Q: Engine Breakin

[john smith]

When breaking in a new or rebuilt engine, does it matter if you run high
MP/low RPM or high RPM/low MP at 70-75% power?

[Orval Fairbairn]

In article >,
john smith > wrote:

> When breaking in a new or rebuilt engine, does it matter if you run high
> MP/low RPM or high RPM/low MP at 70-75% power?


Yes -- you want to exert enough pressure on the ring/cylinder interface
to achieve a lapping effect between the two. Actually, you could
maintain >75% power for breakin. Normally, you want to be 25"/2500 for a
normally-aspirated engine.

[SelwayKid]

john smith > wrote in message >...
> When breaking in a new or rebuilt engine, does it matter if you run high
> MP/low RPM or high RPM/low MP at 70-75% power?
***************************
I've broken in several new engines by following the recommendation of
using full power for takeoff and climb. Then varying my RPM's by at
least 100 every :10 minutes or so in cruise. This for the first 10-15
hours of flight. Using break-in oil for the first 25 hours, then
switching to the appropriate weight of oil for your conditions. I've
done that with radial engines, normal aspirated and turbo charged
engines with all of them going to at least TBO without excessive oil
consumption or loss of compression.

[Roger]

On 20 Nov 2004 06:32:24 -0800, (SelwayKid) wrote:

>john smith > wrote in message >...
>> When breaking in a new or rebuilt engine, does it matter if you run high
>> MP/low RPM or high RPM/low MP at 70-75% power?
>***************************
>I've broken in several new engines by following the recommendation of
>using full power for takeoff and climb. Then varying my RPM's by at
>least 100 every :10 minutes or so in cruise. This for the first 10-15
>hours of flight. Using break-in oil for the first 25 hours, then
>switching to the appropriate weight of oil for your conditions. I've
>done that with radial engines, normal aspirated and turbo charged
>engines with all of them going to at least TBO without excessive oil
>consumption or loss of compression.

They told me to run the snot out of it.
The only difference between what I did and above was running about 1"
over square and 80% for the first two hours. Watch the oil and head
temps. The rings seated in less than 10 hours and the engine which is
getting near TBO still uses less than a pint in 25 hours (no oil
filter). As I recall, I changed the mineral oil when it got dirty and
then changed to Aeroshell 100 at 25 hours.

"As I recall" in never had to add oil during the break in. OTOH with
2 oil changes in 25 hours neither change ran many hours

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com