Came across this in my toy box. It is stamped 40 RR, has a pressure tap and a .440 diameter intake.

Note also the bizarre exhaust deflector.

At first I thought it was a homemade and restamped 40 RC but the gold label on the box says H40/RR.

I had no idea OS made a purpose built rat motor.

Have at it!!

Bob Z.

Instead of selling it, I'm donating it, along with about 600 other engines, to the Brodak museum. 

I feel that our CL history should be public domain and available to all who are interested.

Selling it would either sequester it to a private (possibly overseas) collection, keeping it from the public eye.

Or, worst yet, some could buy it only to turn it for a profit.

The only engines that I will release for sale, both from my accumulation and John's, are the ones where we have multiple examples (and there are hundreds of them)

Bob Z.

That's the Rat Race engine (hence the RR) and has a single rear ball race. The 40P (rc pylon) had twin ball races and a different prop driver. The 40S was also single ball race for stunt. Early OS 40's with no letters were single ball race for sport RC. These were all phased out with the later (common) H40 which had a much more bulbous transfer passage, twin ball races, different bore and stroke and AFAIK were only RC.

I'm thinkin' it's very odd that this one doesn't have any "OS MAX" ID on the bypass. It may have been taken off by a previous owner, for reasons unknown. Some folks had a warped idea of what a "hop up" involved! Steve