I just came from the machine shop that's gonna re-build a 6.5 for my '87 'Burb. He had a John Deere industrial engine. The cylinder liners were pitted right thru! The high compression causes a chemical reaction that eats right thru the heavy, good quality steel. Pix to follow. Truckers check the PH level of the coolant to minimize this effect. What should I look for on the 6.2-6.5? Anybody ever see this phoenomina on a "fixed sleeve" block?