Demon troubles!!!!

[tweet66]

Yeah my carb's possesed I bought a 525 street Demon last year that I ran for alomost 3 months on my basically stock 302 in my 69 Falcon wagon and took off due to float flooding problems. BG customer service SUCKED helping with my problem (told me to rebuild a new carb) So after dumping some extra cash in the car (new fuel pump, lines, brakes, etc..) I decide to re-try it a couple of weeks ago. Well the flooding problems gone but others have showm up. I can't set an idle speed below 800rpm, with the secondaries fully closed, and the primary screw ALL the way out. She surges at idle and under light throttle, and I can't get the accel. pump adjusted correctly (tried every holley pump cam made and shooters from 25 to 35). Any ideas, please

 

[Gud T.B. Blown]

sell it and get a holley. seriously, that's what i just did. the car came witha mighty demon 750 and after 3 months, many $$$$ and no results i gave up and bought a holley 750. best move i ever made. now i have to get rid of the demon.

 

[tweet66]

I'm leaning toward doing that . Maybe I'm expecting too much but i figured if you spend that kind of money the damn thing should work fairly well out of the box with some mild tuning My only problem is the car is my daily driver so I need to at least be ableto get to work.

 

[Gud T.B. Blown]

if you're looking for true out of the box performance go with an edelbrock, it's perfect for a daily driver especially on an un-modded car. the drawback is that you really can't upgrade them (re-jetting etc..) as you upgrade your car. a holley will require a little tuning out of the box but no too bad, but they are tons of parts to upgrade them. demons require a lot of work out of the box, and even they admit it. and from what i've seen from other posts in other forums they have a BIG problem with stumbling off of the line. the newer ones are SUPPOSED to be better but apparently not. demons seem to be more for drag racing where you leave the line at full throttle.

 

[foghorn67]

the problem with demons, is they are from a billet design, which is good most of the time. the problem is that BG isn't good at getting all the small flashings out of the float and needle assemblies. My road demon 725 had it's secondary float stick, flooding the carb. we took apart the carb found the flashing, and slapped it back together, and it worked fine. problem on my part is that 725 is way too big. I ordered a holley street avenger 670. best carb I ever owned. even better then my carter (same as the ebrock carbs)
I would take apart the float assemblies and look for shiny flashings before you dump more money in a carb. the ilding and stumbling can be solved, but it isnt easy. they since changed their carbs to address this.
I would go with a holley single feed, side float 4160. I have one as a backup, and it's great. Set it and forget it.

 

[tweet66]

I have Road Demon on my 66 coupe, with more mods then the wagon will see, maybe ,and its incredable the difference from the old Holley. I have none of the problems with it that I'm having on the wagon,thankfullly. I have headers, a cam, duals and Flowmaster mufflers, and gears for the wagon but don't have the time right now to put any of them on. I'm hoping some of the changes to add performance might make the Demon respond better and I really don't want to buy another carb. I have a Edlebrock lying around from my 74 Bronco, I'll give that a try. Thanks

 

[tweet66]

foghorn, considering the fact that I've contacted them with this problem I'd like to see their customer service step up and fix it or replace it. Telling me to rebuilt the thing multiple times when they know there are problems seems like a cop-out to me. Maybe I'm wrong but having worked in customer service for many years and this is not the way I'd treat a customer or like to be treated. I didn't even run the carb all winter because of the problems. I used the original 2 barrel and an adapter to the 4 barrel manifold so it would be reliable.

 

[Great68]

My demon had the float flooding problem as well, barely made it home one night.

I just took the needle and seat out, sprayed it with carb cleaner, put it back in and never had that problem since. I agree for a carb that is *supposed* to be better than a holley, you'd think they would have better quality control.

I just bought a jet kit, can't wait until the weather gets better so I can tune those a bit.

 

[nds03]

i HAD a demon on my car, took about a year before i actually got it to run right. it was a 600 double pumper speed demon. these carbs are a pain in the ass. i did find those little shavings of aluminum from the cnc machine in the passage ways. my speed shop wont even carry them anymore. they told me to sell it to someone who "doesn't know" and holeys always outperform them, and they have a chasis dyno. now i have an edelbrock, i think once i get the elec. choke hooked up it will run fine, out of the box

 

[ron67fb]

OK tweet I'm looking back into this thread after you mentioning your carb in another thread. How exactly did the flooding go away after re-trying it? Magic? Or did you do something different? The surging and high idle sounds like a rich problem, possibly related to the flooding problem.

