Re: rough running at high engine speeds

Posted by prentice672 On 2017/10/28 10:25:43

Yes, it's the 356. As I mentioned in one of my posts, the "Repair and Tune Up Manual" says the gap should be between .0125 and .0175 (although the tune-up chart just says .017, period). The dwell is listed as 27 deg in the chart and in the Service Manual specs. I always try for .016" and when I had it at that gap the dwell was around 22 deg I think. When I realized the point gap was having such an influence on the high speed roughness I gradually went to .012" point gap which seemed to give normal performance (i.e. no loss of power and/or roughness). At that point gap the dwell is now 30 deg. Now, I'm using an old 12 volt dwell meter I've had since the early '70's but it seems to give a reasonable number on the dwell.
When I replace the points, I leave the distributor in the car, turn the crankshaft by hand with the fan blade and just measure the gap with a feeler gauge when the cam follower is on the tip of the lobe. I suspect that there is some error in doing it that way and that the gap may be actually within the .0125 to .0175 range. Some of the guys on this thread say they set the point gap with the distributor removed which seems like a much more accurate way to do it, although you have to be careful about marking the cam position and the position of the distributor itself. I'll probably do that the next time I do the points.