demon carb-->help<--

[NUTHIN]

ive got a 450hp sb chevy with a 725cfm demon on it. my buddy and i have TWEAKED on this thing for the last yr and a half. it idles great @ 800rpm. with the motor warm you stomp on it and it $hits on itself for a second then gets with it. so i got pissed and bought a new edl 750 and it idles great and the imeadiate response is way better then the demon but the top end sucks, so the demon is back on.. tweaked on the demon for a few hours.. same $hit.. F@#k this thing.. which holley to buy to match the demon? it sits on a airgap with a 1/2'' spacer.. thanks!!
anyone else have prob with these carbs?? damn..

[Itsahobby]

Did you try calling Barry Grant? The tech line has been very helpful in the past.
Jerry

[SmokinLowriderSS]

Yes, the above.
Is this only from an idle to WOT slam?
What happens if you just roll the throttle down slower? Does it do anything then?
Once you are above idle (cruising at part throttle), does it have any problems being slammed WOT then?
Sounds like a starvation just off idle to me, depending on the above answers, which is usually an accelerator pump problem.
On a Holley (don't have a demon so I don't know) the accelerator pump is not only adjustable by output size, but actuation timing and timing volume is adjustable by the plastic cam that drives it (shape & size). Also the accel pump shooter size is adjustable (which regulates fuel shot output volume as well).

[hellman2u]

The best advice I can give you is call Don @ 503 627 0728 or Email him @ www.4secondsflat.com. Go to his website and look around. He has written a book on tuning Demons and others. Buy his book for 10.00 it explains the whole event of whats going on and how to make them work. When you buy his book he will also assist you by phone. The guy knows his ***t. Good luck its not black magic. CDBA "HOWLER" 439 Jim

[Schiada76]

Throw it away and buy a Holly.

[NUTHIN]

im with u schiada.. nope at cruising speeds stomp it to the floor and it is GONE.. this motor is in a car. 62 nova, if i ease into the peddal it is fine!
at 65mph on the freeway wot it kiks down into 2nd and burns em off with 3.56 gears.. ive got dominators on all my boats and they are great! this demon is the most timid pos EVER.......! what holley to buy to match the flow of this demon? 750 dbl p ? the motor is 10.75-1 with comp 280 hr set up, old set of 462x f heads with a TON of work.. thanks!
im hanging this demon by a rope in the middle of my garage!
when cold the demon flows enough with no choke, it doesnt die, the edl had a hard time when cold..

[WannabeRacing]

IS the thing throwing black smoke when you stomp on it?
If it is, it will most likely need one of two things. Drop the float levels, as this will throw too much fuel right at the hit. Or check and see if your squirters are too much for your application. Or try to increase the lash between the arm and the squirter activator. If it is dying because of too lean, then try just the opposite. Raise the floats, set less lash less, and up squirter size. I cannot see a 725 BG out of the box with squirters small enough to run this car with perfection. So my guess is you have been through that and put smaller in.
But if you just want to toss it and get something else, then that may work too.

[NUTHIN]

car doesnt smoke at all.. it doesnt ever die, it seems like it pauses -flutters a sec then goes. weve gone threw the demon, floats/jets everything.. just time for a holley, which one would match the demon??

[Wicked Performance Boats]

Most peeps don't set the acc pump correctly. Have somebody push the acc pedal to the floor and hold it. Now check the acc pump lever to see if it has approx .030th play before it bottoms out. Just push down on it and see. If not adjust it till it does. Now is the flat spot still there? Budlight

[NUTHIN]

kinda went threw all that, also went threw dist, hell seems like weve been threw everything 10 times.. thought about diggin a hole in the backyard for it.. as long as that demons been on this motor the crows been hangin out at the house. thought about sending it back to BG with no return address

[SmokinLowriderSS]

Ok, just my opinion, and some will differ with me on parts of it.
You're dropping the throttle wide open and it pauses, lean, from insuffiucient accel pump fuel suply to fill the "hole" you just opened up in the airflow-comanded fuel supply, basically one of the signs that the carb is bigger than needed (there's where folk's will disagree). You have enough carb there to feed the engine at 100% VE, at 8,000RPM (realistic VE at probably 9,000), slam it wide open at 1/8 of that RPM and it's going to have trouble getting the main circut to START feeding. Once it does, you are fine.
Get the book, seek advice from Don and Barry as well (after getting the manual to learn more) and figure out how to adjust it properly to overcome this.

[Sleek-Jet]

BG is going to tell you you've got to much carb for the engine/rear-end combo. My brother has a health 350 in a Chevelle with 4.11's with a 750 cfm Speed-Demon... BG recommends at least 4.56's if you want to run a 750... we've had a time getting it tuned, but once we did, it runs like a raped ape.

[Wicked Performance Boats]

I'm told by the carb shops to shitcan the demon and stick with Holley! So take the holley and have it setup for your application. They say Demons are junk! Now all you demon lovers don't get butthurt. I'm a holley guy myself. Budlight :argue:

[Sleek-Jet]

I'm told by the carb shops to shitcan the demon and stick with Holley! So take the holley and have it setup for your application. They say Demons are junk! Now all you demon lovers don't get butthurt. I'm a holley guy myself. Budlight :argue:
Why do they say that??? Essentially they are a Holley decendant... personally I like the E-brock performer's myself.

