Gentlemen,
I am currently planning having an engine built on a 67 alu case. Since the price differential between a 2.3l engine with biral cylinders and a 2.5l engine with Nikasil ones is (almost) negligible I lean towards the additional torque of the 2.5l version.

However, I remember that the 2.5l STs had reliability issues with flywheels working lose etc.

So, what is your recommendation on this? Both engines would use the original and balanced 2.0l crank.

Thank you for your advice!