Breaking In a Rebuilt Engine

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Date: 19 Feb 98 12:34:53 PST
From: Norman.Goetz@directory.reed.edu (Norman Goetz)
Subject: Breaking In a Rebuilt Engine
To: Toy4x4@tlca.org

- --- You wrote:
My question is - what is the proper way to break it in after I get it 
running? I know I should not run it hard for a while, but how long? 
I've also heard different things about how to run it easy. Some people 
have said to let it idle in the yard all day. Others have said to go 
for a nice mellow drive. Some have said to keep the RPMs fairly 
constant, others have said to make sure to vary the RPMs.
- --- end of quote ---

I'm not that sure on the distance, but I'd say 500 miles with the first 100
critical and some care out to 1000.

You should avoid running at constant RPM and keep RPMs on the high side but
truck speed not over 45-50.  Do moderate (~ half throttle) accelerations 
from medium to high RPM over and over.  You want to "work" but not stress 
the engine toward the top of its torque curve.  I had best results by 
driving this way across Kansas for the first 500 miles - no normal driving, 
just repeated acceleration and coasting.

New cars these days come with much of this breakin process already done on 
the bench in the factory, but when you rebuild yourself you must do it all 
yourself on the vehicle or throw away some of the value of the rebuild.  
I figure that decades ago manufacturers found that too many buyers would 
significantly shorten the life of their new engines because they couldn't 
resist the chance to race around right away in their new car instead of 
following the recommended breakin procedure.

Norman

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Date: Thu, 19 Feb 1998 13:19:00 -0800
From: "Smith, Patrick S." 
Subject: Breaking In a Rebuilt Engine
To: "'Toy4x4@tlca.org'" 

Further to Norman's good advice:
1.  The idea of keeping the rev's up is to ensure the engine is always
making a good oil pressure, so avoid extensive idling.
2.  I've also been told to downshift more often and use the engine
compression to slow you down (more shifting, less brakes) in the first 100
miles.  Apparently this helps speed up the break-in and puts the motor under
a variety of load sequences rather than just those experienced during
acceleration.
3.  Change the oil ~3 times, at 100, 500 and 1000 miles.
4.  Patience:  500 miles of patience should be rewarded with 100K of 
partying.

Enjoy,
Patrick
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Date: Tue, 03 Mar 1998 14:50:10 -0800
From: Jerald Josephs 
Subject: Breaking In a Rebuilt Engine
To: Toy4x4@tlca.org

Smith, Patrick S. wrote:

> Further to Norman's good advice:
> 1.  The idea of keeping the rev's up is to ensure the engine is always
>
> making a good oil pressure, so avoid extensive idling.
>

Actually, the reason to keep the RPM's high is to account for
whateverslack may exist between the crankshaft, rods, and pistons.  The
faster
you go, the farther up the cylinder the piston travels.  We are talking
micrometers here, but the idea is for the rings to work the cylinder
for the entire length of the longest possible stroke.



- --
Jerald Josephs   Nokia - IP Routing
jerald.josephs@iprg.nokia.com 232 Java Drive, Sunnyvale, CA 94089
http://www.ipsilon.com  Phone:  (408) 990-2000 ext 2175
Fax:  (408) 743-5679

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Date: 03 Mar 98 15:05:11 PST
From: Norman.Goetz@directory.reed.edu (Norman Goetz)
Subject: Breaking In a Rebuilt Engine
To: Toy4x4@tlca.org

- --- You wrote:
Smith, Patrick S. wrote:
> Further to Norman's good advice:
> 1.  The idea of keeping the rev's up is to ensure the engine is always
> making a good oil pressure, so avoid extensive idling.

Actually, the reason to keep the RPM's high is to account for
whateverslack may exist between the crankshaft, rods, and pistons.  The
faster
you go, the farther up the cylinder the piston travels.  We are talking
micrometers here, but the idea is for the rings to work the cylinder
for the entire length of the longest possible stroke.
- --- end of quote ---

Never heard it explained that way before, but it makes good sense.  Anyone
who has rebuilt an engine knows that the greatest wear to the bore occurs
at the top ring, which produces a vertically rounded depression.  Breaking
in at higher RPM would postpone the formation of that groove which would
eventually start robbing compression from the cylinders.

Norman

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Date: Wed, 04 Mar 1998 19:12:33 -0800
From: Jim Brink 
Subject: Breaking In a Rebuilt Engine
To: Toy4x4@tlca.org

Jerald Josephs wrote:

> >
> 
> Actually, the reason to keep the RPM's high is to account for
> whateverslack may exist between the crankshaft, rods, and pistons.  The
> faster
> you go, the farther up the cylinder the piston travels.  We are talking
> micrometers here, but the idea is for the rings to work the cylinder
> for the entire length of the longest possible stroke.

Actually, high RPM is needed to assure proper camshaft lubrication to
keep the cam lobes and bearings from scoring due to lack of oil once the
cam lube wears off.

- -- 

Jim Brink, Toyota/ASE Certified Technician	1986 Toyota Std. Bed 4WD
Manhattan Beach, CA				32x11.50/15 BFG M/Ts
ToyTech@Off-Road.com
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