
MARINE 350 LONGBLOCK
ATK Core Return Process
JEGS and ATK appreciate your business and want to ensure that your core return is as smooth as possible.
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Engine Break-In Procedure
Use or break-in oil or conventional (non-synthetic) multi-viscosity oil with zinc additive for the first 30 hours of operation. Avoid hard acceleration for sustained periods. Periodically change the engine speed to help seat the rings. While the engine is running, be sure to check oil pressure and coolant temperature, and check for fluid leaks, such as oil, fuel, and coolant/antifreeze. Also listen for any unusual sounds. Should you hear an unusual sound, shut the engine off, check for the source, and correct it.
Engines with flat tappet cams only - Start the engine and bring it to 2,000 RPM. Get the engine running smoothly. Then vary the engine speed from 1,800-2,200 RPM in a slow acceleration/deceleration cycle for 30 minutes. This is necessary to provide adequate oil splash and lifter rotation to properly mate each lifter to its lobe.
After 30 hours of operation change the engine oil and filter. For flat tappet cam engines, continued use of oil with zinc or a zinc additive for the life of your engine is recommended.
![Break-In Oil, 10W30 [1 Quart, 32 oz.]](https://www.jegs.com/images/mini_200/500/555/555-28067.jpg)