Originally Posted by
rollerrocker I,ve been fitting cometic mls head gaskets dry for some time on prexflow race engines and my twincam race engine. No problems at all. Until a few weeks back.
I was building up a twink,I always water test the TC engine before timing the cams up and fitting the sump,water started leaking down the oilway which feeds the head/cams.
I pressured the system 10lbs approx. and water was seeping out the gasket along the side of the block.
I removed the head thinking I'd got some crap between the surfaces.When I removed the gasket it was wet all over indicating that the gasket was not sealing round the waterway holes. Hmmmm.
The thing that I noticed was, on the twink head the oil passage is offset and is linked with a small well .When studying the gasket, which are designed for crossflows, the oval bolt/oil hole has a raised lip to seal oil pressure. This lip does not correspond with the well in the head,hence the water was tracking from between the layers of the gasket to the oil hole.
I've recently done alot of work involving head surface finishes and am sure my machining meets the 50Ra requirement.Certainly had no problems on prexflow engines.
After alot of head scratching and asking around people in the know,nobody had ever encountered the problem before.
My solution? Fitted an Ajusa competition gasket. Pressure test showed no leakage at all. Time will tell.
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