Who is building the engines ? Are they going to warranty them ? If so I would ask them what you should use :)

Personally I have been using the Driven 10W40 Break In oil. I would leave it in for an hour or so of easy running.

Just a local machine shop. They have done some other engines for me in the past.. I got friendly with the owner. I did some HVAC work for them so I am pretty loyal back to them. I never new you can get a warranty unless they are bone stock! and even then try and collect !!! . Its just a refresh with a new cam.. Check out 2nd time here we go again clanking ticking noise after engine shut down

Since we are on this topic, ie: flat tappet oil, this available recently , and also at Walmart. $20 for 5 quarts conventional
. More info:
https://www.castrol.com/en_us/united...x-classic.html
and
https://msdspds.castrol.com/bpglis/F...EPP-BYBE6A.pdf

https://cimg2.ibsrv.net/gimg/www.off...79d6aef37.jpeg

I've built and dynoed a lot of engines. I've used VR1, Amsoil Racing, Joe Gibbs, etc. right down to off the shelf Pennzoil and Valvoline and have never had a cam failure. If you gonna go with a hi-zinc break in oil do it with one engineered that way. The off the shelf additives can do just as much harm as they can good. (Deals with foreign material attaching to the detergents.) Oils are engineered. They spend millions of dollars on the design and testing. Your not going to out do the engineering department by adding anything to the oil.
Also in my opinion, most cams are lost from not using a good moly coat on lobes and lifters along with priming the system. The moly that ARP supplies with their fasteners has worked great for us the last 25 yrs on lobes and lifters.

I just had my 540 Merlins rebuilt,,my engine builder strongly recommends,, Driven ,,break in oil,,straight 30 wt.,,so thats what we used,,

I had an old GM guy (friend) who did a lot of hi-perf builds when I was young poking around on my bicycle and he was the most meticulous guy I’ve ever met when it came to the cleanliness, tolerances etc I’ve ever met. He would also coat all the bearings with moly.

He helped me build my first 383 engine when I was 16 and I’ll never forget when he came to my place and we fired up the engine for the first time and broke in the camshaft by the book. When we shut it down and he went to leave he said what ever you do don’t fire it back up. OK - I was 16 had a Camaro with a 383 double hump camel back heads with the 292 comp magnum cam (was called king of the drive in cam) and just open headers. You think I didn’t fire it back up the minute he drove off. He heard it and never let me forget about that. Lol….

Never had an issue but also never forgot what he said as he had such a great record with long lasting engines.

He recently passed away but I’ll never forget all the little things that are so important that he taught me. Clean clean clean and reclean!!!

ZR -1 and can order from Amazon by the 5 quart case , reasonable and next day delivery .just ordered 12 cases on a Saturday and they delivered Sunday morn by 10.00 a.m.