Hi,

I have a recently purchased 260z.

The motor has 72 degree cam, 6-2-1 extractors and 240z carbs. [edit] forgot - the guy who built the engine also put in a recurved 280zx distributor.

I have noticed that if I put the headlights on, I lose about 200-300 rpm from the idle speed, needless to say it starts running pretty rough but doesn't stall. A bit of choke brings it back. My question is -

Q. is there a solenoid which adjusts the vacuum when the lights come on? where do I find it? (can't find reference in haynes repair manual). Could this be a simple vacuum leak?

In the past week, I have changed oil, plugs, leads, cap etc and removed a high speed misfire in the process (#3 plug was dead).
I noticed that these changes required a slight increase in the idle setting but produce far better power and smoother delivery overall. I have the gaps at factory settings. So another question :

Q. is it normal if the car gets new oil and plugs after an extended period that the mixture/idle will need adjusting?

Q. is the 25W/50 (penzoil street machine) too heavy for this motor?

Any thoughts appreciated. [edit] - I found a few su tuning guides around and made myself an AFM, so i'll tune the carbs tomorrow and recheck for vacuum leaks - been spoiled by efi for too long...