I just pulled a set of Bosch HR10BCY plugs out of my fox and replaced them with autolite 2545 gapped at .054. I used E5TE heads as they were in the better condition compared to the set of E7TE as well as ported. I used the plugs that were in there when I got them because they looked relatively new when I was putting the engine together.

The thread reach is concerning me. The bosch have 11.3mm reach and the 2545s have 20.5mm. Were they just the wrong plugs?

Thoughts?