Old ‘80s GM V8s are a special case, the flat tappet cams had a tendency to eat cam lobes inside of 100K regularly. WITH high ZDDP oil!10w30. You might wanna run Shell Rotella T 15w40 with it's high detergent for awhile.
That's a low compression, small cam engine, so Zinc is not an issue.
HahahaThe only success stories surrounding a 5.0L I'm familiar with is removing it from the chassis and replacing it with anything other than another 5.0L.
However, they do seem to run forever, even when neglected. It's the modern version of the old Slant-Six. Yours even has the same oil bath down the side of the block.
I agree with the others; a 15w-40 HDEO, dino version would be my choice.
Yeah lifter preload, turned until resistance on the pushrod then 1/2 turn moreWhatever xW30 or xW40 is on sale at Tractor Supply, Menards, or Wal-Mart. 15w40 tends to be the cheapest and will work great. I wouldn't worry about detergents too much as that engine looks spic and span inside from your pic.
I assume when you mentioned setting the "valve lash" you meant adjusting the lifter preload? A 305 will have hydraulic lifters and will want a three quarters turn of the nut past zero lash. If you adjusted it like solid lifters, you'll probably hear all kinds of funky noise.
I had one that the cam lobes went flat at 32,000 miles. Oil was changed @ 3,000 miles with pennzoil oil and a Fram filter. 3yrs old and GM would not warranty it.I'm not really sure how many miles this thing ran, looking under the covers i was surprised how clean it was, I'm thinking due to the leak it was always running low, I was thinking the T4 10W30, but yeah maybe 15W40
Soft lobes or lifters that can't rotate. Some blocks were made with not enough clearance for the lifter(s) to spin.The 1981 might have the good harden cam in it yet. Most problems, if I remember right, were 1983-1985 soft lobes. I would run a 15-40 plain oil, no synthetic and be happy.