If the studs are finger tight and there are still a 1/4 inch of threads out of the block, and there is ample room to cut more threads in the hole, is it better to do that or just leave the stud sticking out a little?

Bottom tap the hole.

For a performance build all blind holes in the block should be bottom tapped and then cleaned. Especially any threaded hole used for studs. Buy a set of bottom taps and use them. You'll be amazed how much crud is trapped in those threads, even after hot tanking.

I know that is the common norm, but why exactly? Is it just to clean out the trapped crap, or to gain more thread engagement by cutting deeper threads?

I think I can make a case if the stud is already screwed into its last thread, cutting more threads in a taper tapped existing hole with a bottoming tap will only weaken the block.

The holes are clean. I looked with an endoscope. So you are saying cut more threads and run the studs down to the shank?

If the stud was screwed into it's last thread, why would you cut more threads into the block?

I've never seen a set of ARP main studs, or head studs, screw in all the way without bottom tapping all of the holes. My guess is that ARP designed their studs for fully threaded holes but I don't know for sure. In any case, Mopar blocks need to be bottom tapped if a person is going to use ARP studs.

I'd rather have it engaged all the way into the threads than stopped against the top edge of the hole. A couple threads (1-2) showing out of the hole is normal on all my main and head ARP stuff.

Usually the first three or four threads on most fastener take the load, look at any broken fastener, they stretch in the top threads, not the bottom or in the middle
I would run what you got a long as the threads in the block are 5 or more threads in the hole

That was my question.

as a machinist, i like to use all the threads available.
however, make sure the hole has more [full] threads than the fastener, or a break is almost guaranteed when torquing the fastener to spec.

I noticed that some of the studs rub on the inside of the main bearing cap making it difficult to remove the stud by hand when the bearing cap is seated. I would think this would move things in ways they were not intended to move. Does anyone ever open up the holes in the caps for clearance so the only force exerted on the cap is the clamping force?

Yes, the main caps often need to be reamed out slightly when installing studs. I have a bunch of metric and standard reamers so I can provide clearance while removing the minimum material.

Thank you

If you screw a stud into a tapered tapped hole your creating a stress riser at the point the stud wedges it's self into the taper. This is bad.

Explain, because it seems to me very little force is ever transferred to the end of the stud, in tension.

How many main studs you ever torqued?

They move when you apply load. Jamming into the taper is a wedge.

Isn't the idea to stop screwing in the stud before you get to the taper in the hole?

So, we now circle back to our starting point, one only needs enough threads to top out on the stud's threads and jam(?) the stud, because the studs move under load, and what happens in the female threads beyond the bottom of the stud is of little concern and does not automatically require a bottoming tap.
Have I got this right?

Why exactly, is because you want the threads in the hole deeper then the threads on the stud. Period!
The case you are arguing is what exactly? I tryd to explain to you the stress riser at the bottom is a wedge weekining the cast iron hole if the stud is not fully engaged. It's better to have room in the bottom of the hole for a few reasons, the stress riser being the main reason, but also because if the stud bottoms out they can be a PITA to remove, sometimes needing to be EDM'd out . It's a lot better for the studs threads to bottom on the very 1st thread then to wedge itself into the bottom of the hole. The stud is a far superior alloy so the stress at the very 1st thread is not a problem.

I still want to know if you have ever installed a set of main studs? I tryd to answer your question, will you answer mine ?