PCE in the part number is Pro Comp products right? I built a BB Chevy w/ a set of the Pro Comp 320 cc heads on it. They hadn't been run very long before I went through it, but it had some severe valve guide wear. Soft materials.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax