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88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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jumaica
Novice
Dec 6, 2010, 6:32 PM
Post #1 of 10
(4364 views)
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88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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I own a. 1988 chevy monte carlo ss. 305 v8, 5.0 hp engine. Its been modified with elderbrock intake manifold, 4barrel demons carburator w/ electric choke, all msd ingnition system w/ 6al msd box, 8.5mm wires nkg. Platinum spark plugs gapped at 0.45, headman headers, no catalic converter stage 3 dual flowmasters with glass pack, flex fan, optima red top battery. Ok. The problem im having is it burning fuel extreamly fast at idile. Black smoke and carbon blows out the exshaust with no catalic converter. I just changed the spark plugs ( they were covered with a black carbon. ) I also changed the oil too and it was extra thin with gas in it. ( may have been due to me pouring to much gas in the carburator) I crossed up my spark plug wires by accident and started the engine it started but ran rough so i turned it off and corrected the wire order. I started the engine and it ran a little smoother but still ran rough at idle speed .as I increase the engine speed but it still blows black smoke out exhaust. The exhaust sound irratic as if it had a race cam in the engine and the engine shakes at idle also. when I screw the adjuster screws in all the way in on the carburator The engine still is running rich and starts up every time. In the past it would just cut off. any one have any idea how to fix this issue or any suggestions, please feel free to respond. And thanks in advance.
(This post was edited by jumaica on Dec 6, 2010, 7:40 PM)
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re-tired
Veteran
/ Moderator
Dec 6, 2010, 9:02 PM
Post #2 of 10
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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If you are running a mechanical fuel pump I would check for a ruptured diaphram.This would put gas in the crankcase and also add fuel vapors to come up the pcv system and screw up the idle mixture. Also what cfm carb are you running? If I remember right the demon uses a power valve in the pri metering block , it may be possible for the diaphram in it to be ruptured by a backfire. Allowing fuel into the venturi .
LIFE'S SHORT GO FISH
(This post was edited by re-tired on Dec 6, 2010, 10:19 PM)
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jumaica
Novice
Dec 7, 2010, 4:40 PM
Post #3 of 10
(4342 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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I put a new mechanical. Fuel pump on 6 months ago. The car did back fire a few time and flames came out the carb. I will replace the power valves there is two of them with two diffrent numbers.
What size power valve would you recommend ? And also is there a way to test the power valve to see if they are blown or not?
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jumaica
Novice
Dec 7, 2010, 6:07 PM
Post #5 of 10
(4337 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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They were the first ones I called. He just suggest me taking the carbon to demons carb specialist. He told me not to tamper with it, he wouldn't even tell me how to use the adjuster skrews. But im a hands on car owner and I want to learn how to do it myself. Its kind of a hobby/ addiction. Any car guy would understand.
What does the power valve do?
Whats the size of 600cc holley or demon carborator power valve ?
What should the two vacume post side by side on passenger side vacume lines connect or lead to?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 7, 2010, 6:13 PM
Post #6 of 10
(4333 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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If you really want to learn all that, it looks like you an Mr Google will become great friends.
You need to start doing a whole lot of reading.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jumaica
Novice
Dec 7, 2010, 7:22 PM
Post #7 of 10
(4330 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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I know right! Thanks anyways.
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re-tired
Veteran
/ Moderator
Dec 7, 2010, 7:53 PM
Post #8 of 10
(4319 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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Of course HT is right . But it really burns my tush when aftermarket people get snobbish , after all you bought their product. So I'm goin to give you a nudge in the right direction . You still have to read them tho. Good LUCK
How to replace power valves on demon carburator - AOL Search Results
LIFE'S SHORT GO FISH
(This post was edited by re-tired on Dec 7, 2010, 7:55 PM)
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jumaica
Novice
Dec 8, 2010, 8:49 AM
Post #9 of 10
(4315 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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Yes it does upset me about them taking my money and not wanting to tell me about the product. I have been doing some reading like u said. I found out the power valve is to be half of whatever the vacum gauge is.
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jumaica
Novice
Dec 8, 2010, 8:58 PM
Post #10 of 10
(4306 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.
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Ok the problem was the power valves. Thanks a mill guys.
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