Sacto Mitch posted:
I think if it were me, I'd at least try a simple test to help confirm it's the carbs.
Try advancing the timing about five degrees from where it is now and go for a short, gentle drive (don't rev it very high). Is there any change at all in the flat spot?
If not, the carbs are probably the guilty parties. But if the flat spot does change at all, for better or worse, maybe look into tweaking or replacing the dizzy before messing with the carbs.
After the test, you'll need to set the timing back to where it was (assuming it was right to begin with).
This is not a definitive test, but it may give you another data point, and before investing that kind of coin, I'd want all the data I could get.
I have a master mechanic, who races, and, has been an elite Porsche Doc for 32 years. He has done all of the above AND within 3 minutes of introducing the car to him, told me what I now know: he warned me
that the carbs and the dizzy were a potential issue after a 5 minute drive. He tuned the car, advanced the timing and warned me that it will hold the tune for 4 weeks
if I'm lucky....he could tell that there were air leaks, bushing issues, AND after 30 plus years of fiddling with Webers, knew what ultimately would need to be done......at the same time explaining the Weber purist mindset and the absolute engineering remedy of PMO. There is a reason why Weber stopped making 3 barrel carbs AND moved to Spain.....the Porscheophiles turned on them and the PMO product blew them away.....it was PMOs for brute HP/torque or EFI for full electronic management and scientific efficiency.....or live with the Weber doodles.
By the way, there was no more advance left on my dizzy after the tune.....the carbs were the wrong ones or should I say inadequate for the 2.7RS profile/cam/port size/etc. to begin with and the dizzy could not remedy the issue in any reasonable manner. It was what was readily available ay the time of build and as my mechanic suggested, got a grade of 89 to 91 but would never be 97 to 99% without the PMO upgrade. If I wanted perfection, it would cost $5000 plus for a 97/99 or triple that for PMO/crank fire/ twin plug/12 coils!
I'll take the 97/99 with new PMOs and a remanu/recurved dizzy to fit the build and eliminate all of the Weber doodles. Appreciate the suggestion, indeed, but have already been thru the process with thorough explanations at each stage of failure. I must say, in all honesty, this machine kicks big ass the way it is.....I would just like to get rid of that last bit that represents the cherry on top of the whipped cream. It just isn't a perfect ice cream Sundae without the cherry on top and both Webers and PMOs cost big coin.......gotta do the time when you do the crime