Crate Engine Break-In Procedure

Start with an Inspection

Before you start the engine, ensure that all accessories, such as the headers, alternator, and power steering pump, are tight and check for any water or oil leaks. Even if your engine came as a complete, turnkey assembly, it’s best to check all major components such as the distributor, spark plugs, ignition wires, carburetor. These items could have been damaged or disturbed during shipping.

Lubrication Considerations

When installing an oil filter, fill it about halfway with oil, lube the rubber gasket the surrounds the filter with oil, and then tighten by hand. Consider using a premium brand oil filter—a cheap filter will not be cheap if it costs you an engine. You will need to fill the engine with oil as they are shipped dry. Use a high-quality break-in oil like Maxima 10W-30 or 15w-50 or Driven BR (15W-50) or BR40 (10W-40) or other name brand break-in oils, especially with flat tappet camshafts.

Engine oil coolers

If you have an aftermarket or factory style oil cooler you MUST replace the cooler and lines with a new assembly. It is impossible to thoroughly flush the oil coolers. You may also eliminate the oil cooler if desired.

Prime the Pump

To avoid dry start-up, it is best to prime the oil system with an engine-priming tool or a pre luber. The engine is assembled with assembly lube and pre-lubricant, but always consider priming the oil before start-up.

Use Conventional Wisdom

Even if you plan on running synthetic oil, you should break a new engine in with a conventional, mineral-type engine oil for the first 4,000-plus miles. If you fail to follow this procedure, the piston rings may never seat.

Change Oil Often

On freshly built engines, you’ll need to change your oil and filter much more frequently. After using a break-in oil, you should change your oil at 50 miles, 500 miles, and 1,500 miles. Again, at 4,000 miles or so, it’s fine to switch to a synthetic oil if you choose.

Timing is Everything

Set the ignition timing after starting the engine. The starting point for most carbureted engines is 34 degrees before top dead center with vacuum advance disconnected at 3,000 rpm. Some experimentation with timing is required for optimum results with locally available fuel, but it should be between 32-38 degrees BTDC. Base timing at idle is usually around 10-12 degrees before top dead center.

Take Care of Your Flat Tappets

If your engine uses a hydraulic flat tappet camshaft, keep the engine between 2,000 and 2,500 rpm, with no-load on the engine for the first 30 minutes. This is critical to break-in the camshaft, although roller cams really do not need to follow this step.

Keep Your Cool

Most often, the cooling system on a fresh engine swap will have a lot of trapped air, which will lead to wild temperature gauge readings and possible water pump cavitation. To help alleviate trapped air in the cooling system, fill the cooling system with a 50/50 mix of quality coolant and water a few hours before you plan on starting the engine. Leave the radiator cap off during this time. This tends to help purge a fair amount of trapped air before you start the engine. You can also use a lever-vent type radiator cap on your radiator so you can manually purge trapped air while the engine is running. Your normal cap can then be re-installed after the engine cools off.

Vary the Load for Initial Break-In

For the first 200 miles, drive the vehicle with varying speeds and loads on the engine. Occasional full throttle runs from a rolling start (2,000 rpm or so) to 4,500 will help seat components such as piston rings, but the engine should be cooled after doing this. Also, it is wise to check rocker and valve clearance after 150-200 miles to insure adjusters are tight and lash is proper. Re-check again at about 500 miles.


After two or three days please re-check all fluid levels.

Break-In Plan

Although it is not necessary, the following procedure will help speed up the break-in process:

  • Make five or six medium-throttle accelerations to about 4,500 rpm before letting off in gear and coasting back down to 20 miles-per-hour.
  • Run a couple hard throttle accelerations up to about 5,000 rpm and once again coast back down to 20 miles-per-hour.
  • Let the engine cool, change the oil and filter, and check the coolant level.
  • Drive the next 500 miles normally, keeping the engine below 5,000 rpm and minimizing operation at idle.