Almost there, 1 question

[Art@NissanSport]

I have adjusted the valves, adjusted for timing chain stretch. Car seems to run fine when stationary.

I have balanced the carbs and I'm now trying to adjust the fuel mixture.

I have started at 2 1/2 turns out.

My problem is that if I rev the engine slow to medium it seems to rev up fine. If I rev it fast from idle it backfires out of the front SU. If it does in the back SU, it is hardly noticable. I've tried adjusting by turning quarter turns in one direction and if it didn't work I went the other way. I can't seem to find a happy medium.

My question is: What am I missing. I have the ZTherapy video but it doesn't really disscuss troubleshooting.

[Bruce Palmer]

Art,

Sounds to me like you're a tad lean causing that carb to spit back. Run that nozzel down in increments and see if it doesn't stop doing it. If you get where it's huffing black out the tail pipe and sounding real blubbery, you've gone too far.

[Art@NissanSport]

Bruce no matter what direction (up or down) I go it still backfires if I rev it fast. A slow rev seems to be ok and then once I get to a higher rmp slowly I can rev it fast and it works much better.

At one point I had it completely closed and it didn't backfire, it idled slower and I'm sure that is not where the setting should be. The more I opened it up the more it backfired.

I have no idea how it will react under load.

[240ZX]

Art,

You didn't mention what year Z you have.....! Another thought to consider is the distributor....as in it's not advancing properly. As many know, if you have upgraded to a ZX dizzy, the advance mechanism goes bad and does not advance properly. Just some food for thought!

Tom

[turbo 260]

Art,

How is the oil in the carbs? If one (i would guess the front) has more oil in it (or a different kind) it will respond slower, thus leaning out the front carb. lift both pistons by hand al the way to the top. do they feel about the same? Let them drop from the top, they should clunck at the same time. You could also have the alingment of the domes off. I always move the piston up and down while tightening the screws on the domes, seems to work.

By the way, are you coming to Daytona? I still owe you a ride in the 260!

Jim

[Art@NissanSport]

I've worked on the oil trying different types and I don't think it is the problem.

I was on the phone with Steve Epperly for quite a while today and he told/showed me a better way to adjust the floats. Combined with the fuel adjustment it seems to be running a lot better. Still a little rough but without the cough from the front carb.

I also have to work out some timing issues. might be a tooth out of wack on the distributor and will probably pull the oil pump to make the adjustment. Not looking forward to it but such is life. Seems that the car runs best at about 17 degrees. If I go any lower, like 10 degrees the car wants to stall.

Doesn't seem right when the dizzy is turned all the way to one side when it should be more in the middle. I've tried two different dizzys with the same results so I don't think it's a vacuum problem. Although I will test for leaks around the manifold and carbs tomorrow.

Yes, I will be in Daytona. I'm trying to see if I can get to Jim Fredericks house to see his stable of Z's. I fly in on Saturday, so maybe Sunday. I'll see.

[turbo 260]

Art,

I'm about 10 minutes from Jimbos. I'll be leaving early Saturday to head over to Daytona. Are you flying into Tampa?

Jim