Question about taps in repair stud kit

[Baltimore Sailor]

I've just received the repair stud kit OBLK_06_446, and I have a question about which tap is which. I've not used taps before, so the obvious is probably escaping me.

One of the taps is "normal" and the other "blunt", but to be honest, I'm not seeing the difference very well. I was expecting one to have a more pointed end and the other flat, but they both seem equally flat to me. Still, I think I've figured them out, but would appreciate hearing the word from someone who knows.

They are both labeled "7/16-14 H3", but one also has "HSS" written below that. They are also both labeled "Bosnia". (Which I figure is where they were made?)

Anyway, it appears that the "HSS" tap's cutting threads come a little bit closer to the flat end than the other tap's does. I guss that makes the "HSS" tap the "flat" tap, right?

At first I thought I'd received two of the same taps, but I was able to figure out that wasn't the case.

Sorry to be so dense, but in my old age I've lost my willingness to "wing it", especially in the face of drilling holes into my engine.

Thanks for all the help!

[Don Moyer]

It looks like you have your two taps sorted out correctly.

On another point, please be careful when using the 7/16" drill bit to set the stop ring carefully so that you don't drill down past the head. You'll be removing so little metal in this part of the process that you can actually grip the end of the 7/16" drill bit with a vise-grip and manually work the drill through the head - which is very convenient in limited space.

You can also use a vise-grip to work a 3/8" drill bit through what's left of the 3/8" threaded hole in the block to prepare it for the 7/16" "tapered" tap. In fact, as stated in the instructions (attached), by the time a standard stud pulls completely out of the block, you can usually use the 7/16" tap without even overdrilling the original 3/8" threaded hole.

Don

[Baltimore Sailor]

Again, thanks for all the great help and info. And now, yet another question, given as how I've never tapped new threads before.

How much force is required to work the 7/16" bit through the head, and then to cut the new threads? If I lubricate with 30W oil, will it be a slow but steady process, like putting a screw into a board with no predrilled hole? Or is it more of a back-and-forth process where you turn the tap a little, then back it off to clear the cutting blades, and then turn it a little more.

Is getting that drill bit started with vice grips going to be a big pain, or relatively easy?

In other words: I've never done this before, and what's the best strategy for doing it? When would I be concerned that the bit, or tap, is hung up and applying more pressure might snap something off in the head or block?

Oh, and one other thing -- I was surprised to see that that the hole for the stud passes through the block and into the water jacket. But there must not be much clearance there if you need the "flat" tap to get all the threads cut. Can you explain a bit about the construction of the head and block in that area?

Thanks very much yet again!

[Don Moyer]

How much force is required to work the 7/16" bit through the head, and then to cut the new threads? If I lubricate with 30W oil, will it be a slow but steady process, like putting a screw into a board with no predrilled hole? Or is it more of a back-and-forth process where you turn the tap a little, then back it off to clear the cutting blades, and then turn it a little more.

Not much force, and a back and forth process is best, as you suggest.

Is getting that drill bit started with vice grips going to be a big pain, or relatively easy?

The drill should start very easily.

In other words: I've never done this before, and what's the best strategy for doing it? When would I be concerned that the bit, or tap, is hung up and applying more pressure might snap something off in the head or block?

The force required to rethread these holes should not approach any concern of breaking the tap.

Oh, and one other thing -- I was surprised to see that that the hole for the stud passes through the block and into the water jacket. But there must not be much clearance there if you need the "flat" tap to get all the threads cut. Can you explain a bit about the construction of the head and block in that area?

I don’t have access to a cross-sectional drawing of the block that would show the spatial relationship of every head stud hole; however I can tell you from experience that most of the head stud holes in the block have straight, unencumbered access to the water jacket. Only 3 or 4 stud holes have cast iron blocking full access to the water jacket, but these obstructions are deep enough to still allow ample depth to install a repair stud. If you encounter a restriction along one side of the hole that would try to push the tap off to an angle, simply switch to the bottoming tap (the blunt one) and you’ll be able to get plenty of depth. I didn’t do a good job of keeping detailed notes on all the times I re-tapped a head stud hole, but if memory serves, these holes with a restriction along one side at depth were along the back of the block next to the coil.

Don

[Baltimore Sailor]

A few notes from my repair stud efforts today:

I had to go to Home Depot and get another 7/16" bit with flat faces on the shaft, as the round shaft of the one in the kit kept slipping in the jaws of my vice grips -- and I had that thing cranked down as tightly as I could force the grips closed. Perhaps that type of shaft on the bit should be the standard, rather than a round shaft..

Once I had a bit that I could get a good hold on with the vice grips, I found that putting two grips on the shaft, making a T-handle, really made the job easier.

Use LOTS of oil on the bit.

Now, a question about using the tap, since I ran out of time before I could do that part.

I tested the 7/16" hole with the repair stud, and it easily slid into the hole. Measuring its depth into the hole matched the top of the block perfectly, so yay for that.

How can I be sure that I have all of the old stud out of the hole? I used a 3/8" bit to clear the bottom, but it occurred to me that if a bit of the stud was still down there, how would I tell? How far into the hole should the 3/8" bit go? Looking at the difference between how far the repair stud goes into the hole and the 3/8" bit goes in, it looks like it matches the length of the coarse threads on the bottom of the repair stud. Does that sound good?

I'm puzzled that the tap does not slide easily into the same hole; it's going to need to be screwed down in there to get to the 3/8" part of the hole. Is that normal? I was expecting it to also slide right down to the place where the threads need to be cut.

