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Discussion Starter · #1 · (Edited)
When doing a rebuild it is important to ensure flatness of both the deck and the head. It is also important to maintain the chamber volume as this greatly affects the compression ratio and the octane demand of the engine, and thus it’s propension to knock.

Don’t settle for gasket X just because it’s sold by your tuner or part supplier and end up with an unknown compression ratio after your surfaces have been machined: talk to your machinist instead, give them the stock gasket and point them to this page on Cometic.com which lists MLS gaskets of the highest quality available in four different thicknesses.

By measuring the stock gasket and comparing with the available replacement thicknesses, the machinist will know how much material they can remove in total from both surfaces to maintain the chamber volume. On the next rebuild they can compare that gasket with the next available size and so on.
Auto part Circle Metal Event Symmetry

One last thing: the deck and head surfaces must meet very stringent surface roughness specifications, in addition to the usual flatness requirements: surface must meet Ra 30 or better (preferably Ra 20) and this can only be achieved with a diamond cutter. Carbide cutters are great for most uses but not for MLS gaskets surface prep. Don’t ask me how I found out.
 
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