A buddy bought a Chevy with a rebuilt engine small block from a family the owner has died so we dont know alot about it but i know the guy that did the engine he does good work. L think it was re built then the owner installed it. They checked the oil before driving it home and had to add some they drove it less than 50 miles and it was a quart low. I did a compression test on it and it was good. I didnt know what to think when i spotted something there was a case of oil that came with it. Its synthetic i cant remember the brand its been a while but it was synthetic racing oil. I googled it and they said to never use it in a new or rebuilt engine until its broke in. By the looks of the new exhaust it hasnt been run much. It also has leaked some setting all winter from the drain plug. I am going to change oil to Rotella 10/30 i wonder if the rings will ever seat now?
Needs a good zinc additive for break in, especially if the cam was changed. It’ll take a little run time to seat the rings. 15w40 diesel oil is good for break in. Cut open the filter and see what it looks like. It takes some heat and load to get the rings right. Just running without a load won’t do much for them.
I was thinking about covering the radiator to get it warmed up. It could have a roller cam its a 383 with aluminum heads.
Stroked-short skirt pistons with thin moly rings. Pull a rocker cover and peer through push rod ports. plus see if it has push rod guide plates. But just because it's a 383 doesn't mean roller cam. Like JY said 15x40 or 10x40 with zinc additive. Run it on and off the throttle, don't let it set at cruising rpm.
We used to put in first or second gear and run the throttle up way up and then take your foot off all of a sudden. Would do that for five to ten minutes and then send it out. I don't know about synthetic oils and any possible damage. Lately its all I can get for my pickup and the wife's 4 runner. Doesn't seem to have made any difference at all.
I do remember hearing switching to synth you will develop some oil leaks. In my case I have a 7.3 in a pickup with 150000 and switched to synth and did notice a few new leaks.