Breaking in a new engine Question

[Gary Brockman]

Just finished the installation of a new Universal M25XPB in Squall. The PRM transmission is longer than the Hurth so we needed to install a shorter packing box and trim off part of the shaft to get the engine to fit. In order to get proper alignment, 3/8" pads had to be mounted under the engine mounts. To maintain a safe clearance, part of the top step had to be altered.

The Universal manual calls for a 50 hour initial conditioning period requirement.  It calls for running the engine at varying rpms during the first 25 hours of operation. For the second 25 hours the engine may be run at varying rpms with short runs at full rpm.

My question is what is running at varying rpms actually mean. So far, I have ran the engine for six hour, ranging my rpms from 1200 to 2400 for periods no longer than 10 minutes per setting. Is this the right amount of time for each setting, or is it too long, or can I go longer?

I am trying to get the initial 25 hours in by going out for 2 to 3 hours each day so I can have it completed by June 9th before a weekend of point to point races.

Thanks for any help I can get.

[scgunner]

Gary,

The idea of varying engine RPM during the break in period is so the motor doesn't take a "set" at one particular RPM. The manual is not specific about times at certain RPM because it's not that important. It's only important to make sure you're running through the RPM range during the break in period. Of course you don't want to max it out until you've got that initial 25 hours under your belt. Sounds like what you're doing is fine.

By comparison when breaking in an automobile the only caveat is don't run above a certain RPM during the break in period. Since you're constantly changing the RPM in a car during the normal course of driving it's not necessary to worry about varying RPM. While in a boat you will usually run a set RPM sometimes for hours at a time.

I know cars used to have a break in oil which was changed at the end of the break in period. I don't know if your motor has a break in oil but it's probably a good idea to change oil upon completion of the break in period.

[Ron Hill]

Gary : Sounds like you're doing it correctly on break in. 
i
Kevin mentioned "break in oil".  When I installed my M25XPB I used the regular auto oil for break in and then shifted to Mobile 1 synthetic.

a few thoughts