so i have an 85 z24 720 kc

and as funny as this may sound the truck runs best when the timing is at 14*btdc california emissions require it to be within 3* of 0.

i set it at three btdc and its undrivable i set the idle at 900rpm and messed with the air/fuel for like 4 hours and could not make it run right. i have new plugs and wires, cleaned distributor contacts, checked all the vacuum lines throughly, and still only runs right at about 14 deg advanced.

what am i missing or doing wrong? does any one know the magical air/fuel mixture (ie. all in 1 1/2 turn out)

thank you

oops forgot to say what it was doing,,,,,,under load it will not accelerate it just sputters hard and stalls out. what im having a hard time figuring is why it would run so flawless at 14 off?

possible vacuum advance problem? or could it be im getting no vacuum in my thermal vacuum valve?

wait... so they actually hook a timing light up to it to check the numbers? If not, just tell them its within range... seems odd, but i guess cali really is insane

i suck with the whole passing emissions thing man... can't really help ya

pejsa s-13 wrote: or could it be im getting no vacuum in my thermal vacuum valve?

that's a possibility i suppose... but can't really say for sure... that maze of vac lines as you already know is near unpredictable

yea they hook the truck up to a scope that measure everything man if the idles to high fail to low fail visual fail gas cap fail its nuts.........

and i would have left it at 14 but my nitrogen oxide readings are around 6000 when the legal limit is 1100 or so. so im pretty effed i guess

This happened with a z20 rebuild I did about 8 years ago. When the drive for the oil pump was installed it went in the wrong position, so the timing was off. I removed the dizzy and the oil pump pulled the drive rod and turned it 1 tooth. Cant remember which direction now but it took me about 2 hours adjusting and readjusting but I got it right. You may need to do the same.

damn that doesnt sound fun

do you have to unplug the vaccum advance when you set the timing?

when was the last time you rebuilt your carb? It may be that you're getting extra air through a tired carb...

pejsa s-13 wrote:do you have to unplug the vaccum advance when you set the timing?

Not necessarily. But its the better way to do it.

thanks and as far as i know the carb has never been touched stock hitatchi

when I removed the front cover on my z24, It required removal of the oil pump. During reassembly, I inadvertently ( i am an idiot, btw) reinstalled the tooth edge 180 degrees out. It ran similar to what you say, but would not run properly unless it was way advanced. Also some guy who rebuilds these napz motors told me you can advance your ignition coils to get more power. I will ask him about it again, since it could be something else that would screw with emissions crap.

You will need to disconnect the vaccum advance to time it. Is your rig setup with the California emissions. If so I can give you in depth instructions for the ajustments from my FSM.