First track day now I need help with a motor problem!!
 

I was at my first track day with my new 911. What a blast!! It ran great for the first half of the day. Then it started backfiring and idling erratically. Seems to be smoking more than usual (looks rich).

Its a 73' with a 78 SC motor and the stock CIS (no O2 sensor). SSI headers and stock CD ignition.

When I turn the key on I hear the whistle from the CD box. Wires look good I have not been able to pull a plug (need the right socket).

It does not have pressure chain tensioners it does have safeties.

Some times (prior to event) when I started the car, particullarly cold, it would run rough. If I turned it off and restarted, it ran fine. Usually did no have this problem after it was warm.


Here is what I am going to look into, any advice greatly appreciated.

Could the timing have jumper a tooth??

I will check compression and timing

Could a rocker arm have jumped off during an over exuberant run past redline??

I feel like it is a fuel injection problem but what could happen so suddenly like that??

Thanks

"Could a rocker arm have jumped off during an over exuberant run past redline??"

You may want to clarify this.

Did you run your engine PAST redline? Missed shift? If you over rev'd the motor, you may want to start with a leak down test to check for bent valves.