BMW 502 Race Preperation

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Engine

The stock engine in this model 502 came with 120hp: not bad, but not very exciting. One of the sports versions of this V8 came with 160hp, and was used in the 503, 507, and 3200CS. This engine has bigger valves, bigger ports, higher compression, a hotter cam, and two Solex carbs instead of one. The engine that Don Dethlefson sold us was originally in a 1965 3200CS, and, since that was the last year that the V8 was used in any car, it is essentially the final performance version of the V8. It has an interesting variation that we have been unable to document in any factory literature we have seen. The carburetors on this engine are mounted sideways. That is, compared to all other carbs we have ever seen on any engine, these are turned 90 degrees to the side. They are also of a type unlisted in any of our parts or repair manuals. We were very fortunate that we were able to clean up and rebuild these carbs without needing any replacement parts. 

    Our engine work began with complete disassembly and examination of the parts. Most parts were in excellent condition; but the heads, the crank, the rods, and the block were sent off to Leo Goff at Memphis Motor Werks for machining. Once they returned, all the engine parts underwent extensive cleaning and further critical examination. Once all parts were clean and seemed healthy, a fairly standard, careful assembly was done. 

     Actually, the block itself was an exception to that 'fairly standard' comment, in as much as it is an all aluminum block with pressed-in steel sleeves. We looked at pictures of the BMW factory tool for pulling out these sleeves, as well as a similar Alfa tool, and then Brandon made us a tool to do it. And then he made another one STRONG enough to do it. Another fit of cleaning got the block and sleeves ready for new o-rings and reassembly. The cylinder walls were honed and the crank polished by Leo Goff; we put them together and checked their clearances with plastigage. All the rotating parts were balanced and the rods were reconditioned by Leo also. The stock piston pins were all in bad shape, and Leo found lightweight replacements for them. We assembled the pistons to the rods, installed new rings, put in new rod bearings and replaced the rod bolts. The original rod bolts were identical in size and thread pitch to the bolt used in the modern M10 and M30 BMW engines. The modern bolts use a much higher torque specification, presumably due to metallurgical improvements. We installed the piston and rod assemblies, checked clearances with more plastigage, assembled the cam, new timing chain, oil pump, front covers, oil pan, etc and called the short block complete. 

     The heads were also reworked by Memphis Motor Werks and they now have new seals, a fresh competition valve grind, and a few new valves. The heads were installed to the engine after replacing several damaged head studs, then the oiling tubes, push rods, and finally the rocker shaft assemblies were shimmed and then bolted in place. Intake and exhaust manifolds were finally bolted on and the basic engine was done.

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