Subject: Tuning SU Carbs
Date: Tue, 09 Feb 1999
From: zdoc <zdoc@yosemite.net>

Hi Duane, Doc here... I'm glad to hear that you have changed the ignition parts. The dwell should be 36 degrees on the 6 cylinder scale. I suspect that you have the mixture too lean if the timing is OK. You must reach the knob at the bottom of the carbs and turn them equally the same amount CCW facing the carbs from the bottom view. In other words the knobs must go downward to richen the mixtures, so go 1/4 turn at a time. The real indicator is that the engine sped should increase if it is too lean, and start to slow and blubber when going too rich.

Probably the combination of a little too lean and the MTBE Winterized fuel have too much alcohol in the fuel so there is not the potential energy there. I hope that this sheds some light on the subject..........
ZDOC OUT

DRTAIA@aol.com wrote:

Dear Zdoc,

Thank you for your advice the other day about my 1972 240Z (automatic). The points appeared pitted and I changed them with new. I also changed out the rotor, condensers, checked the spark plugs, adjusted the timing and the valves and adjusted the carbs. It is better than it was but it still has a bit of lag when I begin from a dead stop - occaisonally I also get a backfire during this acceleration. Could the float level be a culprit here? It was the only thing we didn't check out when I was down to see you last year.

It looks like it would be a real challenge to get off - you did point out the long screw and nut that attaches to it, but I assume that I would need to take off the carburator to access that.

Any suggestions would be greatly appreciated.

Duane R. Thomson

DRTAIA@AOL.com