RE: 1.00Lx Blowing plugs (MC-59)
Blowing plugs , 95% of the time, comes from one cause: a lean run.
Fuel foam will get a lean run or temperature spike rapidly. At the power/rpm/frequency/energy this engine puts out, the slightest out of balance will cause havoc. Also, some plastic spinners can distort in shape, causing even more mystery.
If the fuel tank is not 100% isolated from the airframe - instant fuel foam. May not even show up on the ground, and you might not even see the microbubbles. But with an engine unloaded in the air... the problem will become worse and results in a blown plug. Even if you set the engine rich on the ground, you will still have problems. Situation has to be corrected.
Step one is to fix the problem. Since the spinner change caused the problem - seems that is the primary answer. Install a good quality, balanced spinner and prop.
For additional protection to avoid any similar problem, use a bubble-free fuel system. Bubble-Jett fuel tank or a Tetra bubble-free tank. Air and fuel do not mix, no bubbles.
I hope this is helpful
Bob