Flying the new Cub Engine

The only real gripe I have had with my Piper J3 Cub was its climb capability, especially with a passenger aboard. It has always leapt off the ground, but once in the air it would climb very slowly. So slowly with a passenger, that it was a little scary for fear of losing the engine at a bad time.

Today we finished the installation by safety wiring the prop and running up the engine. For the first run-up we tied the plane to my truck, since the brakes on a Cub would never hold the plane at full power. It was also a precaution, in case there was an issue with the throttle. Before starting the engine, we had to prime the oil pump by spinning the prop with the bottom spark plugs removed until we saw oil pressure.

Once everything was set up, verified and secured, we began the process of starting the plane. I sat in the cockpit to hold the brakes while my mechanic propped the plane. With everything new and tight we expected the engine to be hard to start. It was. Once we got it going though and verified oil pressure, it was a great sound. Once the oil was warmed up, we ran it up to full power. It was obvious that there was much more power than the old engine. This one pulls 200 rpm more than the old one. One of my concerns was that my prop would need to be re-pitched to keep the RPMs below the red line for the engine. I still have a margin. After the run-up we shut down and put the cowling on the plane. It was time to fly.


Taxiing out to the runway it was interesting getting used to the new sound of the engine idling. It has a very different sound from the old one. The wind was calm and the sky was clear. Perfect. I did another pre-takeoff run up, and I taxied onto the runway. As I advanced the throttle, everything felt normal until about halfway to wide open. There was a rush of power that I had never felt in the Cub. It leapt off the ground as usual in about 200 feet, but instead of slowly climbing out, it was really climbing nicely. I was at pattern altitude by the time I was ready to turn downwind. There was never a question of making it back to the runway if there had been an issue. I climbed to 3,000 feet and hovered over the airport for about 20 minutes. The oil temp and pressure were stable so I decided to see what kind of climb it had beyond 3,000 feet. I took the plane up to 7,500 feet. It would have taken most of a tank of gas to get to 7,500 feet with the old engine. After 45 minutes, I started down. This engine upgrade has really given the Cub a new and interesting capability. Wahooo....