High RPM miss above 80c

RMartin · 05-31-2005, 05:23 PM

I'm having trouble with an engine miss on my 68S that starts at about 5000 rpm. If I take it out and let it warm up to 60-80c, it runs perfect all the way up to 7000 rpm. If I drive it a while on a warm day the oil temp runs about 100c, the hotter the engine the more it misses.
The plugs, plug wires, cap and rotor are brand new. I just cleaned the carbs and replaced the fuel filter and checked the flow from the fuel pump.
From what I've read on this board it's probably in the ignition, but everything is new. I'm running out of ideas.

RMartin · 06-01-2005, 02:38 AM

bump

ruf-porsche · ruf-porsche's Garage

Everything is brand new but you didn't list point. Check the point on your dizzy. Is the gap correct? when was the last time the point was changed?

You may want to replace the condensor while you are at it.

RMartin · 06-01-2005, 10:03 AM

I forgot to say that the points are new also. The only thing I haven't changed is the condensor on the dizzy.

ruf-porsche · ruf-porsche's Garage

Change the condensor and see if the problem goes away. It appears to be a problem that is heat related and the condensor is a likely culprit.

buster73 · buster73's Garage

Have you checked your ignition timing at elevated temperatures. Could be the advance mechanism sticks once the engine gets hot. I guess you are running a distributor without vacuum advance (if not it could also be a vacuum leak developing at higher temperatures).

RMartin · 06-01-2005, 12:42 PM

I'm going to order a new condensor today. I haven't checked the timing at elevated temps. Sounds like a good idea.

RMartin · 06-01-2005, 02:56 PM

My car has a condenser on the coil and on the dizzy, is this correct?

DByers · 06-01-2005, 03:14 PM

I recently had a problem that I thought was ignition above 5k on my 71. After letting someone else drive her I could tell from the sidelines (track day) that it was a slipping clutch. It was hard to tell from inside the car but clear as day from outside. Not saying that it is a clutch problem, but it may not be the ignition.

RMartin · 06-01-2005, 04:33 PM

If the clutch was slipping wouldn't the engine rev? Mine is definately cutting out.
Anyone else have two condensers- one coil and one dizzy

DByers · 06-01-2005, 06:13 PM

Yes the clutch would slip. For me it went from 5k to 7k quickly. It was the lack of power and "miss feeling" that led me to think ignition. Wasnt till after a few laps that the clutch proved to be the culprit. Just saying maybe its not electrical. Have you checked the fuel system? Seems as if you have eliminated/fixed/replaced the electrical portion of what might cause the miss.
Hopefully someone like John W. or Grady Clay will see this post. If not you should PM them, they could help you for sure.

RMartin · 06-01-2005, 07:08 PM

Once mine starts missing it doesn't want to rev higher, so I don't think it's the clutch. I've been through the fuel system also, since it seems to be heat related I think it's electrical.