On 20/11/2017 at 2:23 PM, Stanley said:

Note that the pressure and flow in the FSM  are tested by attaching gauge to the fuel pump outlet (return line out of the loop). So in a system with a return line, pressure and flow should be somewhat less. I'm not using a return line, getting 3.9 to 4.1 psi. Never had an overflow (with the floats at stock setting). It varies depending on whether the float bowl valves are open or closed. My gauge only goes from 0 to 5 psi so it's easy to see the variations. The gauge goes nuts when the car starts running out of gas.

Well this is the airtex 8012s electric fuel pump installed in my 72 240z next to the gas tank. Could the metal filter be clogged ans thus avoiding free flow to the carbs? The problem is clearly at idle. The guys at the paint shop accidentally painted the pump black while throwing paint to the suspension parts.

Edited November 23, 20177 yr by jalexquijano

I think 5 to 6 psi would be OK if you're running a return line.

On ‎11‎/‎23‎/‎2017 at 12:20 AM, Stanley said:

I think 5 to 6 psi would be OK if you're running a return line.

Yes, I run the return line. I noticed when I replaced all the rubber fuel lines that the exit of the fuel rail on the motor is restricted which I'm guessing is to give some back pressure in the system.

Good idea to set up lines from float bowl vents to clear plastic catch cans to make sure there's no overflow. The catch cans should be located where fuel will go on the ground if they overflow instead of pooling somewhere (like stock air cleaner) or going on the exhaust pipe.

I had the floats set slightly higher than stock for a while. Got about 1/2 ounce total overflow over a year.

With the new airtex 8012s pump the psi raised to 4psi and nl overflow. Response got better but at 2.70 turns clockwise at the fuel mixture knobs of both su roundtop carbs. I even took a picture of the plugs for your opinion. Am i still too lean?

 Yeah, too lean. The color should be light to medium tan, not white.

Yes i know but if i go too rich i would then have a problem when the car is as idle as the plugs start the foul getting sooty black which causes the car to hesitate under traffic situations with a tendency to stall. I am using a cheap automatic transmission fluid for my su carbs. My problem is always at idle.

 Go to 2.75 and check the plugs again after a few days. Small incremental changes. Try to keep the drive the same between plug checks. In other words, if the plug readings have been with, say, 1/4 traffic and 3/4 highway miles, try to keep the percentages the same. Don't read the plugs after idling in traffic one time and after highway miles the next. Try heavier wt. oil in the carbs and see if it helps throttle response. Heavier oil shouldn't affect the idle.

Edited November 29, 20177 yr by Mark Maras

Is it normal for plugs to get sooty black during long idle traffic time?

No

How do you avoid this? Trial and error?

 You don't avoid it, it's part of the tuning process. I would suggest that while you're idling in traffic, keep the RPM's up at a happy idle, maybe around 1500 RPM's or a little more. Or, if the engine starts easily when warm, shut it off when you have to sit and idle. See if that will keep the plugs from fouling. The needles, springs, float level, could cause the sooty plugs at idle. I think you had SM needles, what color springs are you running? I know you set the floats but you wouldn't be the first person to have to go back in and tweak them a bit. I won't be convinced that they're right until you pull the domes and pistons and tell me what the fuel height in the jet is at 2 1/2 turns down.