Rough Idle after advancing timing...?

junkcarfann
junkcarfann Expert Adviser
edited November -1 in HUDSON
Well, I advanced the timing on this 1936 T 212 until it just wants to ping when pulling in 3rd gear at about 15-20 mph.



Now it idles like its got a racing cam...lumpy, and carb adjustments do settle it down a bit, but not much.



The car runs teriffic with lots of power, does not ever get hot, starts easily and quickly, and runs smoothly except now at idle it is lumpy, and going up to a stop sign with no throttle the lumpiness makes the car jerk like you switch on and off the ignition.



I never had such a response with any engine before by advancing the timing to where it should be...any suggestions as to what is causing it?

Comments

  • terraplane8
    terraplane8 Senior Contributor
    I'm surprised you can get the engine to ping as my '36T even with 7.3:1 compression won't ping at all no matter what the timing. This is probably due to the high quality of today's fuels plus the still relatively low compression.



    To avoid over-advancing the timing it would be worth working out just how many degrees of advance you have set it to, ie points opening how far before the TDC timing mark on the flywheel.



    Have you put a vacuum gauge on? I found it useful to advance the timing to get the maximum vacuum at idle then back the timing off a little from there.



    There's two threads on this forum I started within the last year about raising the compression on my car and reporting on improved performance in the top gear increments, eg 30-50mph. You could see how yours compares? http://classiccar.com/index.php?option=com_jfusion&Itemid=62&jfile=showthread.php&t=19951&highlight=terraplane
  • junkcarfann
    junkcarfann Expert Adviser
    So you think perhaps I over-advanced it? The ping is very faint, but is there for just a moment.



    I will put a vacuum gauge on it tomorrow.



    Thanks for the reply.
  • Geoff
    Geoff Senior Contributor
    Use a timing light. If you don't have one, use common sense and the "ear-o-meter". Advance the timing until the motor starts to fluff and misfire, then retard until it runs nice and smooth with no popping or fluffing. If using a timing light set it on the first line showing on the flywheel, no further. If it is still running rough, retard one mark at a time. Of course before doing any of this you will check the points for clean condition and the proper gap of .020, and that the automatic advance is working.
  • junkcarfann
    junkcarfann Expert Adviser
    Well, I am an idiot...I found the problem.



    I accidentally rubbed against the choke linkage (manual choke) as I adjusted the timing, thus richening it. Car runs fine now.



    Thanks for all your responses.



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