305 Chev’s are problematic engines. If there is any chance it is not a roller cam, you NEED a thicker, high-ZDDP oil for engine life.
A synthetic 15W-40 HDEO would be just about perfect, as I don’t think it will see cold temps.
BTW, very nice car that is now rare and valuable, hope you enjoy it!
Well, mine wasn’t problematic at all. Ran great. Used Mobil 1 5W30. Sold it when I couldn’t fit a car seat in it.
The issue with the 305 was power. It was a 2 bolt main engine, so, it would not hold up to high horsepower, but that wasn’t usually a problem as the small valves (1.86/1.50 I think) just didn’t flow much, and neither did the “smog” heads.
Like I said, in 1987, the T/A and IROC Z, had roller cams, but it may be that they were only in the TPI engines, and the L69 HO, as well as the LG4, q-jets, still had flat tappet cams.
A guy in my flight school class bought a brand new 1987 T/A with the TPI engine (Pete Wilkins, now a United Captain) We talked about the roller cam. Running the two cars was a joke. My LG4 was so slow by comparison…
Finally, the car I wanted was the 1986 T/A HO with a 5 speed. When I was shopping, in 1986, it was about $17,000.
I just couldn’t afford it. Got through all the RPO paperwork with the dealer, and just couldn’t make the numbers work on Ensign pay.
I got my 1985 LG4 automatic T/A with 20,000 miles on it for $10,800 from the same dealer in Corpus Christi, TX.