Thread: speed demon carb bog

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okay i picked up a speed demon 850 from a swap meet. i went threw it and it and it idles way better than the edelbrock. what cauese the stumble. if i stall the car up to 3000 it takes of great but when crusing or in park if i dead stomp it it cuts out and then revs fine to 7000. would that be the shooters it has 31 primary and secondary. would it be the pump cam?

power valves ?

some questions

what size and equipment is your engine???

Does the carb have an Idle eze adjustment?

Double pumper??Oh yes it is .031 squirterS

how did you set your idle speed?
How far open are the transfer slots?
What power valve is in it
does it have the pink accerator pump cams
choke tower?

worked on fine tuning a 1000cfm mighty demon today and everything is fresh in my mind
get back with the info I asked

accelerator pump cam would be my first area to check.

i have a 5.5 power valve with 11 inch vac
pink pump cam 83 pri jet 85 sec jet
i set the idle at 1000 rpm working back from pri and sec and then worked idle mixtures
its a older speed demon with a small tower 850cfm
496 bbc 10.2 comp comp solid roller .653-.660 lift merlin oval heads, rpm airgap intake. the car would barley idle with the edelbrock after the cam swap

Originally Posted by 6801

i have a 5.5 power valve with 11 inch vac
pink pump cam 83 pri jet 85 sec jet
i set the idle at 1000 rpm working back from pri and sec and then worked idle mixtures
its a older speed demon with a small tower 850cfm
496 bbc 10.2 comp comp solid roller .653-.660 lift merlin oval heads, rpm airgap intake. the car would barley idle with the edelbrock after the cam swap

is that 11inch vac in gear ? if not go smaller

Make sure you have full pump stroke on the accelerator pump. When I bought my Holley-new, the pump cam was upside down and would only travel 1/8", so I had a big bog on tip in.

try this set the throttle stop screw at 1300 rpm in neutral adjust idle mixture screws to best idle at 1300 rpm now lean idle mixture screws equally about 1/4 turn each until you get back to 1000 rpm do not touch idle stop screw. this will move the throttle plates closer to the transition circuit if that eliminates the bog great but if it only helps try 1400 rpm this method works if not you need some carb changes .....ted

its raiy again in ohio so i cant drive. i changed the shooters 35 primary and 37 secondary its deffenatly better. i diidt touch the idle

Originally Posted by 6801

its raiy again in ohio so i cant drive. i changed the shooters 35 primary and 37 secondary its deffenatly better. i diidt touch the idle

It's the shooters. I usually go up a little at a time until it's clean and crisp and at a lower rpm than you want to leave at....if this is a drag car. Sometimes you can get it clean in the pits/garage, but under a load the lean condition is still there. When you get to that scenario, you know you're close. Just make sure you have about .014 between the pump arm and the adjuster when the carb is wide open.

It can also be to much fuel at tip in. Put .010~.015 slack at the pump arm with the throttle closed. If that helps go to a smaller pump cam and readjust the pump arm to .015 at WOT.