Prep Differences Between SM and ITx

[mossaidis]

Maybe I just wasn’t taking advantage of the rules in IT when I ran an ITA Miata, but my impression is that a built SM motor does not comply with IT rules:

Spec Miata 9.1.7.1.h.2
A valve job will consist of only three flat angles; radius cuts are not allowed. A 45 degree seat angle must be used, which may vary in width from .030 inch to .050 inch. To narrow or correctly position the face angle, a bottom angle of 70 degrees must be used. To narrow or correctly position the face angle, a top cut of 30 degrees may be used. All angles must stay on the cast steel block portion of the seat. The angles must not extend off the seat into the aluminum casting at the top or bottom of the seat.

And have someone who has built a full-on IT car read through 9.1.7.1.f (cylinder head). I never was sure about SM’s unshrouding of valves meeting IT rules, or the reference to plunge cutting in 9.1.7.1.f.3.

Me thinking if IT allowance for "balance and blueprint" in combination of allowable engine tolerances as define in the factory manual applies here. but don't know...