky.

My motor has a cam duration of 208-221 deg I/E, from what I'm reading on the BG site the Race Demon is for engines over 260 deg so that might be a bit much for this thing. But I'm not sure that "Crate Engine" carb they make is enough for the occasional strip run either after reading a little more. Maybe I'll call them tomorrow.


Brian, 50 hp and 35 TQ is a super gain by just switching carbs and I'm betting the Holley you had was set up pretty good when you took it off. I have read a bunch of stuff about the LM-1, I'd love to have one. Better yet I wish my neighbor would buy one so I could walk over an borrow it! This stuff never ends !

I appreciate the detailed replies with good information. The way this project is going I can see myself doing a cam swap and heads next, so the Demon might be a good choice in the long run. I'll see what size their tech support recommends.

Bill

 

[Lucy64]

I just put a Holley Street Avenger 770 on my 64 a couple of months ago. I had a Edelbrock Performer 800 cfm carb on the car and could never get it right. The new Holley dropped right on and was pretty close right out of the box. After a few adjustments she is running really well. I looked at the Demon, but could not justify the extra $$. I am comfortable with the Holley and it performs great.

 

[Hib Halverson]

First, let me say that for a ZZ4 such as discussed in the first post, a properly modified and calibrated QuadraJet is the best choice. The QJ is a better street high-performance carburetor, once it's tuned right, than the Holley or the Demon.

If you set on taking the QuadraJet off, I'd go with the Holley. I've heard too much anecdotal information about Demons having problems with poor-quality--two cases of Demons being disassembled to find machining chips left inside the carbs and several cases of the carbs just not running right.

Again, the QuadraJet is a great choice for street-hi-po engines up to about 450 hp, but if you're going to make a change, go with Holley and one of about 650-700 cfm with vacuum secondaries.

 

[GTR1999]

Bill,
We're running a 750 speed demon on our 380-400 hp '75 ,just put a 670 st avenger on my '72, and have a lars built Q-jet that I ran on a couple of cars.

The Demon is run without a choke and is a PITA to setup.We've rejetted it several times, got it to run pretty good with straw colored plugs but it still backfires every once in a while.

The Avenger was only run during break in so I don't know yet how well it will perform,but I expect to go through it as well.

The Q-jets I ran on the 69 & 72 were great. Used them for years with the divorced choke setup. Once set they were set up, they were pretty much trouble free.

We bend up our own fuel lines like Lars outlines years ago also,stay way from running glass filters and rubber hose, unless you have full fire ins.

 

[74bigblock]

Not to go off topic here, but I have an Edlebrock 750 (1407 to be exact). Never had any trouble with it at all. There are only two adjustments you can really make other than setting the idle mixture: Meetering rods, and jet size.

 

[goingballistic]

Can't speak for the Holley but can for the Demon and Edelbrock.

I just got off a dyno test after a full rebuild. I had problems with the Edelbrock 750 CFM I ran and switched to a Demon. I do not have the car on the road yet so can't speak for the actual carb I have on the road. I do know that the first Demon carb they put on the engine after the problems with the Edelbrock did not function as advertised so I switched carbs to an 850 Demon to finalize my dyno run and stayed with it. It's oversized for my application but that's OK. I was not impressed with the quality of the Demon carb that they first put on, the carb that's there, the jury is still out. What I will share is that the air path down the throat of the carb is a lot less convoluted down the Demon than just about any other carb I have seen, opens and you can see right down into the manifold...........so what?????????? air swirl in the carb causes a loss in horse power. I was concerned about horse power which is why I rebuilt in the first place.

So I am impressed with the design but not the quality. If you compare the air path or the Demon, Edelbrock and Holly you'll see what I mean. I have not heard good things about Holleys which I why I started with the Edelbrock, leaks etc, not hard to set up but leaks galore, I am now not impressed with Edelbrock and as I said the jury is out on the Demon unitl I get the car on the road and drive it but am generally impressed with the horse power increase I got. I wish I could have done a side by side comparison to put this to bed but Dyno time is expensive

Paul.

 

[Bill75]

I called BG today spoke briefly with a tech guy who recommended a Crate Demon for the stock engine and a 650 Road Demon if I was going to put a cam and head upgrade later. Said the Road Demon would be perfect even with the engine the way it is. Not expecially a personable guy who didn't offer any other info other than a short answer to a question. I suppose the phone rings constantly with the same questions all day.

