Air/Fuel Ratio VS. Horsepower
 

Let's say you have a Pontiac 455 that's built for 500 HP. Engine runs great, but
tail pipes are soot black. How much Horsepower could one be off because of A/F Ratio?
(Rochester Q-Jet for Carb.)

Thanks,
David

You can lose as much as 10% depending on how rich it is. But black soot on the tailpipes doesn't mean it's necessarily over-rich under wot. You need to read the spark plugs, monitor a/f ratios and/or exhaust gas temps.

Could be the power spring for the metering rods isn't right and rich at idle

Are you loosing any oil? Does the PCV valve have oil in it?


I had the same problem with my 350. Wound up having bad machine work, oval cyclinder walls.