Demon carb?

[JoeGrapes]

I have a 750 Demon on my 440. It's a  mechanical secondary electric choke. I've been screwing with this thing for years and can't get the off idle bog out of it. On my 4 speed car, when starting off from a stop you have to feather the gas and the clutch to get it to go. If I open up the idle screws enough to stop it, it will run real rich. I've tried every way the book says to adjust it. I'm about ready to toss it in the lake and go back to my Holley.

[cameron2502]

sound like it needs more accelerator pump shot

[BIGSHCLUNK]

Or if your lucky like I am... incorrect secondary throttle plate adjustment and way to small squrters... You could chase for years w that secondary thing and not find the prob is what a holley guy told me. This is on a 750DP I canr see the demon being that diff.  Start w the pump shot....... 

[moparmaniac59]

I had a Demon & had the same stumble problem. Have you tried making any adjustments/changes to the air bleeds??

[Chryco Psycho]

I would exorcize the Demon & install a Proform
 I have numerous Demons that simply could not be tuned or stay tuned , I even worked on Rev & Redlines Chall , we would adjust the carb in the morning & by noon it would be running badly , adjust it back at noon & it woul dbe running badly by supper time , we were simply adjusting it lean then back richer 2-3 times / day , we finally installed a new Holley had it tuned in 1/2 hr & it stayed tuned for 2-3 years with no issues .
 Demons are Garbage dump them in the trash & get a real carb .

[moparmaniac59]

  I sold mine at Carlisle last year. I hope you weren't the one that bought it!! 


                                                                        Matt B.

[MEK-Dangerfield]

I sold mine at Carlisle last year. I hope you weren't the one that bought it!! 


                                                                        Matt B.

       

[HP_Cuda]

It's funny that Demons and Proforms follow the Holley almost to a tee.

But setting one up for the long term is definitely the sweet spot of the Holley.

Put the demon on ebay and grab a 750DP if you like the little fun pedal.

[JoeGrapes]

You are right Psycho, I've adjusted that thing to the point that it was running good, then the next day ran like crap again. I have a 750 Holley that I'm going to put back on. No Matt, I didn't buy your Demon. I've had it for about 6 years now and it never ran right.

[73restomod]

I've had Holleys do the same, check the threads and the springs on the mixture screws, and the metering blocks. As far as the bog sounds like your pump shot is timed wrong or to small. I will admit that when it comes to a demon Carb they work great or they don't work without being rebuilt right out of the box. Can't say I have any experience with the newest ones.

[brads70]

I have a 850 Demon on my 440 seems to work ok for me? I have heard lots of complaints about them though? I did tear it compleatly down when I first bought it( used) and did find machining chips in the metering block. Spent some time inspecting and deburring a few area's to get the chips out .

[73restomod]

Same here, I bought an 850 vacuum secondaries annular boosters, first thing I did was a complete tear down and inspection . The Holley that gave me fits was a brand new 675 truck avenger, I ended up having to get new metering blocks for it. Not knocking Holley, just pointing out that even they can have issues, its just more rare. After fiddling with Holleys and Holley like. Carbs for over a decade the biggest problem I've seen involves overzealous screwdriver tightening on the mixture screws.  After that good luck getting any Carb to hold its tune. 

[Chryco Psycho]

I too have run across a number of Holley carbs that can be impossible to tune so yes it happens to all carbs & mfgs , as you said it is far more common with the demons though . When I talked to Summit racing in person the people there told me straight up that they could not continue to sell Demons simply because of the warranty issues with them . I spent some time on the phone discussing the problems with a tech @ Demon & he did not discuss the problem directly with me but instead just ran down a checklist of what I had done to tune it , After I had said yes to about 25 questions when I finally said no to one he said there is the problem & hung up on me .

[HP_Cuda]

Wow now that is customer service!

I have never had a problem with a brand spanking new Holley out of the box.

Can't say that for other carbs though.....