Re: Timing Effect on Oxygen Content

On Sat, 27 Jan 2007 18:57:02 -0600, "James Drinkwater"


Timing should have little effect on oxygen content. The oxygen content is determined by the fuel - air ratio going into the cylinders and that is controlled by the carb. Maybe re-jet it to be sure you have stock jets, then start adjusting the mixture screws.
Tom S.
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If the carb was used on any sort of a "drag" motor... then it probably has the wrong power valve in it (or the power valve is damaged); and the power valve is opening during part throttle cruise. There's a description of how the power valve works here: http://www.chevyhiperformance.com/techarticles/74058_carburetor_valve_problems /
"See if this description sounds familiar: Your Holley-carbureted street car idles terribly, has taken to fouling spark plugs every week or so, the gas mileage absolutely sucks, and there's an ominous black cloud swirling from your exhaust."
I think you're supposed to select a power valve that's rated about 2" HG lower than whatever your part throttle cruising vacuum reading is: http://www.chevyhiperformance.com/techarticles/74058_carburetor_valve_problems/index1.html
wrote:

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The engine's brand new. Took my sweet time and did it right, so, compressions great. I adjusted the floats over and over to make sure they're good. Even swapped the needle/seats. Pulled the carb bowls, cleaned 'em out, set the floats at baseline to fine tune afterward again. Jets all labeled as stock (but we've already said it won't hurt to swap just to be extra-sure). Visually inspected the power valve, marked as stock 6.5", with no apparent rupture & held vacuum. Ya know what? I'm a little tired of talking dumb. I'm just gonna swap jets and power valve like I know I should've done in the first place! Drink

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