I Have a 1999 mustang gt with 160k Miles that has a loud knock at high RPM .
Should i just buy a used motor or just rebuild it if rebuild is best what all should i replace? What can i replace to gain more Power?
Define high rpm. When does the knock specifically occur? Off hand, I can't think of any knocks that are only present at high rpms, so it is possible you don't have to replace the entire engine.
Define high rpm. When does the knock specifically occur? Off hand, I can't think of any knocks that are only present at high rpms, so it is possible you don't have to replace the entire engine.
A rod bearing will typically be loudest at light loads and moderate rpms. For example, reving in neutral or in light driving to 2000-2500 should produce about the loudest knock. I think of high rpms as being 4krpm, so if your knock doesn't start until 4000 rpm, then it probably isn't a rod bearing.
Sounds like a stock replacement bottom end would work fine for you.
Not sure what your plans are, but I'd go find a Mark VIII short block from the local junk yard, have valve reliefs cut into the Mark pistons and run some nice high lift cams. High compression cammed 4.6 FTMFW
You already have most of the parts there to do this swap, and you'd benefit from the lighter aluminum engine block.