Sunday, October 21, 2007

M249, Part 2: The story of the VW 1500's most misunderstood option gets more interesting

Aaron Britcher and I have been corresponding since my post on US-spec VW 1500s and option M249. He owns a 1965 model 1500S notchback that was specially ordered by an Australian dealer with a number of factory options including M249 -- a velvet green model 312 (RHD) that was delivered to Adelaide in November 1964 and used as a demonstration car by the dealer. Aaron was puzzled, though, because while his engine has the "M-249 90-OKTAN" plate on the crankcase breather stand the case isn't stamped with an N. VW in Germany confirmed that the engine is the one that came with the car, and when he tore it down for an overhaul he found the expected flat-top cylinders. Was the lack of a letter stamp a production error? Or was VW's documentation of M249 even more inconsistent than we had thought?

Neither, as it turns out. Aaron did some research and was able to find the answer in his copy of the VW Workshop Manual, which has an addendum with a surprising amount of information about M249. The engine cases were stamped with a letter only beginning on February 18, 1965 (chassis no. 315 124 961 / engine no. 0 878 040) and through the end of the model year in July -- R indicating 1500S domed pistons and N for M249 flat-top pistons. Another surprise was to learn that 1500N engine cases were also stamped beginning on the same date (at 315 125 092 / 0 867 737) -- with the letter K, confusingly -- to indicate dished low-compression pistons (M240). I guess this means an engine with no letter stamp from late in the 1965 model year was a standard 1500N.

Also surprising and very welcome is this full page of technical and performance data for the 1500S M249 engine, which among other things confirms that even 1500S Ghias could be ordered with M249:

So, the final word: only VW 1500 engine cases built between late February and August of 1965 are stamped with the identifying letters N, R, or K. Any photos of these VW 1500 case stampings would be much appreciated, so send them in if you have them.

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