In a previous thread, I posted about a P0301 misfire. #1 compression was 125. The rest were 160... So I pulled the head and discovered the exhaust valve was not seating correctly. I sourced another 0331 head and had the machine shop magna flux/shot peen/valve job/deck it. Basically the head looked new when I picked it up. I figured while I was in it this deep I would put new lifters, water pump all hoses etc. This job is a lot of work but fairly straight forward. I installed the intake and exhaust manifolds while the head was on the bench. I felt like I could be more accurate on seating the gasket and meet proper torque specs. Once assembled, I added all fluids and started the motor. WOW it was super quiet and idled flawless. I heat cycled it and continued to add antifreeze. Time for a road test. This is where it went down hill... It has no power. Then misfires everywhere. There is a mechanical sound when the misses occur but it idles perfect. Pulled it back into the shop and checked compression. 150 on all 6. Spark plugs were very clean. This acts just like a time when I had the wrong length push rods in a motor I built years ago. I checked all electrical plugs, cleaned the grounds. I then removed the valve cover and re torqued the rockers. All fine. I think it has something to do with the lifters but would like to know for sure before pulling the head again. I used speed pro lifters from Rock auto... What I didn't do it check the valve lift... I should have. Any words of wisdom??