popping through the exhaust at 4500 rpm or so.. HELP!

[Zedyone_kenobi]

Okay, I will make these adjustments today. I understand what is going on now I think...

The Z therapy video has the float hung upside down and it is about .55" and level with the float top.. that may be due to the Gross jet he is using, which seems to have FAR less travel than my needle and seat. More on this later today...

[Zedyone_kenobi]

checked the floats this morning...They are right at exactly .55" when they first contact the seats +\- 0.010"

They pass the blow test as well, and shut off fuel right about the same time too.

Humm, another lead down the tubes.

I did notice that when I first looked at the front float, that the wrist pin was dislodged on one side. Now I do not know if I did that when I removed it or not, but it was the only thing noteworthy at all in inspecting the floats. If there are no more ideas, I will put them back on the car?

What torque goes on that 10 in lbs? It is not much?

[Zedyone_kenobi]

Screw it I am getting Mikunis! HAHAAH

[240260280z]

When I first measured H (14-15mm for early su's) it appeared that the aluminum swing arm which holds the float is parallel to the roof of the float bowl.

Now when I set the tang I just hold the assembly upside down and swing the float until it is parallel with the base and watch where the tang just touches the needle valve. This is a quick and dirty method.

The most accurate method is to:

1. bleed fuel from float bowl

2. remove domes

3. crank starter to run mechanical pump fuel (or electrical) and allow bowl to fill naturally

4. measure fuel depth in jet using "optical dip stick" (acrylic rod with two flush ends...when the rod is lowered and one end hits the fuel, the other end darkens)

5. repeat and adjust tang until fuel is ~10mm below the top of the bridge

[madkaw]

I'm at a loss myself. You might wait till your wideband is hooked up at this point.

I will be very interested in the outcome of this. I had a similar problem and it turned out to be those damn float bowl hoses. Looked great, felt great, but kinked up. Took a long time to identify the problem.

[Zedyone_kenobi]

It seems I am right with the first two methods Blue.

Nothing is really far from being 'spot on'. Everything appears to be as it should. I am going to blow out all the fuel lines and put everything back together. Then I will get some clear tubing and try to mark where the float comes up on the car. But all of this is just for ****s and giggles until I get my wideband installed this week! Should be here tomorrow or wednesday.

[Zedyone_kenobi]

Just wanted to thank all of you again for the help. I am usually pretty savy with carbs. Was a bit of a Holley guru in my V8 days. and these SU's seem just wonderfully simple, but often the most complex things are the simplest. For the life of me, though, everything I do seems to result in ziltch. They are so clean you could eat off of them. This is truly a strange case.

After I get the wideband stuff, it will at least point me in a direction...lean or rich.. well lets hope so.

[motorman7]

Fuel filter? Finally got the car running great, but not sure if it is the same issue that Zedyone is dealing with. Changed out the fuel filter (I think that was the main issue), moved my 280ZX dizzy to 20 BTDC, Vacuum hose not attached, and drilled five 1” holes in the underside of my air cleaner housing (not sure if that was necessary but I had been wanting to do that). Seemed like it ran better with the air cleaner housing off. No popping at all now. It revs and runs nicely at over 6K rpm.

Testing this can be dangerous. I am doing over 90MPH in 3rd gear at 5.5K. Fortunately traffic on freeway was light today. Doing around 60 MPH at 6.5k in second. Was not paying careful attention on one of these runs and locked up wheels when light turned red. No accident, but lots of smoking rubber. No ABS on this vehicle. Anyway, glad to be back to normal.

On a side note, I do have to say, I rarely take my car over 4K RPM. My typical shift point is 3K. Nice to know that it will do it, but can’t say it is very useful

Rich

[5thhorsemann]

On a side note, I do have to say, I rarely take my car over 4K RPM. My typical shift point is 3K. Nice to know that it will do it, but can’t say it is very useful

Rich

It will be very usefull when you need it. Kind of like my H&K USP .45 ACP, I haven't ever had to use it, but it sure feels good knowing it's there if I ever need it.

[Zedyone_kenobi]

H&K,

Very nice...

[Zedyone_kenobi]

UPDATE:

5pm this evening I get all the carbs back together and fill them with a lighter oil. I used Marvel Mystery oil per somebodies suggestion. Car now pops and sputters at any throttle change above 2200 rpm. It is leaning out way to fast as that piston rises so much faster. Definitely a step in the wrong direction!

I will clean out the carbs again and fill them with straight 20 wt oil. I have no idea what the SU oil is that I bought. I only know the marvel mystery oil made the plunger FAR easier to push up.

[madkaw]

Trans fluid works also.