my77stang

trying to go by memory and its been years since i mucked with the advance stuff on my dizzy.....

please correct whatever is wrong:

the advance should be connected to timed vacuum.....
even at an idle, there should be some vacuum there - because i swore when you hook the advance up after setting the timing the motor would smooth out as it advances.....
baseline with advance hooked up should be in the 6-10 degree range.

my problem is, at idle there is ZERO vacuum in the timed vacuum port, so when i hook the dizzy up to it obviously it doesnt change a thing. if i hook the advance to full vacuum from the carb it advances too far and it wants to die.

with it hooked up to timed vacuum, or with it unhooked completely - when i try to drive the car and give it some gas it sputters and stumbles and runs like crap. if its in park and i snap a quick rev it ocassionally pops out of the tailpipes.

i watched that whole damn barry grant DVD and confirmed that it really IS the worst video production of any sorts ever made by anyone at anytime ever in the whole history of ever...... ever

i did learn something about the air bleed holes and toothpicks which i have seen done but never knew the meaning - course i forgot what the specifics were because of how lame the movie was but it had something to do with detecting lean conditions.

help, before i tear this thing apart to find out why in the hell it wont work right

Colorado_Mustang

Your car should run without the vacuum advance hooked up at all. A vac dizzy won't be as smooth at part throttle, but the difference won't be as you described.

You shouldn't have any vacuum on a timed port at idle, so you're good there.

I would make sure your timing is solid for one thing (no slack in the timing chain, tight dizzy, good weights in the dizzy, etc.). No use trying to tune something that can't hold it.

You may be having issues with your accelerator pump(s) as well. Too lean and it will fart and miss very similar to a timing issue. I've yet to mess with a BG carb (Demon), but they should have all the adjustments of a Holley. Just make sure your accelerator pump cam isn't too loose/tight and allows the pump to work as it's supposed to. I think this carb is new to you, but you may want to tear it down and blow out the ports just to be safe.

my77stang

i've checked the weights in the dizzy, and even put the stock (heavier) springs back in to make sure it wasnt advanceing at all at an idle.

but to confirm, the advance SHOULD be hooked to the timed port right? i coulda swore when y ou plus it in the timing SHOULD advance a little and the motor should smooth out some.

btw im running a gear drive so theres no slack there

my77stang

update (if anyone actually cares)

after alot of reading and talking with accel it was decided that i needed about 35 deg. total timing no matter where the basline fell. this left me with either 5 deg or 15 deg depending on how the mechanical advance was setup, and it was also agreed that 15 would be MUCH better than 5.

after removing the dizzy and knocking out gear roll pins i realized that all i had to do was remove a clip on the top if the dizzy shaft covered in grease to swap the advance around. took care of that and gave everything a good cleaning while it was apart. plopped the dizzy back in and realized that my whole life i had fought the oil pump driveshafts for no reason..... just line up the dizzy to cam gear and then bump the motor over a few times until the driveshaft falls into play (was i the only one doing this the hard way before?)

fired up first try, and with idle at around 800-850 i set the timing and locked her down. i have yet to mess with the vacuum advance, but i did find the baseline settings for adjusting the vaccum canister and i will play with that next.

onto the carb - BG says 1.5 turns out is good, but mine sure doesnt like anything over 1 turn. i checked the plugs and while they are almost new they looked clean like clean clean clean. that plus plugging the air bleed holes makes it want to stumble tells me its still lean, but when i open the screws up at all it starts ******* out on me. hell, i noticed that when i close the hood it even bogs down a little, and the hood is high enough up above the carb for a low profile air cleaner to fit....... WTF?

off idle snap is real good right now, but its still flat when romp on it - definately closer but i feel like i've exhausted most of my tuning options.

JMD

I care, but I dont know if I can help, I think you are already over my head because I don't know squat about Demons, sounds like you have the dist. under control though!

my77stang

other than the vacuum advance i have the rest nailed down *i think*