I've got almost 200 miles on my rebuilt 394 and it's running just about as well as I could hope. I'm wondering if there's a break in procedure- or even a "guideline"? I've been babying the motor, and I planned to keep on babying it for at least 500 miles, then doing an oil change before getting into it from a standing start, or pushing high revs and such. So- what say you? Best way to break in a rebuilt engine...

She's pretty, but she did give me some ****!

 

At this point, just change the oil and filter and drive it.

 

Cut the oil filter open. If it’s clean, I’d say your good to go.

 

There are more opinions on break-in than there are on "what's the best oil to use". After the cam is broken in (20 min at 2000-2500 RPM), the first 500 miles are considered break in. I subscribe to the practice of driving the engine the way you plan to use it, with the caveat that you want to load both sides of the rings during that period. That means accelerating and decelerating during driving. Avoid long term constant speed driving like freeway miles. Change the oil and filter at 500 miles and you're good to go.

 

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And I always poured half a container of EOS on the cam lobes, the rest went in the crankcase when rebuilding an engine.

 

On any engine I've re-built once I know it's sorted out to run on the road I go to a straight up mountain road, pretty good pitch and about 3 miles long with no stop signs etc. and run it up varying load and once at the top run it down using the engine for braking, run it like 3-4 times to break in rings. I'm kinda old school but have never had an engine on a Harley or car/truck use oil once I've re-built them. Been using this road in Meriden Connecticut for years, matter of fact the regional OCA meet happens in the next town over about 3 miles from there.

 

Joe's advice is pretty much exactly what I did with my G-block. 15 years and 12,000 miles later, it's still all good.

 

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I’m in the medium to heavy accel and compression decel camp. Low gear, give it the spurs, coast down under engine breaking, repeatedly. Then continue on with varied loading & unloading in further driving. IMO & FWIW, with modern rings, roller cams etc, one has about 20-30 minutes of running time to break in a freshly started engine. If running flat tapped cam, break in cam & get out to the load/decel routine as soon as car is ready to roll.

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I agree, modern engines with thin rings with modern material. Helps to have a seasoned block and deck plate finish hone, all things a older guy like me didn't have 30 years ago, LOL. I still like using my special hill to run even a brand new car on.