360 gas mileage tips? - Page 2 - JeepForum.com
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post #16 of 23 Old 09-07-2009, 06:54 PM
80cj
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Well I tuned the carb down a bit and I got about 12 on a 400 mile round trip. Its still running rich though I can smell alot of gas. Think I might put a smaller carb on there? Anyone running the Holley 500 cfm 2 barrel carb?
Maybe rejetting would help. Look at your plugs. If they're black and sooty, the mixture is too rich. Lean out until you get a nice tan color.

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post #17 of 23 Old 09-07-2009, 07:41 PM
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how long do you have to run the jeep to wait for the plugs to turn colors
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post #18 of 23 Old 09-07-2009, 08:23 PM Thread Starter
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the whole inside of the carb is all black and sooty.
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post #19 of 23 Old 09-08-2009, 10:03 AM
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CHECK YOUR POWER VALVE!!! These are notorious for causing this situation. Basically, if it is blown it will throw you into a rich mode. They are around $20 for a good single stage (according to ponycarbs.com the single is better than the dual stage). Takes 20-minutes or so to replace...
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post #20 of 23 Old 09-08-2009, 10:38 AM
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Why not put a Vacuum Gauge on the engine and drive it so the vacuum remains as high as possible. It also may show a few problems you may not have noticed yet. As twmattox mentions, it might show you why the power valve is opening up to early costing you gas.

If the Holley 500 is a peripheral port 2 bbl then you're better off with a 4 bbl. The 500 CFM is a great carb for WOT But it's not that good for economy.

You know whether you have 4, 6 or 8 Cylinders it's only going to take so much gas to keep you running at a certain velocity. An 8 may be a little heavier costing you some mileage but just because it's a V8 doesn't mean you should be getting 1/2 the mileage I'm getting.

Get a vacuum gauge, it will help.
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post #21 of 23 Old 09-08-2009, 12:57 PM
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how long do you have to run the jeep to wait for the plugs to turn colors
I used to run 5 or 6 miles of normal driving.
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post #22 of 23 Old 09-09-2009, 10:35 PM Thread Starter
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Power valve? Im not totally sure what you guys are talking about. Its a regular edelbrock 4 bbl, there is not alot to it, could you guys elaborate a little im not very mechanically inclined.
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post #23 of 23 Old 01-10-2010, 09:37 PM
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i think im doing pretty darn bad i have a 360 4bbl proformer intake hei t176 flowmasters no cats 35s 4:10s im geting around 5mpg wtf guys
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