Head gasket question

[sandyman]

When replacing a head gasket (if old one not available) do all the channels on the head have to match with the holes on the gasket or is it ok if one or two remain covered or partially covered?

[armyphil]

No they must all match!! Otherwise you could be blocking coolant flow!!

[ridealghp]

When I changed my JX 1.6td head gasket, I noticed that some holes in the gasket were smaller than the cast cooling passages by varying amounts (and in one or two places no hole in the gasket so the channel blocked). I assumed that the engine had been designed with the full size passages, then the coolant flow optimised by varying the sizes of the holes in the gasket. I checked that the new gasket had holes of the same sizes and in the same positions as the old one, they were, so I did not modify the gasket. Maybe an expert will know.