Date: Wed, 21 Aug 2002 20:25:33 -0700
Reply-To: Stuart MacMillan <macmillan@ATTBI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <macmillan@ATTBI.COM>
Subject: Engine break in: a synopsis
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Well, due to popular demand, here goes.
Much of this is from my reading over the past 30 years, as well as
conversations with other enthusiasts. All of this is published somewhere,
so I'm not taking any credit for original thought.
Probably the best book on the subject out there is "Drive it Forever" by
Robert Sikorsky. Available used from Amazon.com and others.
What is it you are doing when breaking in an engine?
Seating the rings and "bedding in" the cam and lifters.
That's about it. Modern cars have engines that are designed to do these two
things quickly in the first few miles of driving, and some high performance
engines are run in at the factory before they are installed. Hence,
Corvettes and others come with synthetic oil.
With a rebuilt engine, the cam and lifters are Parkerized, which is a
slightly rough surface hardening on the contact surfaces that is designed to
polish into a smooth surface with proper break in.
Rings and cylinders need to hone together to a perfect mating surface, and
this requires proper metallurgy as well as lubrication. Synthetic oils are
too slippery, so always use a mineral based oil for break in.
The first 100 miles are critical. It all happens here. Good or bad. So,
here is the summary of what I have read and done over the years:
1. Use straight 30w oil, non detergent (just like a cutting oil) if you can
find it, for the first 500 miles. Drain and replace with 20w/50 mineral
based oil for the first 3000 miles. After that, the engine is fully broken
in and you can use synthetic oil.
2. Try to break in your engine in summer, the warm temps will help the
process.
3. Long trips with varying speed are best, avoid lots of cold starts and
short trips, as well as long periods of idling (heavy traffic). Also avoid
high speed driving for the first 500 miles.
4. For the first trip after you install the engine, find a steep hill about
1/4 mile long, drive up with full acceleration, then turn around at the top
and coast down. Repeat 10 times.
The theory behind all this:
Rings need to wear in, and by accelerating up a hill they are forced by
compression into the cylinder walls and "hone in." Coasting down causes
high vacuum which sucks oil up into the cylinders to lubricate for the next
trip up. The same principle applies to varying speed on a freeway trip for
the first 500 miles.
The cam and lifters also need to wear in, and the killer for them is low
speed idle until this happens. The force on the cam lobe is highest at low
speed as it "throws up" the lifter on its shoulder, and as rpm increases,
the lifter stays suspended a bit so the load on the lobe is lessened.
So, the driving most of us do on a daily commute in normal traffic is
perfect for engine break in--varying speeds over a trip long enough to get
everything up to temp. If your commute is not like this, take a 100 mile
trip for your first drive with your new engine.
P.S.: I've used this procedure on six rebuilds so far. I did all this with
my new WBX rebuild and after the re-ring. The second time all worked well,
I now use about 1/2 quart between my 5000 mile changes.
If the rings are junk they will never seat.
Stuart MacMillan
'84 Westy w/2.1 (now with good rings)
