Demon Carbs

[turnpike boy]

Roscoe, you a horsepower fan too, huh?

Straight links primary/secondary great for power curve, but mighty sh*tty for the financial curve (read: gas consumption). This is not to say that I wouldn't do it; far from it. But not yet. It's easier to get the metering/fuel flow needs right before going that route. Besides, I'm like Evan, a f'kng waxer (only got a 302) and don't want to scare myself into pooping in inappropriate places.

[emptor]

I'm glad someone finally brought up these carbs. I'm on my second BG Speed Demon 650 on a 351W and still having problems. The first one's throttle plates would stick when the motor got hot but ran well otherwise after some jetting changes. The second one (with a wooden block) stopped sticking, but weeps fuel down the manifold from both float bowl seals. I'm not talking about alot of fuel, but enough to cause the red die that must come from the seal to leave stains on the manifold and tiny little pools of fuel in the valleys after a whole day of driving.

In addition, the engine starves and almost dies during hard stops. The float levels are good, yet if I don't heel and tow to keep the revs up during hard stops, it stumbles.

And lastly, this second carb doesn't run as well as the first one even though all the setting are the same. It idles and starts well, yet boggs sometimes under the pedal and never seems as 'clean'. My SPF has never been dynoed, so I have no benchmark to go with other than the seat of my pants, but last time I had it calabrated it was on the money...

Any ideas??

[George Snyder]

Turnpike Boy,
Yes I am coming to the revolution on the 7th. I am really looking forward to meeting you and others there.

Demon Tech told me to use the secondary idle screw more to help stumble, and it worked. I realize that all you are doing is exposing more of the idle transfer slot. I didn't know about the effect it would have on the idle circuits. It helped me though, and when I ran the car on the chassis Dyno the A / F at idle was was 13.97. I was told 14 is about perfect. My A/F graph was pretty flat, but a little lean high peaking at 14.1. Hence the jet change. I haven't run it since then to be sure the lean condition was corrected. My idle mixture screws seem to be set at a relatively normal location.

Is your carb installed directly on the intake or do you have some type of plate between? Performer intakes are notorious for have trouble sealing properly with carb to intake with one gasket.
On the sbc I added a cheap Mr. Gasket 1/8" steel plate in between. The 302 utilizes a solid chrome plate between which also is the throttle linkage mounting point. Just a thought.

A comment on Roscoe's 1-1 linkage!

What he forgot to mention is that he is running AFR Heads, which I am sure are flowing alot more, I mean alot more air than ours. I doubt my GT40X heads would support that set up without problems.

If you are still experiancing problems when you come to the revolution, we can always distract Roscoe for awhile and exchange your demon for his!!! A couple bucks to a few Hooter Girls from King of Prussia would probally work. Of couse we will use new gaskets, we wouldn't want to take advantage of a fellow Cobra Owner!
Bud

[George Snyder]

emptor,

I do not have a clue what is causing that problem, but I will ask around and try to get you an answer.
Bud

[Mr.Fixit]

Your stumble may be cause by a lack of the long type of vent baffle in the secondary float bowl. If you don't have the long vent baffle get them.

[flipper35]

http://www.4secondsflat.com

There is a good tech article for tuning BG carbs. Or you can talk to him, his name is Don Gould. He has a 'Cuda that runs close to the 11's with an all iron 318.

He also has a working partnership with BG and may have more insight for you.

http://www.4secondsflat.com/demon101.html is the tuning page

[turnpike boy]

Actually, Brent, this is better than good. No subtitute for experience, and this man appears to know his stuff. Have now printed out his info and will apply as quickly as I can...Thank You Much.

[flipper35]

Your welcome, hope it helps. He has wrenched on Nascar CTS and Cup cars as well as WoO and his own sprint car and seems to be pretty knowledgable.

[emptor]

Thanks George - I'd like to hear what you come up with!

[ronzara]

I have A ROAD DEMON 625cfm on my (As of now) STOCK 1971 351W. This replaced a 650 Holley DP that was WAAAAYYYY TOO MUCH carb for the motor.
The DEMON was Very Rich right out of the box. (I think BG under rates the flow of their carbs).
We have adjusted the fuel levels down A LOT, but, now the motor has VERY quick throttle responce, smooth idle (READ>no loading up), and has no flat spots.
This motor is soon to be mated with a Weiand Stealth Intake, SVO X302 Heads, and a Comp Cams .500 lift cam. >>>> this setup should let me "open" the carb up a little. Can't wait to see what how it will handle more HP.
HAPPY TUNING!!
RZ

[cuda66273]

I see my name mentioned here and I'd like to invite anyone that has a Demon Tuning problem to give me a call and we'll see if we can determine the problem and correct it for you...we tune these carbs every day and have no problems that can't be easily resolved.

You can visit the tech section of my web site and click on the Demon 101 article.

www.4secondsflat.com

Email me at
bigdaddy@4secondsflat.com
or call the shop 7am to 7pm monday - friday. 503-627-0728

If you purchased a Speed or Mighty Demon this year you probably have the Idle Eze valve installed from the factory.

BG has no tuning instructions yet for this feature......I do :-)

I'd be happy to send them to anyone who wants a copy of my step by step tuning preceedure on carbs with this feature.

The only problems we really see with these carbs are "Sellers" errors, wrong type or size for the application.

If your considering a Demon Carb call a reputable dealer who tunes these things and can help you out with the correct series and size for your application.