loud knocking noise from 1997 GMC 5.7L engine
 

I just replaced all lifters and new valve springs. Adjusted all lifters. No oil from push rods while manually turning oil pump to prime motor. I'm not sure what was going on with that. Anyway I finished putting everything back together and started motor. A loud knocking noise started immediately after starting motor. My guess is that the lifters are not getting oil but why that is I don't know. Any help would be appreciated.

Why did you replace the lifters and valve springs? I have a 1998 K-1500 and haven't needed to change any of those. You must have had a reason which might lead to a
diagnosis and solution to your issue. Did you prime the lifters with oil before you installed them I hope? Some brands used to come pre-primed, but I don't think that is the case anymore.

The engine was making a lot of lifter noise and when I removed the intake manifold I found several lifter springs broken, so that's why I replaced them. The machine shop checked the heads and installed new springs. When I installed the new lifters I followed a you tube video saying not to prime them and made the adjustments accordingly. There's so much information out there that you don't know whose right and whose wrong. So today I'm going to try and figure it out.

Another thing that I noticed was that the oil pressure was close to 80. Maybe something is plugged and the lifters are not getting any oil?

watch one of those tv shows when they rebuild an engine they always soak the lifter in purple stuff a day before they install. the noise might be from the push rod/ rocker arms due to not soaking the lifters