Der Sportwagen

May / June 2015 14 TECHNICAL EDITOR By Karl Wilen P orsche's watercooled engines since 1997 (US) have continued to be a mystery to many people on their design and function due to the vast differences that exist between a more commonly designed engine. We all know about the intermediate shaft bearing issue, but not a lot of people understand what that bearing is, where it resides in the engine, or what it does. I thought a little engine refresh project would help illustrate the internals of these engines, after all, most people are visual learners. I'll break it down into a couple articles, depending on how much I ramble on. What this article is not, is a full documented engine rebuild, ie, there are a lot of steps I don't have the time or space to show, but rather want to just illustrate the general assembly of the engine. In fact, the factory manuals are incorrect in the proper assembly of the engine in many instances, so keep that in mind. We are starting with a 2.5L 1999 engine out of a Boxster, though the differences are slight between 1997 through 2008 between the M96/M97 engines, with the biggest differences being the variocam design and the intermediate shaft bearing design. In the case of this engine, I have done a full teardown on a good running spare engine in preparation of refreshing it as a backup engine for a SPEC Boxster. There is a big difference between rebuilding an engine that has had a component fail, and a more simple refresh as in this case. If something has failed, the parts components you will be having to replace will be much higher and more expensive. So the idea is to go from a pile of parts, to a long block like this: (This is a 3.2L long block that we built down at Jake Raby's place a few months ago) So we start with a crankshaft bearing housing on the left, and a crankshaft on the right of which I have already assembled three of the connecting rods on. This design is much different from most engines in that the crankshaft inserts into this carrier which houses the main bearings, which then is installed in the engine block halves, versus a more common engine where the crankshaft drops right into the engine block/halves, rather than having a separate carrier. Photos by Karl Wilen Not As Easy As JUST ADD WATER

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