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Old 04-13-2008, 08:29 PM
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Mighty Demon

Ok I have to start off with saying im new to carbs. I know how they work and everything but I havent been around them long enough to get any practice tuning them. Im 21 and carbs arent really my day and age
I have a 650 Mighty Demon on my 383 I just built for my 69 camaro. This was my first engine build/project. I cant seem to get the thing to stop running rich. Like smokey watering eyes feel like your about to pass out rich. I had the idle air screws out 1 1/2 turns from being all the way in as a starting point. I know these carbs have the "idle ease" screw at the bottom of the air cleaner stud hole. Will this help me with mixture though? Fuel pressue is like 6psi. I was thinking about turing it down a tad. I figured I would post somethin here before I did anything else b/c I know these are popular carbs and Im sure you guys have had some expiriences w/ them. Ive also heard these carbs out of the box can be great w/ little adjustment to get running right or they can be a real pain in the ***. I just dont wanna lean the thing out. Any advice is greatly appreciated.

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Old 04-13-2008, 08:48 PM
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Idles rich

It sounds like it could be the power valve.If the cam is big enough to effect engine vacuum and it has the wrong power valve it will have an excessively rich mixture.I would highly recommend buying a book on power tuning carbs.Ofcourse this could be just one of many potential problems.
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Old 04-13-2008, 08:56 PM
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Quote:
Originally Posted by BORTI
It sounds like it could be the power valve.If the cam is big enough to effect engine vacuum and it has the wrong power valve it will have an excessively rich mixture.I would highly recommend buying a book on power tuning carbs.Ofcourse this could be just one of many potential problems.
Could be, its a 292 magnum. I know that has some effect on the vacuum.
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Old 04-13-2008, 09:03 PM
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Idles rich

That is a decent size cam,so you may have to change power valve or set the idle up just a tad.
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Old 04-14-2008, 03:34 PM
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Ok thanks for the tips
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Old 04-14-2008, 05:20 PM
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Put a vavuum gauge on it hooked to manifold vacuum and pick a power valve about 2 to 3 inches lower than that in it.That will get you in the ball park there is a formula to use on holley's website to get the exact valve you need.If you are used to fuel injection just remember a carb IS a mass air metering system i.e power valve works like a map sensor sensing load because of low vacuum it adds fuel just like an ecm would, bigger and smaller jets are just like running with no o2 sensor in open loop only the jets tell how much fuel instead of preset ecm program, choke would = cold start enrichment system-imprperly set choke will act just like a bad ect sensor.Accelerator pump equals tps movement rate adding fuel on tip in.Float or fuel pressure to high will also act like a bad map or ect allowing to much fuel at all times.Hope this helps.
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Old 04-14-2008, 07:30 PM
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thanks for the help
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