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Final Motor Specs

August 25, 2018

As described in the last post, the motor build is mostly completed. There are a few weird odds-and-ends yet to be done, like a drill and tap for a bolt to secure warm-up regulator to the block and such – nothing major. But I realized that the final build specifications were never discussed fully. So here’s a chart and explanation of my build, comparing it to stock BMW and the Alpina build.

Virtually every decision-point was vetted. Twenty-eight hundred cc displacement was chosen because I wanted to use a turbo-diesel crank (it’s a very stout crack, able to withstand the high pressures of the diesel motor) and I always kinda liked the e30 c2 2.7, based on the same crank and big bore. The pistons were an easy decision, given the crank and desire to get at least 2700cc. I didn’t feel the need for a much bigger bore and knew that several folks had successfully used a 86 mm bore on the stock 325i M20 block.