Race distance engine

[F1Pete]

I am just grasping at straws here, but if I blew an engine during practise or qualifying I would be forced to start at the back of the grid right??? Well, what if the second engine I had for the race was like the previous qualifying engines where they were only designed to last a short time. If an engine was designed to last a race distance only, would it be competitive enough to win from the back of the grid?? I know this is a stupid question...I just hope you guys understand where I am coming from. It just hit me while watching qualifying this morning...when all you hear about is reliability being built into an engine.