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Old 06-07-2005, 07:08 PM
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1972 Nova Turbo Lsx
 
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Need Help with my carb mighty demon

Well after playing with this and talking tho bg off and on figured id post on here and see what you all think first off here is my setup
4 speed manual trans
355 sbc
220cc dart iron eagle heads 205/160 64cc combustion chambers
11.87:1 compression
victor jr intake
solid comp cam
msd ignition with mech adv dist. 18 intial and 38 total
.50 252/260 duration and lift 540/558 110 lobe sep


car is gutless. i have numerous problems right now it stumbles hard at idle and when on the gas heavy launch it studders hard and pops and even a small backfire it really has no good power this is a new carb. i have been through it alot and reset butterflies at the settings that it requests and also tried closing them and messing with the idle eaze but that idle eaze screw does absolutley nothing. I have cleaned it and made sure there is no trash in the bleads or anywhere. my vacume reading at the carb is very erratic like fluctuating alot between 6-10 and car just idles badly cant adjust mixture screws to get any kind of baseline. I geuss i never have had any troubles with a carb like this one. any help would be great

fuel pressure is good and floats are set also. i am really at a loss and i like bg tech but over the phone it is a fairly long wait at times and have not been a help at all here and i talked to a bg rep at the national event here in columbus and though his suggestions were good but did not help.

I tried this spacer a 4 hole 2" and did nothing for me. even with the carb set-up does anyone think that this will help with my combo to get some low end out of this. this carb is a year old now and has not been driven down the road at all becasue i cant get the car to run right. and yes all internals are good and set up right


any help is appreciated.....thanks so much
dan

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Old 06-07-2005, 07:14 PM
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Quote:
my vacume reading at the carb is very erratic like fluctuating alot between 6-10 and car just idles badly cant adjust mixture screws to get any kind of baseline

I think this tells the tale...? I`m seeing a vacume leak from hell...?
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Old 06-07-2005, 07:26 PM
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yeah not sure where at all the only vac line goes from the carb to the vac can to the booster for brakes that is it vac goes no where else..... so i dont know the engine is fesh so intake leak is not possible maybe i should do away with the can.

thanks
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Old 06-07-2005, 07:33 PM
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If no vacume leak can be found (visibly) possibly use some carb cleaner and spray around all area`s of the carb and intake...?

Also noted your running a solid roller cam... Not to sound offensive but is it set correctly...? It cannot be set like a reg flat tappet solid cam... Just asking to be sure... One more also just to be sure no crossed plug wires...?

Sometimes the basics bit us in the buns...
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Old 06-07-2005, 07:37 PM
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thanks for some suggestions
it is a solid flat tappet cam
and the firing order is right and timing
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Old 06-07-2005, 07:54 PM
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K... though it might be solid roller...?

Anyhow... Any other carbs around that can be used to check this with...? I still keep my old faithful 650 DP just for cam breakin`s and "keep it honest" testing... (but have everything from 750-1050 to play with)
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Old 06-07-2005, 08:10 PM
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Here is so tech info about Demons.
http://www.carcraft.com/techarticles/56919/index.html

tuning w/air bleeds
http://www.carcraft.com/techarticles/81958/index.html

Basic setup for Demon:
http://www.omniracing.net/html/4_corner_idle.html
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Old 06-07-2005, 08:54 PM
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Have you ran a compression test?

Have you checked blowby? (or vacuum in the crankcase...could be a sign of leaky intake gaskets)

You are sure the lash is correct?

What condition is the ignition system in? ie good 2" blue spark?

Have you set the timing by ear?
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Old 06-07-2005, 08:57 PM
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just thought of something are the holley powervalves the same as bg. i replaced the power valve with a different number and noticed the carb went even further south it was kind of ok but it is further away now just was not sure if bg runs a different power valve since the metering blocks are different.
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Old 06-07-2005, 09:31 PM
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same, same.needs to be 2 in lower than idle vacuum so it wont flood engine with fuel.id say not enough timing. put some more in and watch it work. then if it bogs put a bigger shooter in til it works and play with cams
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Old 06-08-2005, 03:24 PM
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well i geuss the last time i remember i had the car tuned decent i had the stock powervalve in it and sitting atop the single plan victor jr. so i was trying for more power and talk to some people and told them my current vac reading so the suggestion was to drop to a 4.5 valve from the std. 6.5 and then i went with a 4 hole 2" spacer. it would not run hardly and when i took off it loaded up bad and would not get out of its own way. so i took the spacer out of the equation and still the same problem so then i bought a 6.5 holley powervalve at jegs here locally and still no luck i have to go get the stock bg one and put back in that is my only idea for some reason the holley one is not working and i thought all parts are interchangable but when i put the bg power valve in it sticks through the meterblock further then the holley one i geuss my only though is the the valve is staying open or something and putting to much fuel in??? i dont really know and it is bugging me. I am just not to lucky at all with the demon carb. starting to regret purchase i can tune a edelbrock or something easy but i geuss this may be a little too much for me. if any one has any thoughts on this please let me know....thanks dan
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