I ran 2.3's for a long time and never had a failure with the stock shaft or gear. But that said from day 1 I would remove the fuel pump lobe (electric pump) and turn it down smooth and make sure of the pattern and also the dist. shaft was free. Had a couple rebuilt ones tighten up. I did this for another racer that was breaking them all the time and he tore it up first night out but was a start it up and go on the track guy that did not think you should allow the motor to warm up and the oil either. I would idle my motors to 200 degrees and shut it down and let it soak about 15 minutes before I went out. As for the Melling oil pumps, check them before you put them in. I lost a brand new motor when a yellow o-ring got stuck in the releif system. Never saw a yellow _o-ring in a 2.3 ever.