Bad engines…..

Anyone else having problems with camshafts, lifters, and bearing failures ?
Friend has a 2004 700 carb that he has rebuilt twice. All new parts including oil pump, water pump, all bearings, case where bearings set were perfect dimensions, use high zinc oil for brake-in, cleaned and flushed radiator. Change oil and filter every 400-500 miles. All so installed new crankshaft last time. Does anyone know of a high pressure/volume oil pump for the engines.