It's a Nelson FIRE (front intake rear exhaust). I have a couple of these and they were not piped engines.
The original application was Combat (F2D) but a bunch of rules changes did them in. They're still good for Rat Racing, Goodyear, Clown Racing, and 15 Profile Carrier.
These engines could easily turn 30,000 RPM or better and still last forever. That's compared to 24,000 and short life on the engines they replaced. The original price was $175 and a bargin considering the performance.