If you get a different cam you'll need a re-tune. Along with bigger heads. Im not sure how you would go about leaning it out with a tune.

 

Wait, you rebuilt a motor cause it was running rich?

Sounds like you need a new tuner... To make it run more lean, you tune it. Simple and there really is no other valid way to do it.

 

It was buikt and tuned. Then it had an oil leak so i had it redone. New bearings rings gaskets. One spring went bad in the head for the valve so i got all new springs. Its a 93 so u have to pull the entire computer and blank the chip then reprogram it. Its not cheap. Thad a problem when he was tunning it and after he went as far as he could i raced it at the track a few times but was haveing idle issues. Pulled the fuel pump out because pressure was going crazy. Found a blown fuel line. Replaced it. But need to dial back fuel a touch but cant find the tunner that did it. So a new hard to find because of the style it is would be another 500 bucks to run it on their set up. Like i say its running 13 to 14 on air fuel dipping to 12 on a meter of 10 to 20. Didnt know if there was a slight change i could do to change it.

 

12 is 5.5% rich, 13 is 2.3% lean and 14 is 10% lean. The AFR will hit those numbers depending on various engine load conditions. Is the 13-14 at idle constant ? You had a problem that was fixed with O2's a while back that indicates the ECM is running 'closed loop' and it is constantly altering AFR to hold 12.7. Whatever you do to the engine (change cam, etc) the ECM will always try to hold 12.7 by adding or pulling up to 15-20% or more fuel. During those abnormally high AFR corrections the engine usually runs crappy w/idle, acceleration of idle problems. That's why tuning (timing, VE and TBS) after a cam is required. The only way around ECM AFR control other than 12.7 is a 'closed loop' tune. My guess is either: 1 - if your WB is accurate then one of your O2's is reading 3-11% rich due to bad O2 in one bank and it's pulling 3-11% fuel in error. -OR- 2 - the WB may be reading a tad lean at certain conditions. Is the the 12 during acceleration, deceleration or cruising ?