Re: stag heads skimming limits

[Glenn Merrell <gmerrel@domain.elided>]

Hello Hew,
	The minimum cylinder head thickness is 4.427 inchs, measured from the bottom of
the cam shaft bore to the cylinder head surface.  Measure it with an 8"
precision caliper, a gauge block and measuring slab, or a 5" outside micrometer
and a ball bearing placed in the bottom of the camshaft bore, subtracting out
the diameter of the ball bearing.  This measurement method and distance is
according to a Technical Notice dated March 11, 1975.
	The cylinder head trueness should be kept to less than 0.0005 inch throughout
(less than 5 ten-thousands).  The reason for this is when you torque the
cylinder head, the head will bow or twist across its length when measured  at
the camshaft bearings.  If the cylinder head bows or twists like this, the
camshaft bearing surfaces will wear rapidly, causing loss of oil pressure to the
camshaft bearing surfaces after only a short period of time.
	Standard Stag headgaskets measure 0.055 inch, extra thick gaskets measure 0.080
inch.  Extra thick gaskets will perform quite fine.  The purpose of the estra
thick gasket it to raise the cylinder head up high enough so the valve will not
impact the pistons when in the closed position.  Valve timing must be exactly
right.

Regards,
Glenn  Merrell
Triumph Stag Register USA VP

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