best friend had same thing happen twice. he bought heads bare, did own assembly with new valves. saved 250.00 dollars. bent some valves and pushrods. do over. happened again. he called the magnum guy he got bare heads from and he told him that the guides needed opened up. he did what he was told and now has 10k on eng. runs like a dream. i think it was guy on west coast that had to quit because of health problems. he spent another 800 to save 250.00. sorry for your loss.
That would be your friend's fault there, both times no less.
You always check clearances when you built something from parts sourced from multiple places. Heck, I check my machine shops work when I build my engines. Yeah I trust them, but I verify.
