[greg64]

Dusty, you're talking 400 small block aren't you? Not transmission.

I think engine life comes down to how frequently the oil is changed, and how many short trips (cold engine starts) the engine has to endure. And of course, abusing the engine or overheating it won't help either.

After that, I think the 400 is at a disadvantage compared to a 350. Shorter rods put more piston thrust on the cylinder wall (faster wear). The piston has to travel further for a single stroke (more wear), the piston speed is higher. The cooling isn't as good (siamesed cylinder walls). On the plus side, the main bearing journals are larger in diameter.

But in the end, i suspect how the engine is cared for might count for more than the above design factors.