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Cam Timing

by Norman Nock

Originally published in the Austin-Healey Magazine, January 1998



The pictures in the service manual show the engine in a vertical position, but when a mechanic is rebuilding the engine, he has the block on a bench or engine stand, usually upside down.


Following the service manual, it would be easy to install a cam chain with the cam timing backwards.


When this happens there will be a lack of power with ignition timing set correctly, however, when the timing is over advanced the power returns, but at high speed the power falls off again.


Here is a basic way to check if you suspect your cam timing is out. If you have a four cylinder engine, use rocker 7 and 8 to give "working clearance" to number 2.


Check Valve Timing


  1. Remove the rocker cover.

  2. Adjust the rocker clearances of numbers eleven and twelve valves to O.120 in (3.04 mm) to give a working clearance. NOTE: This clearance may vary according to the lift of the camshaft employed. The clearance should be sufficient to enable feeler gauges of reasonable thickness to be inserted when the valves are on the 'rock'.

  3. Turn the crankshaft in the normal running direction until number one piston is at T.D.C. on the compression stroke, indicated by the mark on the crankshaft pulley coinciding with the pointer on the timing cover.

  4. Check that numbers one and two valves are fully closed by ascertaining with a feeler gauge that clearance exists between the valve tips and rocker pads.

  5. Using two feeler gauges of the same thickness check that the rocker clearances of numbers eleven and twelve are the same.

  6. Oscillate the crankshaft to achieve this condition. Ensure however that when the rocker clearances are the same the conditions in instructions 3 and 4 are maintained. NOTE: The actual rocker clearance is not important providing the clearances are the same.

  7. Should the valve timing prove to be incorrect, retiming will be necessary.

  8. Reset the rocker clearances of numbers eleven and twelve valves.

  9. Refit the rocker cover.

Not what you were looking for? Don't forget you can check our back issues using the AHCUSA Magazine Index.


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