302 c6 combo
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Joined: Mar 2011
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From: Portland, Oregon
302 c6 combo
anyone else with this combo run an edelbrock performer carb and manifold? when my truck decides to start...(heh) the fuel mixture doesnt seem right when driving. it used to get great, upwards of 17 mpg highway and then i decided to mess with the mixture screws on the front of the carb as per the factory manual and it just doesnt have the "pep" it used to.
the edelbrock manual isnt exactly set up in laymans terms and yo
u practically need a math degree to set the mixture to the chart specifications....as well as it all has to be done on a dyno.
anyone have some tips tricks? or point me to a forum where i can explore this issue more?
thanks all
-ac
the edelbrock manual isnt exactly set up in laymans terms and yo
u practically need a math degree to set the mixture to the chart specifications....as well as it all has to be done on a dyno.
anyone have some tips tricks? or point me to a forum where i can explore this issue more?
thanks all
-ac
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Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
By the mixture screws on the front, are you talking about just the idle mixture screws?
If so, all you need is a vacuum gauge. Connect the vacuum gauge to DIRECT manifold (not ported).
Adjust the two screws to these three specifications:
1. The highest manifold vacuum possible. The higher the better. If it comes down to it, make small 1/16 turns and wait a few moments for the vacuum to equalize and then adjust again. Keep tweaking until you just can't get the vacuum reading any higher.
2. They're turned IN as far as possible with the highest vacuum. Meaning, if 3 turns out gives you 17hg vacuum and 1 1/2 turns out gives you 17hg vacuum, you want them at 1 1/2.
3. The screws are out the same amount of turns. Meaning, if after you adjust both screws for peak vacuum, one's turned out 2 1/4 rotations and the other is turned out 1 rotation, adjust them both to 1 5/8 turns.
A side note: If any of the above adjustments change your idle RPMs, reset the idle RPMs back to base and start again. Keep going until your idle RPMs are correct and you can't make any more adjustments.
That'll take any and all guess work out of it.
If so, all you need is a vacuum gauge. Connect the vacuum gauge to DIRECT manifold (not ported).
Adjust the two screws to these three specifications:
1. The highest manifold vacuum possible. The higher the better. If it comes down to it, make small 1/16 turns and wait a few moments for the vacuum to equalize and then adjust again. Keep tweaking until you just can't get the vacuum reading any higher.
2. They're turned IN as far as possible with the highest vacuum. Meaning, if 3 turns out gives you 17hg vacuum and 1 1/2 turns out gives you 17hg vacuum, you want them at 1 1/2.
3. The screws are out the same amount of turns. Meaning, if after you adjust both screws for peak vacuum, one's turned out 2 1/4 rotations and the other is turned out 1 rotation, adjust them both to 1 5/8 turns.
A side note: If any of the above adjustments change your idle RPMs, reset the idle RPMs back to base and start again. Keep going until your idle RPMs are correct and you can't make any more adjustments.
That'll take any and all guess work out of it.
Posting Guru
Joined: Jun 2002
Posts: 1,028
Likes: 0
From: Panama City, Fl
Those two mixture setting screws are only for the idle circuit and have nothing to do with the fuel flow once above an idle. The main jets and metering rods control the fuel flow once you are above the idle/1000 rpm or so.
If you are running rich down the road, you may have come dirt in the owls or a needle valve and float issue.
Changing the mixture as you did could effect the initial off idle response due to running either to lean or to rich at idle. This can cause the engine to bog initially.
As an FYI, turning both of the mixture screws in GENTLY until they stop should stop the engine. Sometimes one will do it. If it does not, the carb is supplying fuel thru the wrong system for idle.
If you are running rich down the road, you may have come dirt in the owls or a needle valve and float issue.
Changing the mixture as you did could effect the initial off idle response due to running either to lean or to rich at idle. This can cause the engine to bog initially.
As an FYI, turning both of the mixture screws in GENTLY until they stop should stop the engine. Sometimes one will do it. If it does not, the carb is supplying fuel thru the wrong system for idle.
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