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Originally Posted by 67ragtp
Jody,
should the typical a/f ratios be close to 14.7 or above 13.5 for mild cruising such as back roads and highway driving? I know what you mean about not getting caught up on a number, its nice to hear what kind of numbers you guys have seen in your experiances, my application is a normally asperated 427 sb with a 1300 cfm 4150 style throttlebody, nothing extreme 500hp/500ftlbs. Any advice is appreciated, thanks guys.
Rich
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cruise areas I can almost always get pretty lean, 15:1 or beyond. There's no load and you'll pick up some mileage. I shoot for 12.8 to 13.2:1 WOT on a naturally aspirated combo. Some like to be 13:1 or so and others pick up being a bit richer at 12.8 or so.
At idle the individual runner setups I've tuned always wanted to be around 13:1; wouldn't idle well any leaner, yet they'd cruise much leaner. The Mule didn't like anything leaner than 13.5 to 13.8:1, you could hear the engine change when it got leaner, so that's where we left it. Most my other solid roller setups have idles at 14:1 or leaner, just depends. You can hear the engine gettting "unhappy" when you start to lean it or richen it too much at idle and light cruise, so you'll need to experiment where to set it at.
Jody