What's the difference and how bad would it be if all four plugs were the same kind?

Or would they not fit or cause immediate engine failure?

I have a feeling that the guys who sold me my FC might not have known the difference.

-Goofy

 

They fit fine. If I remember correctly trailing is a hotter plug.

 

So what could go wrong if all four plugs were the same?

 

It might detonate on a hot day at high speed. But I doubt it. I usually run bur7's all the way around on mine.