Hey :)bestgen4runner,

Well… I’m not sure that will put it to bed. 

Over the years I’ve read hundreds of threads on engine rebuilds and break-ins. 

Comparing a Toyota factory assembly line with millions of dollars of the best equipment money can buy and a DIYer rebuilding an engine in his garage are two different engines. 

Here's my thinking.... 

There can be an issue with China-imports and cheap parts. But, more importantly, the machining of the block, boring, honing, Ra, and cross-hatching of cylinder walls is critical.  Accuracy with tolerances and proper pre-lube during assembly is very important. 

The first 20 or 30 minutes after initial firing of the engine is critical to maintain RPM to keep the oil pressure up to lubricate the camshaft and rockers.  After 20 or 30 minutes after initial firing, the plateau surface in the cylinder walls is mostly likely created. After checking everything over, fine tuning ignition timing, valve lash adjust, etc, etc, driving the truck for another 30 minutes or so, varying the RPMs, with quick bursts of acceleration and decelerating, keeping the RPMs below 4K RPMs while watching the engine temp gauge should get it 90%. I will check the head bolts.......then I’m going to see what WOT feels like to 5,500 in 1st and 2nd gears.    I don’t think that I want to change my $50 worth of break-in oil until it’s got a few hundred miles on it? 

But... I am not an engine builder. 

Gnarls