Rough Idle (video)

[vling]

just got a coil and rotor. cap and wires and points are coming in tomorow. will it damage the new parts if i run it with mixed with the old wires/cap points

Thanks for sticking with me weasel

Edited August 5, 2009 by vling

[Unkle]

Loose the points and literally screw in an optical/magnetic set up.

Takes 1/2 an hour start to finish, no more gapping and guessing!

[vling]

Unkle - I'm already feeling the money being sucked out of me haha. Maybe later down the road though. I just want to get it running normally for now.

Ok so..this afternoon put in the new coil and rotor just to see if they'd make any difference. Nope. I then took apart the carbs, and couldn't find anything particularly uneven between the two, except for a tiny speck of dirt on the front (bad) carb jet. Also there were no gaskets between the dome and body of the carb :/. Anyway I cleaned both up with carb cleaner, reassembled, put in 20w50 damper oil. Reset the mixture nut to 1 turn out on both, started again, and the engine started racing to 3-4k. Ok, so I backed off the throttle, idle, and balance screws so they had no tension. The car was running differently. It sounds and feels alot smoother now at idle. No shaking like before. I thought ok all 6 must be firing, so I went to do the plug removal test, and now, 123 are firing, 456 are not! This is the exact opposite of what it was doing right before I cleaned the carbs. So now glad because I guess that rules out some horrible timing/valvetrain problem, and hopefully it's just the two carbs being way out of sync that is causing these problems.

I measured both carb's needle lengths (identical). Jets looked identical. I'm not sure what could be causing them to be so way off, or what would make them switch inversely like that all of a sudden.

Also the car does not want to idle very low anymore. It's at 1200rpm with both mixture nuts out 1 turn. From my understanding I should be closing in the nut (lean) to get it to idle lower? My throttle, balance, fast idle and choke are all completely slack, is there anything else I should be adjusting?

Thanks for bearing with me guys

[Weasel73240Z]

If your floats are set at the right level, you should be somewhere around 2-1/2 turns out. You may have a fuel bowl/float level issue if it runs best with them 1 turn out. If you take off the domes and look into the carb, you should see fuel about 1/16 or 1/8 below the top of the fuel opening. Thats one easy way to check float level w/o removing the float covers, which can be a be-atch. Just be careful not to let the piston (with needle) fall out of the dome when you do it, or the needle will get trashed. Slowly lift the dome after you take out the 3 screws about 1", and you'll see the side of the piston, pick them up as one piece.

The FSM says the float should be around 1/2" from the top of the float cover when you invert it. Measure as soon as the float arm touches the pin to shut off the fuel. My car runs better when the measurement is around 3/8".

BTW, you don't slow down the idle with the mixture screws. You reduce idle speed with the brass screws next to the domes, near where the linkage goes through the carbs body. The mixture screws are just for getting the A/F mixture right.

Before you spend any more on parts, get the ZTherapy video "Just SU's", it'll teach you what you need to know to tune and balance these carbs. It'll be $20 well spent, trust me.

Get on the rest of the ignition parts and report back. You'll get it, it just takes some digging sometimes.

[vling]

Ahh the sweet sound of victory!!

all 6 glorious cylinders firing!!

The problem was

1. rear carb float level was wrong! (although that is the first thing I adjusted when I got the car, mustve got knocked off adjustment when I was installing it)

the rear float needle was also a tiny bit uncooperative, recleaned it. replaced the fuel filter again since it was getting clogged with rust particles left over from the old lines.

But the main problem here was that I wansn't adjusting the two throttle screws at all. For some reason I thought the only thing I was supposed to be touching was the mixture adjustment nuts. THANK YOU WEASEL for clarifying that.

Ahh! I can sleep easy now...

Ok well on to the next issues. When I lift the rear carb piston slightly, the engine stumbles, which means I should enrichen the mixture (turn out) right? The problem is that I am turned out all the way to the stopper. Now should I try to loosen the stopper, or adjust my float again, and if it's the float, should I make the "H" distance shorter or longer? What else can I do to enrichen the mixture further?

