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Author Topic:   Demon Carb-Stumble in corner
jbell7
Dirt Newbie

Total posts: 2
posted August 05, 2002 11:52 AM
Street stock so have to comply with 16in vac rule. 383 sbc with hyd cam/Rhoads lifters. 487-517 lift. This is Speed Demon 850cfm. Carb stumbles bad in corner,kick it with pumps and runs very good on straight. Came with 80pri and 85 sec jets. Tried 74-80 close to same thing in corners. Float set half way in sight glass then changed to upper limit in glass. Same stumble. Tried setting four corner idle screws. 1 turn sec/,,,1 1/2 pri. Could this need leaning out of idle by tapping in idle plugs??? I think this carb is too complicated for me to run!!! Any tips would really be appreciated. BTW!! Ran old Holley 750 Sat night and ran very good. Thanks Jaybe

dirtbuster
Dirt Freak

Total posts: 353
posted August 05, 2002 12:29 PM
You should keep you fuel level at near the middle of the sight glass and make sure you check it with the engine revved up a little at operating fuel pressure.

What is your fuel pressure?

Does it stumble when you try to get back on it then clean itself out and go? Like it is getting too much fuel?

Or does it hesitate like the accelerator pump isnt set right?

autoshop
Dirt Maniac

Total posts: 102
posted August 05, 2002 01:16 PM
try fatting up the idle screws on the primary side at 2 turns, that will help the stumble off idle. Also try resetting the accel pump shot by either going to the bigger squirter or changing the the shot timing.

jbell7
Dirt Newbie

Total posts: 2
posted August 05, 2002 06:36 PM
Thanks for the reply "dirtbuster" and "autoshop". Fuel pressure is 6 lbs at idle with holley regulator. My son drives this car (first time driver) so its hard to say if its lean or too fat in the corner. It cleans out good on the straight with a shot from the pump so kinda sounds lean huh. Primary looks like it opens about half way before starting secondaries so I think that would help vac signal at lower rpm,,maybe not though. I'll reset the pri idle screws to 2 turns and try that. Also may reset the pumps. Quicken them up a bit. Thanks again for the fast replies. Very good forum, especially for a retired old dummy..lol. Jaybe

dirtbuster
Dirt Freak

Total posts: 353
posted August 06, 2002 09:27 AM
Do you have the pump levers set to where there is no clearance between them and the pump diaphragm. They should be just touching and have no play between them potherwise it will delay the pumpo shot until that clearance is taken up.

What kind of fuel pressure do you have at speed or at least when you rev the motor up?

We run a Demon on our mod and have gotten along great with it. Sounds like you just need some fine tuning. I dont think you need to change anything with the idle plugs. We took ours out of the box and threw it on and didnt change anything and it runs great.

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