Hi Ed. After you've checked it a few times, don't worry about it. I haven't checked mine in 3 years plus. No issues! I would be careful about block sealer. My radiator had problems flowing well because of too much sealer before I got the car. Good to see you're still around. Ron W
You said you heard the noise after putting on a muffler. Make sure the muffler isn't loose before rebuilding the engine. If you have the pan off, measure the forward and back movement. If it is excessive, then you can worry. Ron W
As Tom has indicated, you are reading the pressure required to push the oil through the filter. When the filter is plugged it reads high. That's one way to tell. Mine exceeds 20# when revved up cold. It is full flow (no by-pass) and all oil must pass through the filter before flowing up into...
Mine has two 1/8th " holes to allow some circulation while warming up. I've never had a problem. The hot water must be able to reach the thermostat before it boils. Ron W
A 5.2 head would not produce 100 psi unless it has been milled. It sounds like you have a hot spot in the combustion chamber which could be caused by a sharp edge (among other things) from the milling or running too hot a plug causing it to glow. Make sure there are no sharp edges or carbon...
If your engine is pressurized 180 is good. If your engine is not pressurized 180 is only 32 from 212. 160 gives you 52 degrees of safety. I use 160. Ron W
Graphite grease is often used in high pressure applications. It is commonly used in saw mill machines. I think that is what you have. There is no need to replace or condemn parts that are not worn. Ron W