If you are running non-roller lifters I would highly suggest running diesel oil since it has zinc in it unlike most modern gasoline-application oils. You can also buy zinc additives, and expensive "designer" oils with zinc, but diesel oil is cheap and readily available.
This is a very time relevant post. If it were written before 2016, it would be absolutely correct. But since we are past 2016...it is no longer current.
Diesel engine oil was revised in 2016 to the API CK 4 standard. Gasoline engines got the API SN revision. Both limit the the critical additive found in ZDDP. Yes, there are replacements, and yes...Phosphorous is not the only additive, and yes, zinc is part of the package.
Your engine was designed to run API service grades that has an additive package including 1200 PPM of phosphorous. That designation was SH, and there have been 5 "upgrades" since. In 2001, the oil upgraded to SL, and reduced to 1000 ppm. Then in 2004, version SM was invented, and it was further reduced to 800 PPM. The most recent revision was 2016, at SN, and it is still at 800.
I am not here to argue the validity of the need for the proper detergent and additive package for your engine. I am not here to tell you that flat tappet camshafts started having premature wear starting about 2004. I'm also not here to tell you that Comp Cams had a significant rash of defective cams at about the same time. What I will tell you is that if you run any lubricant that is not specifically approved by the OEM for your engine...you run the risk of consuming all of the additional bandwidth and safety factor of the design, and then EVERY design feature suddenly becomes important.
I can also tell you that there is no OEM that will certify any new oil for use in a 50 year old engine. So while the API will tell you that they are backwards compatible...the empirical evidence is overwhelming that the API is not always correct. Ford's recent de-certification of CJ 4 oil is a timely example.
What that means is that if you run oil made to SF or SG...then cam hardness, lifter hardness, spring pressure, viscosity, age, RPM, break in period, etc are less interesting. If you run SL or SM or SN...then suddenly spring pressure, break in, lifter metallurgy, and cam hardness become important. I will guarantee you that NO ONE that rented a Ford passenger car from 1967 to 2021 every bothered to respect the break in rules.
I get paid to replace flat camshafts in vintage cars. And I personally run Lucas racing oil in my flat tappet, low performance, low compression Bronco. I also run it in my Shelby. But for my Tigers, I run a roller cam.
