There’s another “must have” item when rebuilding your flat-tappet style engine. We all know that changes have been happening in the oil industry. Guess what, there’s another that you may not know about. The oil manufacturers have eliminated Zinc and Phosphorus from their motor oils. The reason they done this is because of air quality issues.
Where this affects you as an engine builder, is that the zinc/phosphorus combination is what assisted in cam/lifter break in. Without this material in the oil, old style flat-tappet engines have real issues with lifter break-in. That is why you must use an engine break in oil with additives now to prevent premature cam/lifter failure.
Luckily, some companies in the auto parts industry have come up with a zinc/phosphorus additive that works great. Comp cams part number 159 which they call an Engine Break-in Oil Additive is one of the most popular additives. This additive is typically used only for the break-in period of 100-500 miles. Some people feel even more comfortable using a bottle with each oil change if they have a “special” car or truck.
Lucas Oil has a product [Part Number 10063] that is similar and it seems to work really well.