Do you have an electric fuel pump? Remove the carb from the baseplate and turn the pump on. Is fuel leaking out the bottom? If you have a mechanical pump, disconnect the coil wire and crank it with the carb off the manifold. You should see no fuel coming out whatesoever under the carb.

When the car is running, what effect do the idle screws have? Does the car die when you close the idle screws all the way, as it should, or does it stay running?

Let me know what you've done, step by step, and we'll try to figure it out.

 

[foghorn67]

foghorn, considering the fact that I've contacted them with this problem I'd like to see their customer service step up and fix it or replace it. Telling me to rebuilt the thing multiple times when they know there are problems seems like a cop-out to me. Maybe I'm wrong but having worked in customer service for many years and this is not the way I'd treat a customer or like to be treated. I didn't even run the carb all winter because of the problems. I used the original 2 barrel and an adapter to the 4 barrel manifold so it would be reliable.

no, you are right. Bad customer service is no excuse.

 

[tweet66]

ron67fb, I wish it was as easy as waving my magic wand sometimes I replaced 4 sets of needle and seats, cleaned the metering block and left the carb off all winter until a few weeks ago (not that the last applies). I haven't had the problem since. I'm running the mechanical pump with a regulator set at 6 psi, but I'll pull the carb anyway and check. If I turn the mixture screws all the way in the idle gets crappy but it never shuts off. If I run with them turned in any less than 1 full turn it is down on power and will surge under any throttle. I'm runing the supplied 52 primary jets and it doesn't have a secondary metering block.

 

[ron67fb]

This sounds basic, but are you sure your linkage is letting the carb close all the way at idle? Have you tried setting it with the linkage disconnected?

 

[tweet66]

Yeah I set it initially without the linkage hooked up, until I made my new linkage with heim joint ends. I also pulled the carb and cranked it over and I have no fuel seepage. I noticed she also stumbles at all rpm when the throttle is pressed. Just cruizing and push the pedal to go and stumble If I really get on it she almost shuts down. I have to let off and feather the throttle. I don't have any backfire though.

 

[Blown4.6]

Yeah I set it initially without the linkage hooked up, until I made my new linkage with heim joint ends. I also pulled the carb and cranked it over and I have no fuel seepage. I noticed she also stumbles at all rpm when the throttle is pressed. Just cruizing and push the pedal to go and stumble If I really get on it she almost shuts down. I have to let off and feather the throttle. I don't have any backfire though.

I'm having the same problem with my BG 525....bottom line is this: Barry Grant sucks. I've seen too many problems that are identicle while searching for the solution to my problem. I'm buying a new carb. Barry Grant sucks!

 

[ron67fb]

How's fresh are the tune up parts for your engine? I had a stumble like you describe and I searched high and low to get rid of it, and it turned out to be a melted plug wire that was shorting out against the header.

Not a good sign when a speedshop tells you they won't carry BG carbs anymore.

 

[tweet66]

demon stumble

ron67fb, the tune was 3 months ago. I pulled the plugs thsi weekend and all look good, maybe a little lean with white ceramic and ash colored electrodes but that could be from additives. The stumble is getting progressively worse. I reset everything by the instructions then locked out the secondaries to make sure they weren't affecting anything. That made no difference. She accelerates really well with lite throttle, but when I get on it forget it. Wounder if I should try a different PV since I'm running the 6.5 that came with the carb and I'm pulling 18" of vacuum at idle in gear. She could be going lean under heavy acceleration?

 

[tweet66]

Blown4.6, I'm inclined to agree with you on that its just weird that I've had no problems withthe 650 cfm Demon on the Stang but this one's going to drive me to drink . By the way how's the weather in O-town? I miss going to all the cruises all year round down there. I was in Winter Park for 5 years and went to all the Mid Florida Mustang cruises with the Stang.

 

[06cobra]

Ok i'm not a big fan of any of the Carbs on the market, but for tunability the demon is the best. The problems you are describing a pro carb mechanic can get that thing running like a top in a matter of minutes.
Carb rebuilts are nothing but a bunch of new gaskets and a good cleaning. So The reason they Maybe suggesting a REBUILD is it sounds like you maybe sucking air in somewhere, have a goof'd power valve, or just have the thing over jetted.

The aluminum design does have its drawbacks, mostly heat related.

Edelbrock, are the old Carter carbs, only good thing about them is the fact they don't have large fuel blows to bake the fuel. Tunablity, they are on the bottom end of the list. For a mild build they are fine, but anything that has aggressive cam specs, and high fuel upon throttle demand, they fall flat.

Good luck.

 

[nds03]

whatever you do, dont buy the tuning book for demons. its just full of theory on how carbs work, aand not how to tune them