I've read the same or similar comments about the Quality Control on these things, guys finding metal chips in them after taking them apart. No excuse for that stuff for a precision piece of hardware and for that kind of $$$ too!

All your comments from about the Q-Jet are true, I think it's an excellent carb. I can take it apart and put it back together properly it's just that I can't correct a problem by making an adjustment because I have no clue what does what. Changing jets and metering rods is a cake job but knowing where exactly to look for something specific is where I'm lost. I understand also that ANY carb can give the same kinds of frustrations but this thing being 30 years old may have some worn or plugged gadget that wouldn't be that way in a new carb. (maybe!). I have nothing against the Q-jet and I'm not set on getting rid of it, just a little frustrated trying to make it "sing" right.

74BB thanks for the Edlebrock comments, I haden't considered that route but there's allot of folks runing them that are very happy.

I read on this forum I think, someone said if you combine all the carbs shipped to people it seems about 1 in 6 is a piece of junk that never should have left the factory regardless of who made it. Seems to be allot of Demon problems though.

I just finished changing the main jets again to a smaller size, haven't tried it yet. Maybe I'll get lucky and stumble on something.

Still appreciating all the comments.

Bill

 

[Bill75]

I do know that the first Demon carb they put on the engine after the problems with the Edelbrock did not function as advertised so I switched carbs to an 850 Demon to finalize my dyno run and stayed with it.

Paul,

I wonder if you had a chance to talk to BG about the problem and if they helped you or not? Was it a new carb?

Bill

 

[BarryK]

Changing jets and metering rods is a cake job but knowing where exactly to look for something specific is where I'm lost. I understand also that ANY carb can give the same kinds of frustrations but this thing being 30 years old may have some worn or plugged gadget that wouldn't be that way in a new carb. (maybe!). I have nothing against the Q-jet and I'm not set on getting rid of it, just a little frustrated trying to make it "sing" right.

Bill

I have a bunch of Q-Jet tech papers on my website tech articles page from Lars Grimsrud who is pretty much a Q-Jet guru.
You may wish to check them out and download them, espiecally one called "Q-Jet Problems.pdf"
they are here: http://69.253.166.197/page1/page65/page65.html

The Q-Jet is an excellent carb and i'l try to work with it a little more before giving up on it. Lars rebuilt the one on my '78 L82 and the thing works VERY well.


Barry

 

[Evolution1980]

Bill,

I tempted to say, "Just send me your QJet and I'll have my mechanic rebuild it spec-for-spec how mine is." I know that it sucks having a QJet and not being able to get it tuned correctly, especially when it's such a great carb to begin with (and recommended as such). But we all understand that feeling of "Look, I just want to be able to drive my car!!"

I think I may have mentioned it in our emails, but whatever carb you do settle on, you won't know for sure if it's running right until you get it on the dyno with a tailpipe sniffer to check your power curves and A/F ratio.

 

[Bill75]

Bill

I have a bunch of Q-Jet tech papers on my website tech articles page from Lars Grimsrud who is pretty much a Q-Jet guru.
You may wish to check them out and download them, espiecally one called "Q-Jet Problems.pdf"
they are here: http://69.253.166.197/page1/page65/page65.html
The Q-Jet is an excellent carb and i'l try to work with it a little more before giving up on it. Lars rebuilt the one on my '78 L82 and the thing works VERY well.
Barry

Hello Barry,

Hey thanks for the link to your site, lots of real good information there. Nice job!
I downloaded and printed a couple of papers to read. (not during work of course ).

Thanks,

Bill

 

[Bill75]

Bill,

I tempted to say, "Just send me your QJet and I'll have my mechanic rebuild it spec-for-spec how mine is." I know that it sucks having a QJet and not being able to get it tuned correctly, especially when it's such a great carb to begin with (and recommended as such). But we all understand that feeling of "Look, I just want to be able to drive my car!!" I think I may have mentioned it in our emails, but whatever carb you do settle on, you won't know for sure if it's running right until you get it on the dyno with a tailpipe sniffer to check your power curves and A/F ratio.

Thanks for the offer..........yeah with the driving season short as it is and all the darn rain we've been having, I'd hate to pull the carb now. Guess I could sit in the drivers seat with a beer and listen to the radio in the garage then!!

