Break-In Procedures for Remanufactured Engines

This engine has been remanufactured to provide continuous, satisfactory service. Protect your recent investment by following these instructions before installing or starting the engine.
Baril Engine has been a member of AERA since 1986.
This guide is a combination of AERA and Baril’s recommendations.


This engine has been carefully assembled to precision standards, and will perform properly if certain steps are taken by the technician making the installation. Following is a list of possible causes for a remanufactured engine to fail early in service, and suggested procedures to prevent failures. When a properly remanufactured engine fails to give satisfactory service, it is usually due to:

  • Burning piston heads caused by detonation, pre-ignition or “lugging”;
  • Piston scuffing or seizing usually caused by overheating or excess fuel;
  • Bearing and crankshaft wear caused by under lubrication, dirt or coolant seepage.
  • Excessive piston and cylinder wear caused by dirt, ineffective air filtering, coolant seepage or excessively rich, air-fuel ratio.
The customer and Baril Engine have a mutual interest in this engine. We both want it to perform and provide a long, uninterrupted service life.

We recommend these precautions:

1. Before starting the engine, be sure to prime the oil pump with clean engine oil. Fill oil lines and oil filters with oil using an auxiliary pump, operating the internal oil pump with a hand drill, or an external pressure tank. Connect the pump/tank to the oil pressure gauge or sending unit fitting. It is desirable to fill the crankcase in this manner. If using an air pressure tank, be sure it does not run out of oil and blow air through the oil galleries. Air entering the oil galleries defeats the purpose of pressurizing with oil.

  • Do not use synthetic motor oils during break-in procedure. 
  • Use a high zinc additive for flat tappet camshaft break-in procedure.

2. The proper air-fuel ratio is vital in today’s engines. Be sure, the carburetor or fuel injection system has been remanufactured to manufacturer’s specifications and all adjustments are verified. This is especially important on vehicles with modified air intake and fuel systems. Manifold and cylinder head mating surfaces should be checked and in good condition (resurface manifolds if necessary). Be sure the cylinder heads and manifolds are torqued and retorqued in proper sequence if required. Air seepage can cause a lean air-fuel ratio which causes detonation. Check fuel pump for proper pressure and flow.

3. Ignition or diesel fuel injection system should be properly serviced or calibrated and engine timing corrected. Proper valve lash or clearance is very important and requires verification after initial engine start-up.

4. Be sure to use spark plugs of the correct heat range and gap as specified by the engine manufacturer. Check electronic sensors and sending units for proper operation. Vacuum lines must be properly routed and connected to the appropriate fittings to ensure operation of emission control devices and related engine controls and sensors.

5. Check the exhaust thermostat control (if equipped and commonly called a heat riser) to be certain it is free and operating properly. Check the exhaust gas recirculation valve (EGR) for proper operation. Clean the intake manifold to remove deposits from all of the various passages.

6. Rebuild or replace the radiator and hose lines to ensure they are free from deposits so that the cooling system can function properly. Restrictions can cause overheating. Thermostats should be checked or replaced with one of the correct opening temperature. Use the proper pressure cap as specified by the engine manufacturer, and make sure it is properly seated.

7. Important – replace all filter elements. Thoroughly check engine accessories which are to be reused. Clean them internally and externally before installing.

8. The coolant used should be compatible with aluminum engine components and blended to a mixture of no more than 60% antifreeze and 40% water. We recommend that a good sealer with rust inhibitors be added to the cooling system. This will tend to prevent rust and scale deposits and guard against coolant seepage.

9. Before releasing the engine for regular service, verify the air-fuel ratio. Caution the driver against “lugging” and driving at a high rate of speed.



1. Before starting the engine for the first time, be sure it has been properly pre-lubricated, verify the correct oil and coolant levels. Do not overfill the oil level as this can lead to excessive foaming and related bearing damage.

2. Never use a synthetic motor oil for an engine’s break-in and, as much as possible, limit the time the engine is run at idle speed. 

3. Never add cold water to the cooling system while the engine is running. The engine should be allowed to run at normal operating temperature, add hot water/antifreeze if coolant is required.

4. Start engine and run at approximately 1,500 to 2,500 RPM, check the oil pressure and observe for any external fluid leaks. If leaks are detected, repair now. Run the engine for 30 minutes even though coolant may rise to operating temperature in a few minutes. Adjust tappets, if required, carburetor and ignition timing. If the coolant should start to “boil over,” stop engine and allow to cool completely. Then start again and proceed as above. This hot-cold procedure may be required several times to fully bleed all air from the cooling system. 

5. When required, re-torque cylinder heads and manifolds to engine manufacturer’s specifications in proper sequence. Re-adjust tappets if necessary.

