Well, I just got my colortune in the mail and it confirms exactly what I already knew. I am rich, even with the adjustment knob all the way up on the front carb. Oh, this is on 3 screw 72 round tops

Last night I checked the valve lash while hot and only had to adjust a couple of valves from the cold setting. The float seems to be set right at 23 mm from the bottom of the lid. I also synced them at 1500 and 700 rpm.

This evening I tried tuning with the gunson and got the rear carb right where I want it. Even the lift the pin method is showing good on it.

The front carb is another story. Even though it is rich I can only get it to run good at 1.5 - 2 turns out. I can't get the color to hit blue no matter how tight i get the screw. However, fully tightened the car will barely get out of its own way and will lean pop. At eithet setting opening the throttle will net a blue flame and a quick opening will flash yellow.

Does this mean my needle/nozzle is toast? Would it make more since to fiddle with my floats again and lower the level a mm or so?

Edited September 7, 201014 yr by hogie

The colortune isn't the final word on whether the carbs are just right. It's purpose is to get you into the ballpark. In the end, it takes just the right about of voodoo to get the SU's right. It's a subjective call, not a value that can be measured (unless you have a dyno, that it).

Im using a wideband o2 sensor. In my experience I have found that if you adjusted the mixture on an SU to be correct at idle you will most likely find that your car is too lean under a load at rpm. At least thats what I have found. My car runs best when the idle mixture is rich(about 10.3:1 air fuel ratio). Under load at higer RPMs the mixture settles in at about 12.5:1 to 13:1

Edited September 20, 201014 yr by whamo