'75 S series 2.7L high-speed miss

[snielsen]

I have a '75 911S on which I have recently (3000 mi ago) redone the top end. The 2.7 starts on the first bump of the key, and runs beautifully, pulling strong until it gets to about 5,500 rpm, then it loses power and feels flat. It will still pull to redline, but weakly. It does not seem like a miss, running roughly, but feels more like I have backed out of the throttle; that is, fairly smooth but weak. This is my first Porsche engine rebuild, and I may have missed something, but before I start tearing things apart, has anyone got any similar experience? Point me in a particular direction?

[1974carrera]

There could be a lot of things that might cause a loss of power at higher revs, but if there is nothing obvious you might try eliminating some of the basic, easy-to-check things. Have you checked the timing? You need to set it with a timing light and confirm that the distributor is providing full advance.

[Jim Sims]

Also check the CIS fuel injection system especially the system pressures and the fuel pump pressure and fuel delivery rate (and fuel filter). The system must have adequate peformance from the fuel pump to keep the fuel supplied at higher RPM's (and higher fuel consumption rates) and if your pump is original it may be worn out. Jim