Carburetor tuning

[Frankensteinz2]

Hey guys,

Okay I have my z running now, however im havin troubles tuning it.

I guess the best place to start is that i have my adjustment nuts turned all the ways anticlockwise if you are lookin down towards the ground, as this is the only way i can get it to idle. When i went to put my air flow sychronizer on the front carb, the engine reved real high, but it does not on the back carb. On the front carb i have loosened the idle screw as much as possible and it still does this. What could be the cause, am i doing something wrong? I adjusted my floats to 14mm the best i could, and filled my dome tops with a cap of ATF each.

I should mention i just got her running after rebuild. I was going to tune the carbs before i use the timing light to set the car to the exact timing degree. Is this the right order?

One more question while im on the topic. What should the timing be set at?

Thanks All

Frankie

PS Its nice to hear a Z again!!

[ChrisZ]

Frankie, i could write you a write up, buy i'm not in to spending a shite load of time on that now, so i will advise you to use the search function, this has been covered many times and you will find a "how to " if you search.

Chris

[Frankensteinz2]

Oh trust me i have, and from what i have read im gonna go with lowering the floats as i think im getting to much gas.

Ill give it a shot

Frankie

[doradox]

Dwell (or point gap) then timing, valve adjust (could swap order with dwell/timing), carbs last.

Steve

[Bruce Palmer]

Have you got the JUST SUs DVD? If not, save everyone a whole lot of time and get it.

Two initial things to check for before ripping into float settings. Make sure the center linkage captures the linkage on both carbs and 2 with the choke lever released make sure there is slack in the cables whaere they attach to the carb linkages.

[Frankensteinz2]

Okay, I have to solve this car problem before i can time because i can't get them to idle down to 600 or 700

Now the more I read I think i might need to take the carbs off to check to see if one of the butterflies is stuck open

Thanks for the order Doradox, I will do the tuning after i set the timing

[beandip]

Okay, I have to solve this car problem before i can time because i can't get them to idle down to 600 or 700

Now the more I read I think i might need to take the carbs off to check to see if one of the butterflies is stuck open

Thanks for the order Doradox, I will do the tuning after i set the timing

First off where is no where?? If you have checked that you have all or any vacuum lines connected correctly. SUs ?? Then looking down from the top the mixture /nozzle adjustment under the carb is turned from the counter clockwise stop. Clockwise 2 1/2 turns. The engine should fire and run reasonably. The air mixture must be balanced with the proper tool. Set the timing at around 6* BFTDC to start. You haven't stated said what engine or ignition or what carbs you are working with. I looked out the window and couldn't tell from here. More info would help.

[Frankensteinz2]

Im from Fort Wayne, Indiana and Im workin on a 72 240z w su's 3 screw carbs

[Frankensteinz2]

Im not sure what ignition it is, I assume points but I took a picture of it to be sure.

Vaccum hoses are all connected, and i have set timing at 6 degrees BTDC @ about a 1000 or so

[Arne]

Looks like a ZX E12-80 electronic ignition to me.

[Zs-ondabrain]

That's an electronic ignition, most likely an E12-80 out of a 280ZX. You should be able to adjust the carbs to no air at all and it dies. Basically, you're missing something.

I find that most people miss the ballance screw on the linkage that connects the 2 carbs. Using the picture below, loosen #1 till it's NOT touching at all, that's your fast idle screw, used for tuning carbs at around 3000 RPM. Make sure your return springs are snug and pulling the throttle closed. If they are loose, the car will idle fast.

Loosen #2, 3 and 4. #2 is the ballance screw I spoke of. It ballances the carbs so the linkage operates both carbs at the same time. Loosen it until both carbs work at the exact same time with every push of the throttle.

Loosen #3 and 4 then slowly turn them back in until the just touch the idle plate, then give them about 3/4 more turn (clockwise). Then start fine tuning with your flow meter.

ALSO, make sure that Vaccum pot that is on the ballance tube, attached to the front carb, is not holding the carb open as well. Loosen that.

If I'm wrong, Bruce or someone else will let me and you know.

Dave

Edited September 4, 2009 by Zs-ondabrain

[Frankensteinz2]

I assume number 3 is the throttle adjustment screw rear carb, and i think number 4 is wrong, i think that screw is for the vacuum pot, correct? the throttle adjustment screw is behind that, (not visable in the picture) correct me if im wrong

I am taking the carbs off now and readjusting the throttle adjustment screws as you said in your post