Re: Miss at Idle

Posted by Tim Cole On 2013/3/13 20:19:05

If the miss is steady then it can be sounded out with a tachomter and a screw driver. Ground out each plug until you find the one with the low rpm drop. That is the cylinder causing the problem. If you can't isolate a cylinder then the problem is in the intake or the ignition.

If you really want to see the problem in action find a place that still has an oscilliscope (rots o ruck). The scope will tell you if it is a plug, a lean problem, a running compression problem, or whatever. If the firing line falls off then that is a mechanical problem like a broken or stuck ring.

One other note on timing, changing the timing on a short stroke V-8 motor is a lot different that on a long stroke motor like the Super 8 which is more suseptible to piston damage from advanced timing. Packard had the proving grounds and those motors were pretty well set up given what they were. The problem these days is the lack of NOS parts that depresses performance.