8.5:1 340 slightly perked up, cam, headers, RPM intake, holley 750 dbl pump. seems to be a bit rich going by tailpipe odor and appearance, plugs are on the brown side not black but not white. Am I going to help or hurt performance by going more lean? At the track the car ET's better as the air temp cools, perhaps this is typical, but the motor does appear to be rich going by observation noted above. Tried a 650cfm holley and it seriously hurt botton and mid range, put 750 back on, runs better but seems a bit rich, so should i tweak on the 750 or 650? Another thing to note, is that at the Classics I started out doing my burnout with secondaries and ran 13.50s. I tried doing my burnout with primaries only and dropped to 13.20s...all of that gained in the 60ft and 330. Right now my jetting is 73 primary and 76 secondary. I have been told my numerous people that the 750 is too much, but I have tried a really good Holley 650 and a 600 Eddy and even after some tuning neither one would come close to the 750. If you need more info, just ask. Any input would be greatly appreciated.

Thanks

The true way to see if its rich is to shut down at
the end of the 1/4 mile and pull a plug or two but
your running rich now... lean it down. The difference
in your burnout could be just over heating your tires.
A nice 750dp is great on a 340... and you have already
seen that. Keep jetting till you see the highest MPH

Rich @ idle can be adjusted out but for power you need to know whats going on by shutting down after a wot pass before you go back to idle

With 8.5 to 1 compression you are going to have a hard tiem hurting the motor when you lean it down, as long as you let up on the throttle if it starts to miss, pop or lay over at WOT. Try leaning the carb down 2 jet sizes at a time at the track until the MPH reaches a peak and starts to slow down. Once it starts to slow down go back up to where it ran its fastest MPH and try one jet size each way from there, keep the jetting at the best MPH. If you can't fatten the jetting up enough to slow the MPH down in the 1/4 mile fix the fuel system so it will