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The Porsche 908 is a vintage engine that spans time, history and imagination. So with all of this in mind, when we were first approached by the customer to repair this engine block we were understandably nervous. Welding magnesium is not an easy task.. Like aluminum, magnesium comes with a whole host of problems. A major problem with both metals is porosity. Porosity traps and holds dirt, oils, combustion residue and anything else that is able to make its way through the engines oil system and into the engines crankcases. This residue of foreign metals and chemicals will re-appear and bubble out into the welding puddle quite inconveniently. The welding of these metals is not for the impatient or faint of heart. This job is for experts only!

We commenced the project with an inspection of the cases and a discussion of particulars which evolved quickly into a procedural plan of action. One or our first tasks was to make a set of steel plates in order to keep the cases flat so that they will not flex, twist or warp under the heat and stresses imposed during welding. We made up a top and a bottom plate for the cases from half inch steel plate. After the machining of the slots and bolt holes the plates were then Blanchard ground flat. The inside or mating surface plate had slots machined into it for welding access. The outer plate had holes machined the size of the cylinder bores for access to that side of the case. Matching holes were machined into both plates strategically placed at the main saddles holes to allow mounting bolts to go through the cases and attach the inner and outer plates. As should be obvious by now, this is not a shade tree or job shop project.

We cleaned the cases with soap and hot water, dried them off and then put them in an oven at a medium but steady temperature. The object of this was to try and boil out as much of the remaining oils and errant chemical residue in the cases before we started welding.

With the cases now as clean as we could get them and the plates fully machined and ready to bolt up, the welding commenced.

It should be quite obvious that this is a complex job. So why all the bother? Because these are some very unique and historic engine cases. The Porsche 908 was born of a political decision by the FIA, post 1968 Le Mans to limit engine size to 3.0 liters. The engine is a flat eight cylinder two valves per combustion chamber, chain driven DOHC, fuel injected, air cooled power plant. The engines cases are magnesium as previously mentioned while the chrome plated cylinders and cylinder heads are aluminum. The connecting rods were titanium with a compression ration of 10.4:1. The valves were set at a rather wide 71 degrees to get cooling air between them.

The 908 won its first race but it had its share of teething problems.