Hey guys, I am running a brand new Street Demon 750 carb on my 360 Magnum. Stock Heads, 5.9 Whiplash Cam. Air-Gap intake. I can't quite cure the Rich Idle, I have heard that Demon and holly carbs in general tend to run rich out of the box. I have tried to use some google magic to get some help but the street demon 750 is newer to the market so there are not to many write up's on them yet...

From what I have gathered a rich idle shouldn't be a jet/metering rod issue, it should be a tune issue. I have the timing set where it starts right up at the bump of the key... any suggestions... maybe more Fuel/Air screw adjusting?

I am in Phoenix so we are only about 1,200 feet above see level.

What is your initial timing?

Idle mixture adjustment is done with the metering screws. How many do you have (2 or 4)?

I'd elim float setting and psi. yes you need enough initial to have the throttle closed enough to not be in the mains/transition? circuits at idle speed. how many turns CCW (out) till the throttle JUST stops moving

Hey guys, I will check float and see where I am in initial with the light. Heading out to the shop now, will post more hard numbers and my finding's in a bit. It is a two screw adjustment.

Yup. You're on the right path. Getting the engine to fire is OK, but next you have to set it for best combustion. With a somewhat radical cam, it will need a richer than stock mixture and a bit more initial idle timing (than stock).
Use the charts on this link with your cam's duration to get a ballpark for the initial timing.
http://www.demoncarbs.com/Tech/DemonSelectionGuide.asp

The Street Demon is new but the principles of its operation appear to simply be a rework of the Thermoquads and its predecesors. You should be able to get the idle and off idle by adjusting the throttle position (aka idle speed screw) and the idle mix screws - once the timing and fuel level are where they ought to be. If you find it drops rpm a bunch when you put it in gear, then its too lean (and probably a bit too much timing) to make power at idle.

If you're curious about Air/Fuel ratio vs. load this post will help.
http://racingfuelsystems.myfunforum.org/...d_about421.html

Also some folks on that forum that can help if you do need to do some tuning with that carb. Q-jets, t-quads, and zeniths are not feared or shunned there.

Thanks Mattax!

What's the overlap on that cam? If you have a lumpy idle, there may be enough pulses in the intake to keep the idle stinky. Do you have an O2?

My Street Demon is very sensitive to fuel pressure

Even with the Carter low pressure (rated at 6psi) electric fuel pump that was fine unregulated on my Eddie 1406 the Street Demon wasn't working right.

At the advice of the Demon tech line I put on a regulator & gauge, reduced the pressure to 5psi and now it runs nicely

Interesting...."Demon Carburetion® & BG Fuel Systems are registered trademarks of Holley Performance Products, Inc"

Love the new TQ Demons. we used to manipulate the TQ tree height screw for global A/F changes. Idle is all mixture screws..