Re: Missing at Higher RPM

Posted by Tim Cole On 2014/4/25 19:28:28

Hi Steve:

You are doing a lot of work but not getting any data so you can make the right decision.

If the dwell reading changes over 3 degrees when you raise the RPM to 1500 then the distributor is a problem. (that's straight out of the Sun Distributor Manual). If you can't get the Packard dwell angle that means you have a distributor problem.

The vacuum advance should hold vacuum. If you simply suck on the line it should hold a vacuum and tug on the breaker plate. You can buy a hand pump to test it as well. If you raise the RPM without being under load the vacuum advance will be active so disconnecting it is retarding the timing. Thus, driving around with it disconnected won't hurt the motor. It will be sluggish. However, if you have some kind of internal carburetor vacuum leak disconnecting the advance might reduce the symptom.

Go to your friendly NAPA and buy a KD adjustable spark tester. You should have at least 20k on that motor preferable 24k. If the ignition switch is shot you'll need to put a relay into the primary ignition to supply adequate voltage.

Next get the car into the misfire range and run it for a few minutes. Then kill the motor. Pull the plugs and check the condition. Soft black velvet means weak spark. White means lean misfire - less likely when not under load but still possible.

Hope this helps.