Thanks for all the help guys, especially Weasel thank you thank you!!

[Weasel73240Z]

Ok well on to the next issues. When I lift the rear carb piston slightly, the engine stumbles, which means I should enrichen the mixture (turn out) right? The problem is that I am turned out all the way to the stopper. Now should I try to loosen the stopper, or adjust my float again, and if it's the float, should I make the "H" distance shorter or longer? What else can I do to enrichen the mixture further?

Thanks for all the help guys, especially Weasel thank you thank you!!

If you are turned the A/F mixture screws all the way out and you still aren't rich enough, the float bowl (fuel level) is probably still too low. Take off the float cover, and bend the arm on the float so that the float stops higher. Make small adjustments, maybe 1/8" at a time. The big pain in the arse is the fuel bowl gaskets usually get trashed when you take off the fuel bowls. If you are turned all the way out and still not rich enough, I'd bring the float up about 1/8" - 3/16" or so and try again. You're right there, a few more tweaks and it'll be screaming.

Glad to hear you got it this far. These carbs are great when they are dialed in, but they do take some fine adjustment to get running perfect. :classic:

[vling]

If you are turned the A/F mixture screws all the way out and you still aren't rich enough, the float bowl (fuel level) is probably still too low. Take off the float cover, and bend the arm on the float so that the float stops higher. Make small adjustments, maybe 1/8" at a time. The big pain in the arse is the fuel bowl gaskets usually get trashed when you take off the fuel bowls. If you are turned all the way out and still not rich enough, I'd bring the float up about 1/8" - 3/16" or so and try again. You're right there, a few more tweaks and it'll be screaming.

Glad to hear you got it this far. These carbs are great when they are dialed in, but they do take some fine adjustment to get running perfect. :classic:

Adjusted the floats today, and now they are so far up that they don't even close the valve fully. I am still running lean (lift carb piston, engine stumbles means lean right?)

Maybe the float valves are sticking?? I dunno but adjusting the floats doesn't seem to affect the A/F mixture

My rear cab gasket was MIA when I took off the cover, (rear is the one that is running lean) Front carb has an intact gasket. New float gaskets coming in from Ztherapy soon anyway.

rear carb float adjustment getting out of hand :/

new plugs are fouled again (doesn't smell like fuel, and is drier than the last set)

Edited August 8, 2009 by vling

[yetterben]

the plugs are carbon fouled you are too rich. it could be stumbling do to the fact when you lift the piston you are dumping even more fuel in there boggin it down. Turn them in all the way and back out 2 or 2 1/2 I do 2 and work from there but i am only 600 feet above sea level. What i do when i tune is leave 4 old plugs in that are still good and only put 2 new ones in so i am not trashing whole sets at a time. YOu are barely supposed to lift that piston too. Like a **** hair. Anymore will give false results

Edited August 8, 2009 by yetterben

[vling]

$^!#, thanks for the tips.

Should I reset the floats to fsm get new plugs and try again?

[Unkle]

A hotter spark would help as well , but you're nearly there it seems !

Like the pics, a thousand words .

[vling]

Well I think I've got it running at a decent state now. The odd thing is that all the plugs are carbon fouled, making be believe it is running rich, yet when I lift the piston ever so slightly, the engine stumbles, which is supposed to mean it's running lean?

ehh whatever. Today I got a thrust welded muffler, put it on backwards, because it won't really fit the other way haha (does that screw up the muffling?). It's quieted to a bearable level, but still pretty loud. I did a hot compression test.

dry

1 - 175

2 - 175

3 - 170

4 - 170

5 - 175

6 - 175

wet

1 - 175

2 - 175

3 - 175

4 - 175

5 - 175

6 - 180

Oh and now all the doors lock!! woohoo! (driver door was sagging)