I did discover something interesting.....your carb jets were the same as mine .074 but mine runs rich and crappy. So I started changing the main jets only, last night I got down to a .071 and it runs strong, a very noticable improvement. BUT, down low at real light cruising throttle it's sluggish. Once the throttle is cracked a little she takes off. I also discovered the other day that screwing in the idle adjustments on one side will stall the motor like it should, the other side will not. It'll change and run a little rough but never stall out. Backing them both out 4-5 turns and the thing purrs like a kitten. You could literally put a glass of water on the air cleaner. So I'm thinking this thing is getting fuel from somewhere is not supposed to when that adjustment is seated. That might be the issue. The fact that I can run a .071 with good performance seems a little fishey to me but I'm still not too smart on this stuff.

Thanks

 

[Evolution1980]

I did discover something interesting.....your carb jets were the same as mine .074 but mine runs rich and crappy. So I started changing the main jets only, last night I got down to a .071 and it runs strong, a very noticable improvement. BUT, down low at real light cruising throttle it's sluggish. Once the throttle is cracked a little she takes off. I also discovered the other day that screwing in the idle adjustments on one side will stall the motor like it should, the other side will not....etc...

Let me run that by my mechanic as well as what you mentioned in your emails. He may have some ideas. He's pretty good about hearing of a problem and being able to diagnose it.

 

[AKRAY4PLAY]

Brian, 50 hp and 35 TQ is a super gain by just switching carbs and I'm betting the Holley you had was set up pretty good when you took it off. I have read a bunch of stuff about the LM-1, I'd love to have one. Better yet I wish my neighbor would buy one so I could walk over an borrow it! This stuff never ends !

Bill

Bill,
i spent three days on the dyno total. the first 2 1/2 were getting the Holley as good as it will get. the dyno shop had the Demon on a 440 small block and popped it on for ****s and giggles after maximizing the Holley. the difference was pretty amazing on the first pass, and even better after upping the main jets. throttle response was also crisper with the Demon. as for carbs coming with metal shavings from the factory, why aren't people fully inspecting their stuff before installing it?? ya it's bad quality control from any manufacturer, but it happens and it's still the end users responsibility to insure the parts are correct before install. after seeing the results, i am sold on Demons. they are more tricky to tune, as i stated in the earlier post, but not impossible. i am surprised the tech guy was short with you. when i called about getting my idle circuit leaned out, the guy kept me on line for 25 minutes longer than needed supplying extra tuning tips and info about different parts and throttle linkage cams. the tech dude definately went above and beyond helping me out.

 

[goingballistic]

Paul,

I wonder if you had a chance to talk to BG about the problem and if they helped you or not? Was it a new carb?

Bill

Bill, I was on a dyno and the guys running the dyno had swapped the carb. They had Demon on the phone and were complaining about the quaility as this was not the first time ( apparently) this had happened. They did however say that Demon was very responsive which is why they only deal with Demon,BG in the first place. I have called Demon and am so far impressed with their tech center guys, so to your point, yes they have been helpful for me and for the guys who own the dyno shop, so I decided to stay with Demon. As stated earlier, the jury is still out until I get the car on the road and see what kinds of tuning problems, if any, I have.

I think Arkplay said it best........."it's the user responsibility" to ensure the parts are right. I purchased AFR 195 heads ( expensive) and they say right in their docs....blow the heads out before installing, when machining parts they cannot ensure all the shavings are removed, it's your engine, your choice I guess.

Paul.

 

[Whiplash]

Bill, I was on a dyno and the guys running the dyno had swapped the carb. They had Demon on the phone and were complaining about the quaility as this was not the first time ( apparently) this had happened. They did however say that Demon was very responsive which is why they only deal with Demon,BG in the first place. I have called Demon and am so far impressed with their tech center guys, so to your point, yes they have been helpful for me and for the guys who own the dyno shop, so I decided to stay with Demon. As stated earlier, the jury is still out until I get the car on the road and see what kinds of tuning problems, if any, I have.

I think Arkplay said it best........."it's the user responsibility" to ensure the parts are right. I purchased AFR 195 heads ( expensive) and they say right in their docs....blow the heads out before installing, when machining parts they cannot ensure all the shavings are removed, it's your engine, your choice I guess.

Paul.

I just bought a Speed Demon 650 with mechanical secondaries for my new motor. The tech line was medium helpful but they came up with the recommended carb after a lot of questions.

Several people mention shavings in the carb. How do you inspect the carb for shavings before you install? Where exactly did they find the shavings?

Thanks,

Whiplash