Carb advise Pls!!!

[Franko]

Hi Everyone
Just got my Cobra with a new 466 crate motor running and I need a little advice. It has a Demon 750 Carb and Im running 91 octane gas. It is hard to start and it continues to run for a few seconds after I shut it down (. Timing seems to be right on the money. Any advise would be great!!

[BEB]

You should have around 18/20 degrees initial timing.

Demon carbs like more initial timing than other carbs to work at their best.

[Big-Foot]

It sounds like you have the idle set just a little too high. When you have a cam with a longer than stock duration, you typically need more air at an idle, but can't get more air without giving it more fuel to boot. I would advise adjusting the throttle stop for the secondaries to open them just the slightest of cracks so you can turn the idle speed screw in the primaries down far enough where the main metering system can go back to rest at an idle. If the screw is turned in too far, you have uncovered the fuel transfer slot for the primaries and it is now running very rich for a low RPM. That will the cause run-on (used to be known as Dieseling) condition you are experiencing.

[mj_duell]

Originally posted by BEB


You should have around 18/20 degrees initial timing.

Demon carbs like more initial timing than other carbs to work at their best.

How true it is! Had all kinds of issues until I ran the initial that high. Runs like a top now. FE's love advance as well. also, checkout this website by Don Gould. He was a great help in tuning my Mighty Demon and setting up the timing.

http://www.4secondsflat.com/demon101.html



--Mike

[Big-Foot]

Originally posted by BEB


You should have around 18/20 degrees initial timing.

Demon carbs like more initial timing than other carbs to work at their best.

A Carburetor is simply a device that mixes fuel with air and is dependant upon the flow of air and vacuum to work properly. If you have to put that much initial advance into your engine to make it work, it's because you are putting a band-aid on another problem.

The carb and it's function are not impacted in the slightest way by timing.

I would suggest that if running a lot of initial advance makes your engine run "right" that you take a look around for other problems such as vacuum leaks. Also you could also benefit from using a vacuum advance distribuitor with the vacuum advance unti connected to manifold vacuum. This will give you a much higher initial advance that is variable depending upon vacuum - thereby reducing the opportunity for detonation to cause irrepairable damage to the engine.
Having had a med-riser 427 that was severly damaged by running too much initial advance and no vacuum advance - I know that FE's are not impervious to the problem..