The torque peak on a 216 is at about 2200 rpm. The torque peak on the bigger sixes is at lower rpm, the 261 peaks at about 1500 and the GMC 302 at about 1300.
The 7 main bearing engines really can stand much higher RPM's, but you have to be careful with that, because the harmonic balancers separate after a while and slip, then become ineffective. Bad harmonics make the bearings wear funny.
The redline on my BMW six is at 7000, they have the harmonics pretty well controlled and the pistons and rods are really light.
Of course, none of it even comes close to my rotary- that thing's power peak is at 9000 rpm. Mazda put a rev limiter on it because the clutch and alternator blow up when you go above that. It's as smooth as a turbine.
Lugging an engine is also bad for the bearings- the low rpm knocking makes the rod bearings slap metal against the crank.
