Just got my remanufactured ls1 put it. What is a proper break in procedure? And for how many miles? I was driving a rental for a month and getting back in, she's got some power! The old engine had 55k, is it possible to have a more powerful engine now? (possibly better compression because new or something) Yes, I did a search, all i got were threads about things that "break", lol.

 

be gentle for 500 miles and change the oil, then have fun. opinions and procedures will vary depending on if you read the original owners manual compared to what some magazines say.

 

here it comes...lol. there are so many opinions on this, but i will tell you the one i follow: the rings will NOT seat properly without proper combustion pressure, this presses the rings agaisnt the cylinder walls making them conform to the right shape as they should, if you drive easy there wont be enough pressure and the rings will be "along for the ride" wearing in an abnormal way that will produce less compression, and not seat properly....this means you need to vary the rpms and drive it somewhat hard, not like granny on the way to the church house and not slammin down the quarter mile every chance you get, but somewhere in between, more towards the latter. If you notice, many professional engine builders prefer to break-in an engine on a dyno, putting it under full load, they do this for good reason. some say dont run synthetic oil at first either, after a few thousand switch over to your favorite synthetic like Mobil 1. Synthetics are a little better on the friction reduction, so they dont allow the rings to seat as easily, but all in all it doesnt really matter if you use synthetic at first or not, its mainly the seating of the rings and varying the rpms thats does the trick. That is my opinion and by no means am i saying this is the ONLY correct way, this is just what i do and so do many engine builders, and it works very well.

 

I like to cruise around the back roads in 2nd gear. Get on it a little (50% throttle) to put pressure on the rings, then let off the gas in gear so vacuum draws oil up past the rings, then get on it again. Then just cruise for a bit and repeat. Roads with curves are ideal for this.

Then there was the original 350 from my 71. I rebuilt it while home on leave, drove it moderately for a day, changed the oil/filter, then had to get on the road the next day. Drove it ~ 1k miles at steady 70 mph. Engine broke in just fine, so not sure if one way or the other matters.

But I do like to change the oil a day or two after startup to get rid of all the lint/trash/wear material that inevitably ends up in any fresh engine.

 

The Owner's Manual says something to the effect of "do not exceed ~55 mph for the first ~500 miles" ... well, that's just bull. After about ~60 miles on my odometer, I took the car upto ~100 mph under full throttle but gradually applied it instead of stomping it off the line ... did as much speed/RPM varying as I could (with an automatic) and my car now has ~57k miles on it and has never smoked or used excessive amounts of oil, and it's done several passes down the 1/4 mile. A theory I've heard from my Dad and a few other "old timers" is "drive it how you're gonna drive it" whether that be like Grandma or a bat-out-of-hell .

 

When I rebuilt the the LT-1 in my current car, the break-in procedure was as follows. I started it, checked everything for leaks, etc, and let the thermostat open. I let it cool off and took it out on one of the back roads. I put it in second gear and accelerated at about half to three-quarters throttle, and then let it coast back down to 20 MPH or so. I repeated that about ten times to seat the rings. The next day I changed the oil, and took it out and ran the **** out of it. Changed the oil after 500 miles, and switched to synthetic after 10,000 miles or so. It's been perfectly fine for 35,000 miles. I followed the same procedure when I rebuilt the 357 in my 85 Firebird, and it worked like a charm.

In short, seat the rings, drive the **** out of it, and enjoy it!

 

I was always told "Drive it like you want it to be" I know that dont sound right. When i blew up my LT1 i ordered a brand new long block. When we finally got it running my buddy MR. Goodwrench hopes in the passenger seat and says lets go, ok so i figured we were going for a stroll. Once we pulled out he looks over and says "Don't kill it but u gotta break it in" first straight away we came to he's like lets see it. After that for the first five hundred miles any chance i got, i was gettin into it. Same thing with my new LS1 every chance i got right to the floor. I think it's actually written down in a manual some where. That these things need wide open throttle to run right. Mine has 9332k on it now and i think part of the reason it runs so strong (LS1's do anyway) is because of proper break in. Drive it how you want it to be driven. Good luck man enjoy it, they grow up fast lol.

 

http://www.mototuneusa.com/break_in_secrets.htm

 

what he said