Mobile 1 Classic oil??

[Woody500]

I tried Mobil One when it first came out. Took the 273 out and wrung it out for about 10 miles. Didn't like the hot oil pressure, drained it out and put Valvoline Racing straight 30 back in and dumped the Mobile One. Never looked back.

If its that thin, you need tighter bearing clearance to keep pressure up. Newer engines have tighter clearances.
So not right oil for build. & pump may not like it, and so on down the line. Someone asked if hone cross hatch still there. Any scuff on pistons?

 

[66fs]

Ran fine with real oil for the next 100,000 miles and never used much oil between changes. I only pulled my favorite 273 when you couldn't buy pump gas good enough to run it. TRW forged 10.5:1 pistons (no scuffing), honed with torque plates with a plateau finish file to fit Speed Pro moly rings. Heads were 64.7cc chambered 1.88 intake valve "J" heads off a "72" 340. I don't care for light oil. I won't even run it in our new Hemis.

 

[Ant]

@johnboy73
Where did you buy the oil from?

Did you remember to take the plastic off the new oil filter?

Did you check your thermostat?

How hot did the engine get and for how long?

Got pictures of the damage?