I was looking at an 88 Iroc, and the guy says it has knock and claims that a new crankshaft will fix it. or a new engine (well no **** eh?). its a 350tpi. How much damage could I cause if I drive it home? (about 40 miles). How much are the odds that only a new crank will fix it? Or would a new lower end be in order?

 

New crank+bearings for rods and mains is a new bottom end. If you take the time to do that then do the rest as well. Engine with a bottom end knock is probably indicitave of other problems and wear. Negoiate the price based on the need for major engine work....remember it all has to come out to replace a crankshaft. Don't buy it for a penny more than your price...not his or you will need KY along with the shaft.