Possible blown head gasket?

[Cranky]

My guess is it's the friction modifier that you
used. I use Castrol GTX in 3 different engines
and none have experienced valvetrain failures.
2 of those have 50k and 1 went for 125k
before a valve job was done. There was no
to very little cylinder ridge, and no abnormal
cam or lifter wear.

Same here....3 different engines and 3 different brands. My first look was whenever I changed the oil in my 71 350SL bike which was bought in 73. It had less than 5k miles on it! Always found aluminum sediment in the filter but figured that was the nature of the beast being an all aluminum engine but didn't see any in it on my first oil change. Just figured the guy I bought it from had fresh oil in it when I bought it. 2nd engine was a 289 when pulling the stock intake for a swap and saw aluminum sediment in the lifter valley. Didn't snap to that until I saw the same thing in a 360 some years later when pulling the heads to do some work on them (did an intake swap on that engine right after getting the 360 and didn't notice any sediment at that time either and had used it for about 30k miles before pulling the heads).

At that point I knew a bit more about bearings so pulled the pan and the first bearing to look at showed the copper looking through a now very thin coating of babbitt. Every single bearing looked like that but at least the crankshaft looked good still and did mic out good. I used the rest of the GTX 20-50 that was still on the shelf for other stuff besides engines. That was about 85 and by that time it had been used in my engines for about 10 years and have no idea about what the other cars that I used it in looked like since they got sold earlier....but never saw aluminum looking sediment in any engine since I stopped using the GTX.

 

[Cranky]

By the amount of crud in that 383 it sorta looks like it could be allowed to kill/flatten a Lifter after a gazzillion miles ?

Pulled a lot of engines apart in the 70's and a lot of them were pretty gross on the inside but none of them had flat cams. Imo, many oils of that time period had decent lubricity but not enough detergent....except for GTX? In my 10+ years of using it I feel it had more than plenty of detergent and not enough lubricity.

 

[Fury Man Van]

Wonder a valve was very tight then froze? Was that bent push rod on the worn lifter? Check valve lifter was pushing.

Yes it was

 

[Fury Man Van]

By the amount of crud in that 383 it sorta looks like it could be allowed to kill/flatten a Lifter after a gazzillion miles ?

I agree but surprisingly enough the cylinders had no ridges at all.