Tweaking the valves
QMy Isuzu 42 4LC1 engine has reached the 1,000 hours recommended for checking and adjusting the valve clearances. I have been told the rocker box cover has a rubber gasket. Is this true or does it require a new cork or paper gasket? Is there a workshop manual available for this engine?
For the manual look at wincogen.com/files/ downloads/winco_engine_maintenance/isuzu_4le1_opm.pdf or chat to a hire fleet operator or Isuzu industrial/agricultural engine dealer. The manual will almost certainly be for the base engine, not the marine version. Almost all modern engines use a rubber gasket.
Adjusting the valve clearances once you know the clearance is simple. Turn the engine over until one valve is fully down. Mark the engine pulley (the lowest one). Use the mark to allow you to turn the engine over one full turn (give or take an inch or so). Adjust that valve. Rub out the mark and start again with another valve. This will work on any engine with any number of cylinders and any valve arrangement.