Cleaning the Engine Block

PROCEDURE

1. Remove the main bearing caps and remove the bearing shells from the caps and the block. Tag the shells with tape to match their bearing positions (bearing number, block/cap) and set them aside.
2. Scrape all traces of the old gasket material from the mating surface of the block. Be careful not to leave any gouges.
3. Remove all covers and threaded plugs of the oil galleries from the block. The plugs are usually very tight, so it may be necessary to drill them out and then repair the threads in the hole. Replace the plugs with new ones during assembly.
4. If the engine is heavily contaminated externally, take it to an automotive service shop for steam cleaning or thermal cleaning.
5. After the block is returned from the shop, thoroughly clean all oil holes and galleries again. Special cylinder-shaped brushes of a special shape are available for this purpose (ask at automotive accessory stores). Rinse the cavities and passages with warm water and continue rinsing until clean water flows out of the opposite side of the block. Dry the block thoroughly, then lightly coat all machined surfaces with clean engine oil to protect them from corrosion. If compressed air is available, use it to speed up drying of the block and to blow out hard-to-reach cavities and passages.

Always wear safety glasses when working with compressed air!
6. If the block is heavily contaminated or has scale deposits, clean it with a brush using hot water and soap. Do not try to save time by cleaning the block carelessly. Regardless of the method used, make sure hard-to-reach cavities, passages and holes are thoroughly cleaned. Finally, dry the block and lightly coat the machined surfaces with clean engine oil to protect them from corrosion.

7. Run a tap of the correct size through all threaded holes in the block to ensure that the torque wrench readings match the actual clamping forces when assembling the engine. If possible, blow out the tapped holes with compressed air, removing all fine debris and chips. After cleaning the holes, run a thread chaser over the threaded part of the bolts.

8. Install the main bearing caps in place and hand-tighten their bolts.
9. Coat the threads of the new plugs with non-hardening sealant and seal the oil gallery openings with them. Make sure the plugs are tightened securely.
10. If you do not plan to begin engine assembly immediately, place the block in a large polyethylene bag to protect it from contamination.