The engine has Hydraulic Lifters. I know of the sound of solid lifters, it definitely is not valve train noise. The knock is loud enough for my next door neighbor ( who's and old school hotrod guy ) raise an eyebrow. He thinks the oil pump is not pressurizing the system fast enough. I told him I replaced the oil pump with a new Melling pump, he saw that my oil pressure was great at both higher rpm's and at idle. He just shrugged and had no answer for that.
