Quote:
Originally Posted by phunt
Deck height is the distance from crank center line to top of block. For Porsche, center line of crank, case mating surface, to top of cylinder (head mating surface). Porsche case is 112.5 (112.4) from crank center line to top of cylinder spigot cylinder is 85.3 (85.4) total 197.8 That is deck height. To figure piston below (or above) deck simply measure. 3.0 crank is 70.4 take half of that 35.2 add that to rod length 127.8 then ad compression height of piston 34. That stack or length is 35.2+127.8+ 34 = 197 so if block hasn’t been machined and your running stock piston rods etc then there is built in a .8 below deck piston clearance. Which is what you want Measure your case and cylinders and compare to your rod length and compression height of the piston. Done. Now clay is a good idea for valve to piston clearance
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This is exactly how you measure the difference between the block deck height and the piston deck height, in theory. However, ALWAYS recheck on the engine. In this Porsche work, as in almost all the production engine world, repairs are done to repair and often never repaired to spec. As an example, I have never seen a set rods that have been repaired in the past, having the same CCL. Case deck heights may not be as they were originally either and Cylinder heights do differ as well.
Measure the piston deck height across the pin axis so you remove any piston rocking motion.