If you study the page on this website ( XPAG Casting Numbers ) that gives you the various casting numbers that are to be found on the cylinder heads and blocks of the XPAG engine, you will note I have added (round hole) and (oval hole) to the description.
This is because Morris Engines improved the water flow in the head on later engines, especially around the exhaust valve’s seat and the reason the head’s then gained long-reach spark plugs (because of the thicker head for the water jacket spaces).
Like all modifications this led to more complications in that there were now two cylinder head gaskets.
To put it simply, you cannot use a round hole gasket on a head or block that has oval water jacket holes.
The folded over edges of the head gasket must be crushed in order to seal; if fitted to an oval hole head or block, or both, the round hole’s edges will be out in the coolant flow and not be gripped.
But you can use the oval holed head gasket on both round and oval holed heads and blocks as its hole’s edges will be crushed by the machined faces.
If, like me, you have an exchange recon-unleaded head with oval holes fitted to a round holed block, the ‘oval hole’ head gasket must be used.
The diagram gives more idea and the casting number list will help you buy the right gasket set BEFORE you lift the head off.
THE ROUND HOLE HEAD GASKET CAN ONLY BE USED IF BOTH HEAD AND BLOCK HAVE ROUND HOLES.
Any other combination, use the oval holed gasket.