SECTION E Cylinder Head CYLINDER HEAD MAINTENANCE The  number  of  hours  run  has  no  bearing  on  when  to overhaul  the  cylinder  head  on  the  4.236  marine  engine as  carbon  beyond  a  superficial  coating  does  not  form and  accumulate  on  the  cylinder  head  and  pistons  as  is the case with a petrol engine. Ease  of  starting  and  performance  are  the  determining factors,   therefore   the   cylinder   head   should   only   be removed when it is absolutely necessary. Before   commencing   to   overhaul   the   cylinder   head ensure  that  all  joints,  gaskets  and  parts  expected  to  be required are available. To Remove the Cylinder Head 1. Drain  coolant  from  heat  exchanger,  cylinder  block and exhaust manifold jacket (See engine photographs for location of drain points). 2. Disconnect   the   battery   terminals   to   eliminate   the possibility of a short circuit. 3. Disconnect   the   exhaust   pipe   from   the   exhaust manifold.    Blank  off  the  end  of  the  exhaust  pipe  to prevent objects being dropped into it. 4. Disconnect  sea  water  inlet  and  outlet  connections from  heat  exchanger  and  exhaust  manifold  jacket, and  connection  between  heat  exchanger  and  fresh water pump. 5. Disconnect the lub. oil pipes from the lub. oil cooler. 6. Remove   the   heat   exchanger   securing   setscrews and withdraw the heat exchanger. 7. Disconnect  and  remove  the  atomiser  leak-off  pipe assembly.    Blank  off  the  ports  on  the  top  of  the atomisers. 8. Remove  the  fuel  pipe  from  the  fuel  filter  to  the  fuel injection pump inlet, also the fuel pipe from the fuel filter to the fuel injection pump outlet.  Blank off the exposed parts. 9. Disconnect   the   fuel   pipe   from   the   fuel   lift   pump outlet  to  the  fuel  filter.    Remove  the  two  setscrews which secure the fuel filter to the cylinder head and withdraw the filter from the engine. 10. Remove    the    breather    pipe    from    between    the cylinder head cover and the induction manifold. 11. Disconnect   and   remove   the   high   pressure   fuel pipes  from  the  fuel  injection  pump  and  atomisers. Blank  off  the  exposed  ports.    Release  and  remove the    nuts    securing    the    atomisers    and    carefully extract  the  atomisers  from  the  cylinder  head  (see Fig. E.1). 12. Disconnect  the  fuel  pipe   and  electrical  lead  at  the thermostart unit. 13. Remove  the  air  filter.    Remove  the  induction  and exhaust manifolds. 14. Detach    the    rocker    cover    from    the    engine    by removing   the   four   screws   which   secure   it   to   the cylinder head. 15. Remove the four rocker  bracket  securing  nuts  and washers, and remove the rocker assembly from the cylinder   head   (see   Fig   E.2).      Remove   the   push rods. 16. Release   and   remove   the   cylinder   head   nuts   or setscrews   in   the   reverse   order   of   the   tightening sequence shown in Fig. E.1). 17. Remove    the    cylinder    head.        Do    not    insert    a screwdriver  or  any  other  sharp  instrument  between the cylinder head and block.  When removed place the   cylinder   head   on   a   flat   surface,   preferably wood, to avoid damage.