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Old 04-09-2012, 02:51 PM   #1
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Default A/F ratio and carburetors.

What numbers do you guys like to see?

My truck seems to like 11.3 all the way across the board. The motor is a built 306 SBF with a Holley ultra 650cfm DP carburetor. About 16* initial timing. It'll rip the tires off of it shifting all the way up through third gear.

If I bump the ratio closer to the desireable 14.7 it just feels really sluggish and has poor throttle response.
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Old 04-09-2012, 03:00 PM   #2
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Might be hard to get any input since I'm one of the few carb'd guys on here.
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Old 04-10-2012, 02:10 AM   #3
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14.7 is the desired normal driving target, but WOT I believe it computes to around 12.7

For some reason mine goes rich 11.8-12.1, even though it was dialed in at 12.7.. Not sure about carb'd setup's but I would think essentially it would be around the same My truck runs well though, even though the injectors are beyond maxed
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Old 04-10-2012, 04:30 AM   #4
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14.7 with a properly working EGR system is normal for emissions/fuel economy.

If you engine does not have an EGR, 11.5 to 13.0 is a typical range. 13.0 is about as lean as you want to get on a steady speed. Mine runs at around 12.3 and seems to work great. alot of the older (pre-1974) like 11.7 to 12.2 for peak power.

Many newer fuel injected cars are setup for 12.7 only at wide open throttle. This can vary because at wide open throttle the computer does not continually adjust the ratio.

Do not try and run the leaner ratio's without an EGR, You can burn pistons and warp heads with the higher head temps.
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