Dreaming of a higher revving 2.7

[sketchers356]

Hi,

I am dreaming of doing an engine rebuild just for fun. I know that some 911s can rev to 7300 rpm if not higher. What parts have to be updated to move past the stock 6500 rpm limiter? Valve springs? Ti retainers? How are the stock rods? I know it would be worthless without a cam, but I love the sound.

[toddu]

Rod bolts.....

Todd

[lvporschepilot]

With any engine it's a matter of making power at higher RPM (creating the need for more revs) combined with lightened valve train components and proper springs for adequate valve control, and natural harmonic balancing of the rotating assembly. With a 2.7, the crank has a natural frequency issue north of 7500ish rpm making frequent trips to 8k (granted one is making power there making it necessary) prohibited. Then there's engine life with the thing revving that high.

Ferrari motors, which is actually my area of expertise more so than Porsche, straight from the factory during that era, which would have been mostly 308s, revved to 7800rpm. Those motors do not last maybe around 60k street-driven miles, and that's probably on the high side. With a Porsche motor of that era and awful lot needs to be done to create a similar power band, least of which is a long duration cam creating the need for higher revs.

[Steve@Rennsport]

Originally Posted by sketchers356

Hi,

I am dreaming of doing an engine rebuild just for fun. I know that some 911s can rev to 7300 rpm if not higher. What parts have to be updated to move past the stock 6500 rpm limiter? Valve springs? Ti retainers? How are the stock rods? I know it would be worthless without a cam, but I love the sound.

Pistons. You need forged pistons to safely run 7300 RPM.

Stock rods and bolts are OK to 7300. Same for GOOD valve springs & retainers. Stock crank is good to 7800 RPM provides its been cross-drilled and the modifications performed to the case and middle main bearing.

Naturally, you need camshafts, induction, heads and exhaust systems all capable of 7300 RPM operation.

Porsche made engines in all kinds of configurations and the high RPM ones, specifically the 2.0-2.4 "S" engines as well as the 2.7 RS engine all had specific pistons, cams, induction (Webers or MFI) and heads designed to operate safely to 7300 RPM.