[HO455]

Originally Posted by schovil69

Thank you, everyone, for chiming in here to offer potential causes for this noise. I will respond to all here but let me know if I miss something.

The rocker arm adjustment, or valve lash, has been gone through three times. There was the initial setup on the engine stand where I tightened a rocker arm nut until I could not raise and lower the pushrod anymore then turned another half turn. Second round through the process was after install and initial startup where the engine was bumped over until one valve of a cylinder was fully depressed at which time the other valve's rocker arm nut was tightened until the rocker arm could not be moved up and down. Not all but there were some that required adjusting at this time. The third round through the rocker arm adjustment all rocker arm nuts were tightened between 1/4 to 1/2 turn merely to positively eliminate the potential for them to be loose at all. At no time during any of this adjusting was there any notable resistance.

These Comp Cams lifters sat in fresh oil for a couple weeks before I got around to installing them. Not that the excess soak time makes a difference. I'm hopeful it's not the lifters because those babies aren't cheap. I expect Comp Cams will replace one that is not working properly.

The mechanical fuel pump is not a new unit, however, it was new about two months prior to pulling this engine for the rebuild.

The alternator is a new unit and spun freely prior to install. The power steering is all that's left for accessories. I'm going to skip running without belts, though, as these parts are not the likely culprit given the apparent location of the noise.

The flex plate is a new TCI 399604, https://www.summitracing.com/search/...keyword=399604.

I have about an hour to run over there tonight. The plan for tonight is to pull the distributor and run the oil pump with a priming tool/drill to ensure oil is pumping to the top and that it's not the source of this sound.

Beyond that, the intake will be next. What do I look for to see if a hydraulic lifter is not pumping up or operating properly?

Doing the "run without belts" test will ease or confirm your concerns about the water pump. Without belts the water pump won't be pumping.

Run the engine with the valve covers removed. (Messy! Don't Rev the engine! Google how to use a junk valve cover to cut down on the mess.) Use your listening tool and put it on each rocker stud. You maybe able to locate a specific valve problem or at least which bank. You also will get a good visual on the oil flow to the rockers.

Ten years ago my brand new SFI flexplate failed within 300 miles on my 401. It was cracking around the outside just inside the gear ring. It made me think I had lost a lifter.

Not trying to be too gloomy but, a cracked piston can also make a similar noise. Let's not go into how I know this.

These days I don’t trust new parts to be good parts. Unfortunately it's a sad fact we have to live with.