rough running at high rpms

jim72911t · 08-23-2002, 10:24 AM

Hi all. I have a 1972 911T MFI with 130,000 miles. I did a top end rebuild to stock specs last winter and have been playing with the car all summer trying to get it to run right. The car seems to run well up until about 4000RPM. There is some smoking at higher RPMs and a plug read tells me I'm running rich. I have adjusted the valves, and installed new points, disributor cap and rotor. The timing is correct.
Any thoughts? My fear is that the MFI is comepletely shot. Or, could the fault lie elsewhere, like the CDI box or ignition wires? I have too much time and tears invested in this car to give up on it, but I'm getting frustrated.

TIA
Jim

jim72911t · 08-23-2002, 06:53 PM

Hi again.
I just played with the car a bit more tonight. I forgot to mention that I'm getting some slight backfiring through the exhaust when the throttle is lifted. I haven't purchased an exhaust gas analyzer yet, but maybe that should be my next step so I can check CO levels and properly tune the MFI. I have gone through "Check, Measure, Adjust," and have a pretty good understanding of how the system works. If it turns out I cannot get the MFI to perform within spec, is it worth the $1500-$2000 it would take to properly rebuild the system (remember, this is a lowly "T") or is the money better spent on a set of Webers, or perhaps, a 3.0 or 3.2 conversion? Any thoughts are much appreciated.

Thanks,
Jim