Too Lean?

[doodles526]

So I've had my 260 for a while now, and when I tuned the carbs in the past I've used a unisyn to balance and done the rest by ear. But this week I looked up more advanced ways of tuning like using a vacuum guage and using the tabs on the bottom of the carb to lift the piston.(I also tried using a colorTune but it turned out to be the most worthless thing I have ever bought, my engine was almost stalling on the road when it told me I was in the "bunson blue perfection zone")

After using all these tests(besides the ridiculous colorTune) they all imply that I am too lean no matter what I do. Float bowls as rich as they will go and mixture knobs all the down. The car runs fine as just a cruiser, but step on it and it sounds like a dying moose. Beautiful idle and throttle response without load though

I don't know if this would make a difference with tuning, but when I bought the 260 it came with a 280zx L28 with an earlier intake(I think from a 240) and 4 screw SU's. Any ideas?

And sorry, I didn't realize there was a dedicated SU section here so I already posted this on the Engine section of the site, so here it is in the right spot

[Zforce]

When you set your mixture using the color tune that was at idle so it probably was set perfectly for idle not as you are driving down the road. If you are in fact leaning out at speed many things can cause that. start looking at the fuel system as a hole starting from the fuel tank moving forward. The engine should be the last thing you mess with. If you start screwing with the engine you will most likley mess things up worse than before you started, by begining at the back of the car you will probably find the problem before ever touching the engine. Most of the time clogged fuel lines and filters are the problem especially the fuel lines, what do need to make a fire ? air,heat and FUEL good luck.

[Travel'n Man]

I'm confused on why you would use a Unisyn to balance the carbs but not use it for the most detailed part (not logical). There are tons of info on this site for Hitachi carbs - I would read - study - gather some information - and make a sound educated decision on how to correct your problem. Even better, there is a great DVD out that can assist you with step by step instructions on tuning - rebuilding - float adjustment -the whole nine yards............the search feature is a powerful tool. Keep us posted on your results!