Re: Break In Period

Posted by Rusty O\'Toole On 2009/12/27 10:47:22

The sleeve valve engine was a very long lived engine, at its best when most engines were worn out, but not at its best when brand new.

In full power tests against a Cadillac V8 in the 1920s, on the dyno test stand, the sleeve valve engine was running perfectly and producing more power after 100 hours at full throttle than at the start of the test.

The Cadillac was a smoking clattering ruin, producing about 70% of its original power.

Sleeve valve engines have a lot of friction. Over time the parts get polished smooth and the friction is reduced, while carbon buildup actually improves the seal.

I would think the long idling breakin would polish the parts and encourage carbon buildup where it was needed. Basically accomplishing overnight, what would take 250 miles of driving at 25 MPH.

Another thing about sleeve valve engines, they are not at their best until completely warmed up and this can take a long time.

An old timer I knew used a Willys Knight as a tour car in the 60s and 70s. He told me that it would burn a quart of oil in the first 60 miles, the rest of the day, nothing. The next day it would burn a quart in the first 60 miles, the rest of the day, nothing, no matter how many miles he drove.

The big advantage of the sleeve valve was not just the silent running, but that it would keep running perfectly far longer than a poppet valve engine.

In addition to the higher mileage between overhauls there was the reliability factor of no burned valves or broken valve springs which were a common breakdown in those days.

For the high mileage driver this was ideal, and worth putting up with the problems of starting, and higher initial cost. But for most owners it was a waste of money.