Rebuilt Engine Break-In Period--How Long?

[Steven B.]

No engine oil or additive thread here, but a question. Everyone talks about the break-in period for a rebuilt engine, but what how long is the break-in, 500 miles, 1,000? I have 350 miles on a rebuilt, but don't know when the break-in period ends or how long it should last? And any precautions about running the engine during this phase?

thanks,
Steve

[Clem Z.]

Re: Rebuilt Engine Break-In Period--How Long?

make sure you do some full throttle runs thu the gears to get the pressure behind the rings so they seat.

[Jamie F.]

Re: Rebuilt Engine Break-In Period--How Long?

Here is a topic with as many opinions as well,,, Anyway, accelerating and decelerating is important to seal the rings. Otherwise drive it like you will normally, don't baby it. Some believe to drive it like you stole it, if it's built right it will wear in as it's suppose to.
If you Google break in procedures you will see a whole host of methods. The easy break-in has definitely lost favor over the years. Some rebuilders don't even believe any type of break-in is necessary.
The most important thing is to change the oil after few hundred miles as there will be a lot of metal particles and such in the oil after initial operation.

[Mark F.]

Re: Rebuilt Engine Break-In Period--How Long?

Here is a topic with as many opinions as well,,, Anyway, accelerating and decelerating is important to seal the rings. Otherwise drive it like you will normally, don't baby it. Some believe to drive it like you stole it, if it's built right it will wear in as it's suppose to.
If you Google break in procedures you will see a whole host of methods. The easy break-in has definitely lost favor over the years. Some rebuilders don't even believe any type of break-in is necessary.
The most important thing is to change the oil after few hundred miles as there will be a lot of metal particles and such in the oil after initial operation.

I had my motor built by a master engine builder here in SD that goes by the name of "Driver". He has a very good reputation and builds a lot of race motors. His recommended break-in procedure: Start with a pre-presure lubed motor. In the garage, start motor and immediately take throttle up to 2500 rpm for was 20 minutes to break in the cam lobes and lifter surfaces. Don't let the motor idle as the cam is lubricated by splash. That's it.

As far as metal particles are concerned, if you have "a lot of metal particles and such" in your motor, your builder did not do a good job cleaning.

[Jamie F.]

Re: Rebuilt Engine Break-In Period--How Long?

And if you have a roller cam you don't even need to do that.
All motors no matter how well built are going to have some type of "debris" in the oil. Cam assembly lube, and metal particles from all over the engine. I'm not talking about shaving and chips, but very fine wear in particles. It is good to get that stuff out. Most performance builders will recommend changing the oil and filter after 50 miles or an hour of operation. You don't have to, and your motor will be probably be fine, but after what you've just spent on it was another $40?

[Paul J.]

Re: Rebuilt Engine Break-In Period--How Long?

[quote=Mark Francois (26312);397249]I had my motor built by a master engine builder here in SD that goes by the name of "Driver". He has a very good reputation and builds a lot of race motors. His recommended break-in procedure: Start with a pre-presure lubed motor. In the garage, start motor and immediately take throttle up to 2500 rpm for was 20 minutes to break in the cam lobes and lifter surfaces. Don't let the motor idle as the cam is lubricated by splash. That's it.

This is the old time standard that we've always used, which was recommended to us by more than one good mechanic. We also change the oil and filter after 500 miles. It's cheap insurance.

[Duke W.]

Re: Rebuilt Engine Break-In Period--How Long?

The biggest issue in "breakin" beyond "cam breakin", which is 20 minutes
of running at 2000-2500 upon initial startup, is ring seating.

Up to about the early seventies chromium faced OE top rings took a long time to "seat", but molybdenum faced rings used today require very little time to seat.

With either ring type you want to vary speed and load - brief periods of light to moderate load to force the rings against the wall followed by periods of light load where cylinder vacuum on the inlet stroke pulls oil across the top ring.

This is usually expressed as "vary speed and load", which can be done on a dyno or in normal road driving.

A cam breaking is a good idea. It's not absolutely necessary with OE cam/valvetrain components - GM certainly did no such thing, but it's easy to do and good insurance.

You can effectively vary speed and load by scheduling a road trip of about 200 miles. Starting from about 50-55 MPH accelerate lightly to 65-75, then lift off until the car decelerates to 50-55 again and repeat the process. During this period avoid high load at low revs. Run a gear lower in the city than you would otherwise. After this initial 200 miles start a schedule of brief WOT acceleration runs beginning at 2000-3000 to higher revs with an initial limit of 4000-4500 and increase to the rev limit over the next 100-200 miles to your redline. By about 400-500 miles the engine should be ready to handle any demand - from WOT off-idle to WOT to the redline

The above applies to moly rings. Chrome rings are still available, but should not be used as long as you have a good cellulose air filter. Chrome rings are more abrasion resistant and are often used by sprint car racers, but moly is best for road engines with modern cellulose air filters.

According to research I've read, new engines develop a lot of particles during breakin, then the rate of particle generation falls off until end of life when it rises again. For this reason I recommend changing the filter only after cam breakin. (The solids in cam breaking lubes applied to lobes and lifters can also clog the filter.) Change the filter again at about 400-500 miles, then do a complete oil/filter change at 1000-1500 or one year.

The above assumes you use a C-category oil with a breakin supplement like GM EOS. Beyond this initial oil change a schedule of 5000 miles or one year, whichever occurs first, is perfectly acceptable.

You don't want to drive a new engine "like you stole it", nor do you want to baby it excessively. Follow the above schedule, and if the engine was machined and assembled properly with high quality, compatible parts it should have a long and happy life.

My '63 340 HP engine took a long time to seat the (chrome) rings when new, and full seating did not occur until about 10K when I noticed oil consumption was down and the the blue smoke went away. I was probably too easy on it for the first 1000-2000 miles, which caused the rings to seat slowly.

Duke

[Steven B.]

Re: Rebuilt Engine Break-In Period--How Long?

Duke:

Once again, your knowledge gives me the information I needed. Also, thanks to everyone else for chiming in-my engine and I appreciate it.

steve