General Carburetor Jet Question
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General Carburetor Jet Question
In tuning my carburetor, I have found that for maximum RPM and vacuum, my mixture screws are only turned out about 1 full turn from all the way in to lean. Does that mean anything? Should I go with a smaller size jet? Would difference would I see economy wise or performance wise if I went with a smaller jet, and say, 2-1/2 full turns our from lean?
Also, for a 4-barrel carburetor, what would be the typical difference in jet sizes between the primary and secondaries? For example, if I am running a size 50 jet in the primaries, how much bigger would the secondary jet be from the primary jet?
Also, for a 4-barrel carburetor, what would be the typical difference in jet sizes between the primary and secondaries? For example, if I am running a size 50 jet in the primaries, how much bigger would the secondary jet be from the primary jet?
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Joined: Aug 2002
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Ideally you should be at 1.5 turns out...but that's close enough. With regards to jet sizes, we I would need alot more info such as max engine CFM, current carb cfm size & primary jet size
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Joined: Mar 2005
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The idle circuit is completely separate from the main circuit. Changing jets will have no affect on how the idle mix screws are set.
ON the secondaries, the only way to know for sure is with a wideband O2 sensor or a few trips down the drag strip. You can seat-of-the-pants guestimate by making a WOT run, changing to larger jets, make another WOT run and if it's faster repeat until it's not then go back one size.
ON the secondaries, the only way to know for sure is with a wideband O2 sensor or a few trips down the drag strip. You can seat-of-the-pants guestimate by making a WOT run, changing to larger jets, make another WOT run and if it's faster repeat until it's not then go back one size.
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