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#1
07-15-2003, 02:58 PM
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I just adjusted the timing on my 70 GTO (400/350) with 4bbl carb. Now I'm having a heck of a time getting my fuel mixture correct.
When I stand facing the carb, there are two mixture screws directly under the air cleaner, one on the left and one on the right. I think that one is for the fuel and the other is for the air, but I can't tell which one in which, and I'm not sure which way to turn the screws (I think clockwise is to close, and counterclockwise is to open). It is running pretty rough, and I'm smelling gas from the exhaust, so I think I need to get more air and less fuel. Can anyone provide some advice as to how to proceed? Thanks, Harry Harry's 70 Dream
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REDGOAT 70 1970 GTO 400/350 TH400 |
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#2
07-15-2003, 02:58 PM
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I just adjusted the timing on my 70 GTO (400/350) with 4bbl carb. Now I'm having a heck of a time getting my fuel mixture correct.
When I stand facing the carb, there are two mixture screws directly under the air cleaner, one on the left and one on the right. I think that one is for the fuel and the other is for the air, but I can't tell which one in which, and I'm not sure which way to turn the screws (I think clockwise is to close, and counterclockwise is to open). It is running pretty rough, and I'm smelling gas from the exhaust, so I think I need to get more air and less fuel. Can anyone provide some advice as to how to proceed? Thanks, Harry Harry's 70 Dream
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REDGOAT 70 1970 GTO 400/350 TH400 |
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#3
07-15-2003, 03:52 PM
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The two screws you see are the idle mixture screws. One runs the left side of the carb, the other the right.
A good rule of thumb, if you want to reset the idle mixture, is to seat both screws lightly (turn them in clockwise 'til they just stop. Don't turn them in tightly!), then back them out four full turns. Start the car and turn each screw in 1/4 turn at a time, going from the left, then to the right, back and forth 'til you notice a slight stumble in the idle. This stumble means that you've leaned the mixture out enough. You then back the screws out 1/8 turn each. This will be your final setting. If you did this correctly, both screws should be the exact same number of turns out from the seated position. That's all there is to it. If you need more info, there's a section, under 'engine fuel' in your service manual that explains how to do this. If you don't have a service manual, I'd recommend that you get one. It's a valuable source of info. .............................. |
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#4
07-15-2003, 07:32 PM
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you can also use a vacuum guage hooked to a common manifold vac source. adjust both crews until you get the highest vac reading possible. you may have to go thru both sides a couple of times to get this.
mike
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so many pontiacs, so little time.................. moderator is a glorified word for an unappreciated prick.................. "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." --Albert Einstein "There is no such thing as a good tax." "We contend that for a nation to tax itself into prosperity is like a man standing in a bucket and trying to lift himself up by the handle." - Winston Churchill |
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