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88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.


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jumaica
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Dec 6, 2010, 8:32 PM

Post #1 of 10 (2088 views)
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88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. Sign In

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, 9:40 PM)


re-tired
Veteran / Moderator


Dec 6, 2010, 11:02 PM

Post #2 of 10 (2074 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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 7, 2010, 12:19 AM)


jumaica
Novice

Dec 7, 2010, 6:40 PM

Post #3 of 10 (2066 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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?


re-tired
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Dec 7, 2010, 7:03 PM

Post #4 of 10 (2065 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

Here is the Demon site should have all you need.


Welcome to Barry Grant - Home of Demon Carburetion, BG Fuel Systems, NitrousWorks and Rush Performance Filters.


LIFE'S SHORT GO FISH


jumaica
Novice

Dec 7, 2010, 8:07 PM

Post #5 of 10 (2061 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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?


Hammer Time
Ultimate Carjunky / Moderator


Dec 7, 2010, 8:13 PM

Post #6 of 10 (2057 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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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jumaica
Novice

Dec 7, 2010, 9:22 PM

Post #7 of 10 (2054 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

I know right! Thanks anyways.


re-tired
Veteran / Moderator


Dec 7, 2010, 9:53 PM

Post #8 of 10 (2043 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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, 9:55 PM)


jumaica
Novice

Dec 8, 2010, 10:49 AM

Post #9 of 10 (2039 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

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.


jumaica
Novice

Dec 8, 2010, 10:58 PM

Post #10 of 10 (2030 views)
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Re: 88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me. [In reply to] Sign In

Ok the problem was the power valves. Thanks a mill guys.




88 chevy mc ss. 305. black smoke and burns fuel super fast. please help me.


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