6. Start engine again and make a test run on the road at 30 MPH in “drive” range or select the proper gears for standard transmission. Periodically accelerate to 50 MPH and decelerate rapidly. Repeat this procedure at least 10 times. For a large truck or industrial engine, accelerate in intermediate gears as above.NOTE: Applying loads to the engine for short periods of time causes increased ring pressure against the cylinder walls and helps to seat the rings. This is especially important because you are “breaking-in” the engine with heavy duty oils. The rapid deceleration increases vacuum and gives extra lubrication to the piston and ring assemblies.

NOTE: Applying loads to the engine for short periods of time causes increased ring pressure against the cylinder walls and helps to seat the rings. This is especially important because you are “breaking-in” the engine with heavy duty oils. The rapid deceleration increases vacuum and gives extra lubrication to the piston and ring assemblies.


Passenger Cars: Drive normally but not at continuous high speeds or under heavy loads for the first 500 miles. Change oil and filters after the initial 500 miles.

Trucks: Operate the vehicle with light loads up to 500 miles and avoid “lugging.” Occasional acceleration and deceleration in proper gear during this period is advisable. Change oil and filters after the initial 500 miles of service.

Industrial Engines: Follow the above instructions and operate under partial loads for several hours. Change oil and oil filters after approximately 20 hours of operation. Retorque bolts as required by the engine or gasket manufacturer, or immediately after 1000 miles or 40 hours of service, retorque cylinder heads and manifolds to proper specifications if information is unavailable. Also, readjust tappets where required. We suggest tappets be done again after 5000 miles. We know that this means extra work, but it assures long and satisfactory engine performance.

4-Stroke Marine Engines: For the first 20 hours of operation always allow the engine to warm up before accelerating under load and avoid carrying or pulling heavy loads for this time period.

• For the 1st hour, do not exceed 2000 RPM and vary the RPM constantly.

• For the 2nd hour, do not exceed 3000 RPM

• For the next 5 hours, do not exceed 4000 RPM

• After the first 10 hours of operation, change the engine oil and oil filter, and make any necessary engine adjustments.

It is important to vary the boat speed and not run the engine for long periods during the break-in. After 20 hours of operation, the engine may be operated at any RPM within the manufacturer’s recommendation.

2-Cycle Break-In:

The first 10 hours of operation

  • Double your oil with a major manufacturer TCW-3 Oil.
  • Use 92-94 Octane Fuel from a major manufacturer.
  • Do not use fuel with alcohol as an additive.
  • Avoid continuous full throttle operation for the first 10 hours of operation.

1. Start the engine and let it idle, occasionally blipping the throttle for four to five minutes. Liquid cooled engines require that the engine be brought gradually to normal operating temperature to avoid cold seizure resulting from pistons expanding faster than the cylinder liner. Allow the engine to cool completely. Repeat this heat cycle process four more times.

2. Warm up the engine again and drive for five to seven minutes at a very easy pace. Vary the rpm, and do not drive at one speed. Do not run at more than 1/3 throttle or more than 1/3 rpm. Let the engine cool down completely and repeat the initial break in drive. Let the engine cool down.

3. Check the base and head nuts for proper torque. Check the coolant level and add coolant as necessary (closed system).

4. After gradually bringing engine to normal operating temps, operate engine in gear at approx. 1500 RPM for 20 minutes.

5. Operate in gear at no more than 3000 RPM for the next 60 minutes.

6. Cruise at 3/4 throttle or less for the next 4 hours, occasionally reducing throttle to idle speed for a cooling periods.

7. During the final hours of break-in you can operate at full throttle for periods of 2 minutes or less.


  • Use only enough throttle to plane your vessel and then throttle back to below 3000 RPM.
  • Avoid operating in the 3000-4000 RPM range at all times during the 10-hour break-in period.
  • During the 6th hour of break-in, plane boat quickly and then throttle back to maintain minimum plane speed.
  • During this 6th hour, you can throttle up to 3/4 throttle for 1-2 minutes, then return to minimum planing speed.

Carefully following these instructions will aid in the proper break-in of your rebuilt powerhead assembly.


Do not use synthetic motor oils during break-in procedure. Follow the recommendations of the engine manufacturer for the proper viscosity and type of oil to be used during and after the “break-in” period. 

It is important to use oils which contain an EP (extreme pressure) additive right from the start. Special “break-in” oils can be used if recommended by the manufacturer. Older engines without oil filters may require special considerations, such as the use of non-detergent oils unless otherwise specified by the manufacturer.

Consult the owner’s or service manual for the latest manufacturer’s recommendation on oil selection. See the accompanying information on the type of engine oils currently in production and available for use with today’s engines.

This information is provided from the best available sources, however, Baril Engine and AERA do not assume responsibility for data accuracy or consequences of its applications. Please be aware that this pamphlet is not a warranty. Please see your written Baril Engine’s warranty or find it at for any applicable warranty deals.