Break In

Bob Evans

Grumpy Old Admin
Staff member
Proper break in of your motor is very important to it’s overall power output and how long it maintains this level of performance,. We didn’t go to all of his trouble to rush at this point. There are as many ways to do this as you have builders but the idea is to do it a little bit at a time without just rushing out and running the motor wide open after you get it buttoned up and filled with oil.

Many people will simply fill the motor with 14-16 oz. of any good grade motor oil or the racing oil they will choose to run and run the motor for several cycles at a higher than idle speed for various lengths of times. If you choose to do this try the following.

Run the motor around 2700 for 10 minutes and then shut it down and let it cool off for 15 minutes. Repeat this cycle 3 times and on the third time vary the rpm level up and down a bit after the motor has heated up(200 degrees). Don’t rev the motor wide open on the stand with no load!!!! Great way toss the insides all over the place. After these cycles drain the oil and fill it back up with your racing oil of choice. Then just take the first couple of laps during practice a steady pace. After that.... go for it or as some say “Let that tiller dig@”. If you have access to a dyno you can run the same cycles on the dyno but applying a light load on the motor. During the third cycle run the load up a bit as you vary the RPMs..

One recent trick that many builder are doing these days is to break the motor in on an electric break in stand. I personally do all of my motors this way and it works very very well. All it comprises of is simply an electric motor, such as one off a air compressor, that has enough torque and RPM to turn you motor over at around 1500 to 1700 RPMs. Mine is an old compressor motor than we tied to the motor with pulleys and a V belt. Nothing fancy at all.

When you do this be sure to have you head or torque plate installed to keep the cylinder straight during this process. You will be amazed at all of the small particles from the rings that will come to the surface of the piston. Simply wipe these off as the motor is turned over by the electric motor. For a cool bore we like to leave ours on for around 45 - 60 minutes. I/Cs seem to do best around 60-90 minutes. You will know the rings are seated if no oil is coming up over the rings onto the top of the piston. While some motors will not throw this oil, 90% will and when it stops the rings are pretty well seated. This light break-in method seems to work very well and afford you the opportunity to open the side plate and make sure everything is fine before completing the assembly.

I like to have the valve, springs, and retainers on the motor when running it on the break-in stand. I have a friend who uses an amp meter hooked to the electric motor to let him know when it’s not pulling as hard(motor broken in). This process does not preclude you from breaking the motor in under load. You will still need to break it in either on a dyno with a constant load or by running it at the track under a constant RPM(3500) for a few laps. This will help seal the top ring. I highly recommend that if you breaking in a plate motor do it WITHOUT the plate as this will help build more cylinder pressure and insure that the rings seal!!!