[ischmitz]

I think the 964 share the comon issue of valve guide wear with the older engines. Other than that you are right about a small percentage of the 89 - 91 engines having head to cylinder leaks (mine included) that had to be addressed. And there was the issue with the belts failing before the vent kits became popular.

Another concern on the 964 is the rod bolt diameter. It's 9mm and some say it is a weak link for high-RPM applications. Damage is accumulative and frequently hitting redline can cause the bolts to fail. However, I have not heard about motors here that catastrophically failed.

In general the 964 seems to be a very reliable platform especially after being rebuilt properly with better valve guides and ARP rod bolts. I don't think there are any differences between it and the 3.2. You just have a statistical advantage that produced more high-mileage 3.2 engines by now whereas the 964 engines are younger in comparison. The reason I say that is that you also read a lot more about 3.2 engines being worked on here.

I message board like this will always produce a skewed image of engine reliability. You might want to talk to some of the experienced engine rebuilders to get more objective point of view.

If it was me I would go again for the 964 engine for my early car. I like it for its performance, price point and the fact that is still is a traditional air-cooled engine. With the 993 you get hydraulic lifters and the later 993 have the better intake system. However, from a power point of view I can make almost the same power as the early 993 engines by updating the exhaust.

If your decision is between the 911 Carrera and the 964 Carrera for a complete car there are many more factors that come to mind for the decision. Very different suspension setups, transmission was 915 and changed to G50 later on. More electronics on the 964 that can fail. ABS, airbags, power steering, weight, etc.. I would not make the decision based on the engine alone. Best, test-drive both to "feel" the difference. They are very different cars.

Ingo