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Engine Building Fundamentals: Deck Preparation

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Deck Preparation


00:00 - The deck surface of the engine block is critical when it comes to the ability to achieve a good seal from the head gasket.
00:07 The head gasket relies on the surface of both the block and the cylinder head to be perfectly flat for it to be able to function correctly and seal the combustion pressure inside the cylinders.
00:20 It's not uncommon for the deck surface of the block to become uneven or warped particularly if the engine has been overheated or previously had head gasket sealing problems.
00:33 In this case, if no corrective work is performed the new engine will be quite likely to quickly succumb to head gasket failure too.
00:42 The other consideration with machining the deck surface of the block is that the alignment should be parallel to the crank shaft centre line.
00:50 This ensures that the distance from the crank centre line to the deck surface is consistent across all cylinders.
00:58 For these reasons it's common practise when having the engine block machine work carried out to machine or surface the deck of the block too.
01:08 This is also a good opportunity to correct any alignment issues with the deck surface.
01:14 Typically a minimal amount of material measured in thousandths of an inch will be removed from the block surface during this machining process, and really the machinist is simply removing just enough material to achieve a flat surface and remove any high points from the block.
01:32 This process can also be used, however, to make corrections to the deck height of the block and this will influence where the pistons sit in the block at top, dead centre.
01:45 The actual surface finish of the engine block is also an important aspect to consider in order for the head gasket to seal correctly.
01:54 While a machine finish on the deck surface may look or feel smooth, on a microscopic level there will still be a certain amount of roughness associated with it depending on the way the surface was machined.
02:07 If the surface finish is too rough, or surprisingly, even if its too smooth, the head gasket may not seal correctly.
02:16 The head gasket manufacturer will recommend the required surface finish in order to achieve good sealing and this data should be provided to your engine machinist.
02:27 Surface finish is defined by the roughness average, or RA for short, and this is measured using a precision piece of equipment called a profilometer.

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