Following on from the oil service at the weekend one of the things I didn’t get round to doing was checking the tappet clearances. This little task is an integral part of any service and only takes about 30 minutes but time wasn’t on my side.

The objective is to ensure the gap between the top of the valve stem and the underside of the rocker arm tappet is set to a prescribed distance… in this case 0.010” (0.25mm)

Insufficient tappet clearance will result in a given valve not fully closing and will lead to early opening. Too much tappet clearance, will lead to “lost motion”. This means that as the cam tries to open the valve; the push rod and rocker arm must first take up the “slack” in the excessive tappet clearance.  The result is late and insufficient opening of the valve and early closing.

Due to the principals of thermo dynamics a lot of motor manufacturers stipulate a tappet clearance for a hot and cold engine. Land Rover however only provide a single value for hot and cold. Wonder why….

First of all, the air cleaner and pipe has to be removed… 1 wing nut, 2 jubilee clips


Then the rocker cover… 3 bolts


The valve train… Beautiful eh?


Using the rule of 9 and counting the valves from the front of the engine…

  • Check No. 1 valve with valve No. 8 fully down
  • Check No. 3 valve with valve No. 6 fully down
  • Check No. 5 valve with valve No. 4 fully down
  • Check No. 2 valve with valve No. 7 fully down
  • Check No. 8 valve with valve No. 1 fully down
  • Check No. 6 valve with valve No. 3 fully down
  • Check No. 4 valve with valve No. 5 fully down
  • Check No. 7 valve with valve No. 2 fully down


Loosen 1/2” lock nut. Adjust tappet with flat head crew driver until the feeler gauge is a “sliding fit”. Tighten lock nut. Re-check the gap.


I also remove the spark plugs so I’m not working against engine compression but its still a bit of up and down even with the hand crank.


Lastly, replace the rocker cover, the oil bath air filter and hose and reconnect the vacuum advance pipe to the carburettor.

Nice little midweek evening job.