I'm having to replace the crank and main bearings in my 2.8, which only has 1200 or so miles on it from a fresh rebuild. Since a new crank/main bearings would have to settle again, and in light of the opposing viewpoints about engine burn-in(push it 100% from the get-go vs. baby it/strict burn-in procedure), would a 400 mile trip through the mountains(and back) be a terribly bad idea? Very hilly area, speeds likely not to exceed 70 at the max.

 

i was always a fan of the method of varying speeds, loads, conditions during break in. never failed me yet. i don't recommend beating the ever living **** out if it but don't run it at idle speeds either. after a few miles you wanna open it up once or twice. if it breaks it'll happen within the first 20 miles. since your just changing bearings you don't have to worry about seating the rings, which is the reason alot of guys say to beat the **** out of it right off the bat to get the rings to seat quickly

 

My main concern is that within a week or so of the engine going back in, it's going to see lots of low-end in the mountains along with extended consistent 70mph on the straights. I'm worried that will be too much on a fresh crank/bearings.

 

i think you'd be fine. just use a good oil for break in. i'm using Brad Penn 10-30 oil in my V-8 S-10. not cheap but it has all the goodies that are nessesary for proper break in.

 

Comp cams recomends for break in (Flat tappet cams) Rotella T motor oil (its for Diesels) Do not use syn oil.

All the engines I have broke in keep it under 2000 also 55 mph first 500 miles.

At first start bring it up to opperating temp at 1000/1500 rpm. then shut it off and let get dead cold. any hot tight places will cool and get bigger and stay cooler.

after 500 miles a quick heavy foot jab to 2500 rpm will help seat things. then ease off and drive like your dad.

Long steady speeds are not as good as up and down, 2 lane vs 4 lane.

change oil and filter at 50 to 100 miles, the first time.
check the oil every time you you drive the first few days.

I keep cars for decades not just years. This has worked for me. Chevies and Harleys. At 900 miles did a hot day wot cost me $900 for two scuffed and slapping pistons. I did pass the other guy though. Now I run 2000 miles before the fun begins.