The days when K&B and some other engines had the exhaust stack on the left hand side so they'd spit in your face if sidewinder mounted on a ccw flying profile? My oldest Fox is a .15 from about 1960, that's probably powered 12 planes. The oldest K&B I've used is a Stallion 35 I bought about 1969, when they were going for about 6.98, to compete pricewise with the McCoy RH .35. Has probably 700 flights on cl and on a SAM competition Spook 72. I'd use the K&B for competiton and competition practice, and then swap with an OS 35 III rc engine for sport flying. The K&B had noticeably more power. Starting to loose compression and leaking around the cylinder base.

I just about finished replacing the crankcases on my Fox 35 Stunts with the newer crankcases so I can use bolt-on mufflers.

When I returned to RC in 1978 with my first good proportional outfit, I used that almost 20 year old Cub .099 on a Jr. Fledgeling with a Cox 2 channel rig. After staggering around the air for a few underpowered flights, I put on a Cox Golden Bee .049, and had much better flying, till a large boulder jumped out of the ground and hit the plane.