does anyone know the part numbers of the canfield heads that had problems cracking. I just got my set back from bennett and one head has really rough guide bores and a small crack around one of the intake valves guide bore. The guy I bought them from had piston valve clearance problems so I'm guessing this caused the damage. I wanted to get another opinion on repairing it but I'm wondering if it will be a waste of money if the head has other problems or tendencies to crack.