Bottom tapping for ARP 625's

[blackstacks]

When people are referring to "Bottom Tapping" the holes are they meaning actually cutting new threads deeper all the way to the bottom of the hole, or just running a bottom tap to the bottom of the existing holes to clean them up? Ive heard both ways.

I was planning on cutting new threads in all the the holes all the way to the bottom for full thread engagement, but the studs will still not bottom out in the hole?
The shoulder of the the stud seams to be hitting the top of the hole, long before the tip of the stud hits bottom. Does this seam right?

Can you actually cut the threads too deep?

I tried to draw a pic to illustrate whats happening.

 

[Tate]

If the shank is hitting the top of the hole, bottom tapping does you no benefit. Main thing is getting the threads clean, make sure to back them out a bit before you start torquing. When I'm on the final pass, I back off each nut to re-lube and bottom the stud and back out a half turn as it will turn during the previous passes.

 

[WUnderwood]

You are over thinking it. You need clean threads, and tapping the hole will ensure that.

 

[blackstacks]

Thanks for the replies. I went ahead and bottom tapped all the holes and threaded all the way down and I did gain a couple threads on some some of them. Now all of them bottom out on the shoulder of the stud, not the tip.

Now with that being said, what confuses me is that ARP says to screw in the studs snug. What is snug? Snug with your fingers? Snug with a Allen socket and small ratchet? Then a lot of guys say not to bottom them out, but to back them out 1/4 or 1/2 turn.

Which is the best way to go?

 

[White Knight]

Bottom tapping for studs originated with A1 and the old style ARP studs for a 12 valve to get the stud to fit under the valve cover. With newer ARPS or engines you only need to clean out the threads and you're good to go.

Unless you drilled the hole deeper, no, you can't tap too deep. Like these guys said: clean the threads, screw in all the way and the back off 1/4 turn.

I always install them finger tight then back off a tiny bit. No problems yet.