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Old 06-15-2006, 11:13 AM
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Carb adjustment needed?

Ok, so while my normal carb is apart, i have another Q~Jet from an '86 with a 350. it runs slightly rich in my vehicle, , and I think the reason why, is because that carb was tuned for a (Stock) dual exhaust (it was on a 1986 Chev Wrangler with a 350 dual factory exhaust.) when you hace a less restrictive exhaust, you need a richer mixture, is that correct, or am I mistaking???? I did plan to get a 3 in exhaust, will i need to tune the carb to prevent valve burning and get optimal performacne???? thanks for all the help

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Old 06-15-2006, 11:38 AM
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valves burn when the mixture is lean, if i were you and planned on keeping the q-jet i'd do some reading on the net , or buy a book on them, thats the best thing i ever did(for holley's of course).
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Old 06-15-2006, 11:41 AM
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I am not worried now about burnt valves, but if I were to get a magnaflow 3" exhaust, would I need a richer mixture??? how ca I tell when it is just right?
this will be on my soon to be rebuilt Q~Jet...
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Old 06-15-2006, 12:03 PM
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Is this a computer controlled q-jet, if not you may have to tune it a little richer, but if your building for power you'll want to go a little richer anyways.

What kind of car is this engine in?
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Old 06-15-2006, 06:50 PM
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re: carb adjustment needed

If you took a carb off a 350 and put it on a 305 you really need to lower your float level. they have different height levels for different ci engines. That is most likely why it's running rich. If you can adjust your air mixture screws with no or little change after dropping float level then you might be sucking air or ports are dirty. One neat little trick is to start engine,and from under hood rev motor to about 3000 rpm place your hand over top of carb to choke it out and when the engine almost stalls out remove hand and crack throttle open to about 5000rpm. do this a couple of times and this most of the time works on quadrapukes. check your plugs after idleing for a few minutes if they are tan in color your fine, if they are black and sooty your way to rich. if they are gray to white your to lean. if your not running between 450 and 500 hp 3 in. exhaust is to big. I feel you would be better off with 21/2 mandrell bent exhaust and x pipe, with this you will keep your torque. i hope this helped you in your quest!
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Old 06-19-2006, 11:08 AM
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carb is in a 305 chevy silverado...i meant 3 inch single, by the way. would a rich or lean mixture make the engine run hotter???
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