Re: [Chrysler300] 300C tune up

[<smopar@xxxxxxxxxxxxxx>]

Most of the time, the instruction to disconnect the vacuum advance when setting basic timing is a precaution.  Sometimes if engine timing is set incorrectly (retarded) to begin with, the carburetor throttle opening at idle when set to the correct idle speed will be too large, exposing the vacuum port used for vacuum advance.  This will provide some vacuum advance at idle, which shouldn't be happening normally.  The normal operation is for there to be no vacuum at idle, and then just off idle vacuum advance will take effect.  So just to be sure the basic timing is set correctly without influence from an improper throttle setting, the service manual instructs you to disconnect the vacuum advance and plug the carb outlet to ensure proper basic timing setting.  So there is probably nothing wrong with your vacuum advance.  Around the later 1970s, manufacturers started using distributor calibrations that actually relied on full vacuum advance at idle to obtain a smoother idle and improved fuel economy, but there were other changes that made that a practical move such as reduced compression ratios and exhaust gas recirculation that minimized pinging just off idle then.
Steve Albu  

---- Mark Schueller <f41324@xxxxxxxxxxxxx> wrote: 
> Hi All:
> 
> I plan to tune up my 300C soon; it's not running good.  I understand that timing is set at 4 degrees BTC with vacuum advance disconnected and vacuum outlet at carb plugged.  What should timing advance to at idle after vacuum advance is then reconnected?  It seems my vacuum advance isn't working.
> 
> Is there an article or book that could guide me through the tune up process on my 300C hemi?
> 
> Thanks you,
> 
> Mark Schueller
> 300C,F     .    
> 
> [Non-text portions of this message have been removed]
> 



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