[Son of Magni]

Ok, the service manual says keep turning the mixture adjusters to get the highest idle with good ignition. This pretty hard to do because the speed changes so little when you turn the adjusters. I've heard of another method which is you lift the carb pistons 1/8 inch, the engine should race for a second or so then:

If it stalls it's too lean

If it stays high it's too rich

If it drops back to a rough idle it's perfect

First question - Is this correct?
Second - How many turns up from the stops is normal?
Third - Which way (up or down) is richer?

I keep trying to adjust mine but no matter where I set it, it stalls when I lift the pistons. I've already balanced the carbs and its sitting at about 750 rpm. Also it has Austin Healy pistons and oversize jets.

 

[mizhele]

hello on my 240z before i got my color tune i would do the following..turn both adjusting nuts all the way up till hit the top or bottom out on the base of the carb..then turn 2-2 1/2 turns clock wise..pulling away from the carb downword..see how the engine runs ..blip the gas a couple times and let it idle...if it runs rough then turn the adjusting screws equally counter clock wise ( back up towrd carb) to lean them out.a bit, untill you get a nice smooth idle...go for a ride..run the car to running tempiture and recheck to see how it idles...remember turn the adjusting nuts a tiny bit at a time..then once you think you got it pull the plugs one for the front carb and one for the rear and see how they look ...there should be a chart in your haynes or chiltons that tell you how to read the plugs...otherwise i'd get a colortune or borrow one...i got one and i love it..p.s. becarefull its better to run too rich than too lean and burn a valve up....good luck michele

 

[ian240z]

All you could ever need....

Cut and paste the following links - more info than you can shake a big stick at!!

http://home.istar.ca/~datsun/att06.htm
http://members.home.net/zcarz/projects/tutorials/su-062501.html
http://www.mame.mu.oz.au/salman/S.U.html
http://www.sonic.net/~kyle/su.html
http://www.aptfast.com/APT_Parts/SU_Parts/a_SU_components.htm
http://www.solnet.co.uk/carb-hosp/
http://www.jetlink.net/~okayfine/sutech.html

 

[luggnut73]

Re: All you could ever need....

Son, what was posted before me was right only, If you stick your finger in the throat of one carb , say the rear one and lift the slide about 1 inch with the engine running , this dis ables the carb. and the engine should idle roughly but not quite die , If it dies your too lean, back the adjuster out clockwise about 1/4 turn and check again. when the engine will still run then repete on the front carb and adjust the rear one. Then drive the car for a few miles and check the pluggs for rich or lean. and go from there .The best if you ahve $50. bucks to spend is to get a color tune. Hope this helps , remember disable one carb and adjust the other. . Gary Portland Ore.