2.4 conversation to 2.7

[DaveA]

Buy Bruce Anderson's and Wayne Dempsey's books on performance. Excellent information is detailed there.
R/Dave

[Jay Laifman]

I think your thought of sticking with the 2.4 CIS is smart. I've had my 73.5 for over 30 years. It is a fantastic, wonderful car to drive and own. Smooth as can be. Reliable. Great torque already. My own observation has been that there are more longterm CIS T owners than other 911s. Yes, they are not as flashy as the E and S to folks on the boards. But to live with, they are magnificent. And as Pete Zimmerman wrote in his book, the 73.5 is the first "10" that Porsche built.

I've driven lots of Es and Ss over the years. They are absolutely fantastic. But, mixing and matching CIS and non-CIS is a non-starter. Either make it CIS* or start fresh with your case and build a non-CIS car.

I might add that I've also raced mine at autox's and beaten an S and Es. I'm no great racer. And the courses definitely favored torque. And those other drivers could have just been bad - at least worse than me. But "performance" changes for the use and how you drive it. I'd say a CIS T is still a high performance car for different situations.


*I circled back with another comment. This all started with you asking about 2.7 P&Cs on a 2.4. One of the critiques about the CIS cars is that they are so balanced from the factory, that it is very hard to mix and match pieces - for improvements or to keep running. I think there is some validity to that. On the other hand, I noticed some others looking for 2.4 CIS P&Cs, and suggestions that they can't be found. Perhaps that is what you are battling here. Before you jump to 2.7 P&Cs, I'd definitely have someone who really knows wear, examine the pistons and the rings lands. I would suggest that you lean towards new cylinders (if needed) and new rings, but not going to 2.7 unless absolutely necessary. I'll bet that new rings will largely be what you need - and should last for a very long time under how the car will be driven now (that is, not as a daily driver doing 100s of miles a week).

[66S]

My 73S motor with 2.7 RS pistons and cylinders and 46mm PMO carbs runs very well with a nice idle. I have a front mounted oil cooler and no engine mounted cooler just a 993 filter there. On the road on a hot day the oil doesn’t get hot enough to open the factory thermostat in a Troutman housing, it only got hot enough sitting at idle for a long time. I’m not a big fan of CIS, especially at higher rpms.

[Allen,N]

Thank you for your observations in this.