Trying to set timing

[Stunt]

71 240z

Specs

L28 N42 block/ N42 head

Dual SUs

MSA 6-1 header

Electronic dizzy 78 280z

280zx 5 speed

 

 

Lowest timing I can get is around 900 rpms. The manual says 600 rpms. I need to do this in order to fully tune my dual SUs. Do I need to set mechanical advance and vacuum advance before I can do anything else? Any help is appreciated.

[Six_Shooter]

Are you trying to get the engine to idle lower?

If so, that is not done (entire) through setting timing. Timing is a relation of when spark occurs in relation to the position of the crank, or more correctly the position of the #1 piston (in most engines), to TDC, when the crank is at a specific position.

 

Ignition timing will have an effect on idle speed, but the greater contributor to idle speed is carb set-up, specifically the position of the throttle plates at idle. To get to minimum idle speed you may have to go back and forth between throttle plate position and base timing, if the carbs are far from proper set-up, other wise you should be able to get the idle speed as low as you can, set the base timing to spec and then set idle speed. 

[NewZed]

Indeed, it looks like someone is getting their words and procedures mixed up.

[Stunt]

I found out why my idle was high. I had a vacuum leak on both my dual SUs. Apparently the guy I bought the carbs from didn't put the gaskets between the carbs and the intake manifold. Thanks for replying. Now onto tackling turn signal and combo switch problem. Lol

Edited June 14, 2015 by Stunt