There are a number of unused, threaded holes between the bolts that hold the intake/exhaust onto the head. I need to attach a fuel rail bracket to the engine and I wanted to use a couple of these unoccupied holes. They seem to accept an M10x1.5 bolt; however, it only goes a turn and a half in and then stops. I don't want to force it and strip the threads so can someone confirm what size these holes are tapped to? It's not a 1.25 pitch as that doesn't even begin to thread on.

What holes are you referring to? A photo or two would help.

I circled the two bolt holes I plan on using.

I did not find corresponding holes on the E88 head or N47 (Maxima) head on my cars. Sorry, I can't help you.

Thanks for checking Steve

The fuel injected heads have holes drilled and tapped for both carb intake manifolds and FI intake manifolds. What you're seeing there is the peeking out of one of the FI intake manifold mounting holes.

Here's a (hoovered) shot of the side of a FI head where you can see all of the holes:

So to answer the question about what pitch to use... I believe it is M10 x 1.25. If you can't get that to thread in, maybe the threads are mess up inside the head.

One of the PO's installed a crate 280 engine so that explains the extra bolt holes.