[NUTHIN]

that may be the case, too big of a carb.. i see maybe 6200 with the gear combo ive got, the car weighs 2650lbs, the motor is PLENTY for the car. i went with the biggest stick that i could, still keep it streetable, without going over 11.1 comp. i thought about changing to 3.90 gears, easier to change the carb. the weight issue is why i didnt change to the gear, as it is with the 356 gears it wants to break free no matter what..

[MikeF]

But, It's the coolest looking carb on the market! :skull:

[NUTHIN]

totally agree!

[motormonkey]

I have had more bad than good street demons. The customers seem to like the looks over holleys.Ive found junk from the factory in the metering blocks from machining. The race demons are good. It sounds like tuning problems though.

[Wicked Performance Boats]

Why do they say that??? Essentially they are a Holley decendant... personally I like the E-brock performer's myself.
Demons are made from most of the same design But are completely different castings. The quaility is not there. Maybe the race demons have more mechining steps for quaility control. BL

[NUTHIN]

which one i have,725 speed or race.. think it was 4-$500 bucks.. i had a 650 demon on my less built 327 in a 63nova, way smaller cam cmv272, and the demon was FINE... this ones been off the motor twice, tore down checked rechecked, jets changed 4-5 times, nice to hear others have issues with them also..

[Terminal Velocity]

I had a friend who bought one and was having the same problems you are. What we found was that the motor needed 35 squirters, and an 8.5 PV.
What is your manifold vaccum at idle and at cruising 45-50 mph?
What we also found is that if we opened up the idle screws so that it was WAY rich the stomp and stall would start to disappear this is where we started going up on the squirters. Granted we only went from the 33's supplied to 35's. The power valve was selected because at idle (adjusting the idle screws to achieve maximum vaccum) I could get between 10-11. I tried a 9.5 and it was too much, as soon as i put the 8.5 with the 35 squirters, readjusted the idle mixture screws ALL hesitations stopped.
The circuits go as follows:
Idle screws - well they meter the amount of fuel at idle.
Squirters - When you stomp the loud pedal from idle or at cruise they make up for the sudden large amount of air.
Power Valve - When you open the throttle quick vaccum drops this opens the valve and richens the midrange circuit under acceleration until vaccum again rises.
Jets - Although they do work somewhat throughout the RPM range, they are mainly for the top end metering of fuel only.
In my opinion jets aren't going to do crap until you get the right squirter and power valve for your combination.
Try richening the idle screws 4 corner could be 2-2.5 out (basically to the point that you cannot stand to be in the garage because of the fumes) if the stumble begins to go away they you need to up your squirters.
One other thing have you messed with the secondary idle screw?

[NUTHIN]

is running fat, fumes arent to bad tho.. vaccum is at 14..

[Terminal Velocity]

is running fat, fumes arent to bad tho.. vaccum is at 14..
is it running fat due to upping the jets? or because you've backed out the idle screws? What jets do you have in it now?
If your running 14 vaccum at idle you're going to need in the neighborhood of a 11.5 PV to richen the circuit. I'm guessing you have the standard 6.5.
What squirters do you have?
My guess/recommendation would be 35 squirters, 11.5 PV, 1 to 1.5 turns on the idle mixture screws and 70primary-74secondary(to start) jets.

[NUTHIN]

for sure on all the questions. thinking the jets are 73 77 or close to that, going to tune at the dyno for last effort, buddy is going to go in halves for the day, then i suppose there will be no guess work! but im going there with a new holley 650 also,, hopefully we will come across something that youve been explaining, but if not carb is coming off!!!!! motor put some gd hp. to the rear wheels last time we were there!!

[Terminal Velocity]

for sure on all the questions. thinking the jets are 73 77 or close to that, going to tune at the dyno for last effort, buddy is going to go in halves for the day, then i suppose there will be no guess work! but im going there with a new holley 650 also,, hopefully we will come across something that youve been explaining, but if not carb is coming off!!!!! motor put some gd hp. to the rear wheels last time we were there!!
That's cool. I'm sure you'll get it figured out, these items i've discussed are what i've learned from John Avery who builds my carbs for my Super Stock and when i helped my buddy with his demon i called their hotline and they told me it's the same thing. The people i know who are really into the demons say that they are a little more exacting to get right but when you do get'em there they will run better in a multitude of eviroments. The holley's seem to be more prone to weather and altitude changes than the demons.
Good luck hope it works out for you. I'll be checking back to see what you found out and tried.
James
PS if you want you can give me a call, 702-266-7322 i'll be at the drags all weekend so i won't be checking back here until monday.

[NUTHIN]

thanks alot james! greatly appreciated! ive heard the same thing, thats why i bought that carb! it is just timid to say the least..

[tbanzer]

It sounds like you need a bigger pump shot to cover up the time for the mains to take over. I would go up 2-3 sizes on the pump nozzels.