Finally, how deep should the new threads be cut? I don't remember anything about that in the notes that came with the kit. Should I just tap until it bottoms out, or should I make some kind of measurement?

I feel like I'm getting close to the end here, but there's always another little frustration -- like today, when I had to remove the alternator bracket to have room to use the tap, and one of the studs came out of the block with the nut rather than just the nut coming off. Now I have another stud to reseat. (But at least it's not broken.) Since the nut pulled the stud out, I may just use the nut to screw it back in with some JB Weld on its threads and torque it down to 35 ft-lbs. Otherwise I can't see how to put that back in, since there's not enough thread above the head to double-nut it. [sheesh]

Thanks again for all your help.

[Don Moyer]

Steve,

Thank you! Your questions are causing me to focus way more than I normally do on this very important process, all of which is making this thread very valuable. I hope anyone who might be needing to use a 7/16" repair stud in the future has a chance to review your work before they start.

1) I've noted with interest your difficulty in holding on to our 7/16" drill bit with a pair of vise grips and will pass the information on to our shop technicians. There might be a good opportunity here for us to improve our kit - like by flattening the shank of the drill bit.

2) If you let me know which stud you're working on, I can be more specific regarding what you can expect in terms of the construction of the block below the stud hole. Meanwhile, here are some general observations:

a. Practically all stud holes develop a very hard calcified false bottom starting from the original bottom of the stud (usually 3/8" to 1/2"). This hard bottom will sometimes need to be drilled through with the 3/8" drill bit and gives some folks the impression that they are drilling through a piece of broken off stud. In 17 years, I've never found a small piece of broken off stud in a stud hole. The obstruction has always been this hard, calcified material.

NOTE: My calling this substance "calcified" may not stand up to the level of scientific scrutiny being displayed elsewhere in our Forum relative to the composition of sea water as it effects the corrosive process in blocks. I only know that the substance that develops below the original depth of studs is extremely hard in most cases.

b. I think your using the 7/16" repair stud as a depth gauge is a good idea to ascertain that you've cleared the hole in the head to the proper depth. The hole in the head being enlarged to 7/16" to the level you're describing should give you a good feel later when you begin using the 7/16" tap. Remember that the head gasket is approximately 1/16" thick and will usually intrude slightly inside the ID of the hole in the head. I don't recommend tempting fate by adjusting the stop on your drill bit to remove this thin layer of gasket. The 7/16" tap should go through the head gasket easily as it starts to cut into the material of the block.

c. When slipping the 7/16" tap through the new 7/16" hole in the head which you created manually (instead of using an electric drill), it's probably just a bit of a snugger fit than you were expecting. With the stop ring firmly installed at the correct depth, you could grip the drill bit again and wobble it around a bit as you turn it until the tap drops in more freely. Dry fit the tap frequently so as not to overdo this step.

d. If you look closely at the top of the 7/16" coarse threads of the repair stud, you'll notice a very important feature. i.e., the top of the thread stops at an almost imperceptibly small distance just prior to cutting all the way through the top of the 7/16" section. This tiny unthreaded area is intended to act as a stop when seating the stud "blindly" through the hole in the head and prevent you from seating it below the top of the block. In a through-the-head installation, this tiny unthreaded area of the stud will first encounter whatever is left of the head gasket so you will probably have to turn the stud approximately one revolution after it appears to be well seated.

As to your last question, do not under any circumstances torque a stud back into the block using the stud as you would a bolt (the stuck nut being the head of a bolt). This practice puts much more stress on the threads in the block and (almost as importantly) you won't get the proper "pull down" on the stud in the torquing process. The torque specification is based on the fine threads on the top of the stud. You should do whatever is necessary to remove the stuck nut(s), clean the threads well so that the nut(s) can be installed easily with your fingers after the stud is seated. Seating a stud through the head is a bit tricky since you have to grip the top threads. I always take a piece of cardboard and fold it over the top of the stud and use a pair of pliers to snug the stud down. You do not have to apply much force when seating a stud in the block, so the hardened metal of the stud will usually tolerate this process without damaging the fine threads. Your idea to use JB Weld on the coarse threads is a good one.

Don

[Baltimore Sailor]

Don -- thanks again for all your help and valuable info. (BTW, this is Jamie, not Steve, but that's OK -- the screen names don't help much in keeping us straight. )

The stud I'm replacing is circled below:



I'd mount the 3/8" bit in the vice grips and see if I could clear out any more of the hole if I could be sure I was working on the calcified plug and not drilling on the bottom of the water jacket. Would a better test be to put a screwdriver down the hole and tap it a few times with a hammer and see if it breaks through? Could I damage the water jacket doing this, or is it pretty thick at that point?

The repair stud slips very easily into the drilled-out hole; it actually falls into place when I release it. Should I continue enlarging it just a little by wobbling the bit as I manually turn it? Should the tap slide in just as easily as the repair stud? It probably does only need a bit more enlargement to slide in, but I want to be sure I'm not overdoing things.

That's a good tip about using cardboard to cushion the fine threads while using the grips to tighten down the stud. Do you think a piece of electrical tape wound on the threads, or maybe wrapped around the jaws of the grip, might provide as much protection and even better holding power?

I really appreciate the time you're spending with me on this subject. I agree that this would be a good thread to archive, as we've pretty much stepped though every aspect of the repair stud process.

Thanks yet again for everything.

[Don Moyer]

Jamie/Steve,

All your suggestions are good; tapping and turning a small screwdriver works well to clean out calcified deposits, the hole in the head probably just requires a bit more wobbling for the tap to fall in, and electrical tape should work to protect the top threads.

Don

[Baltimore Sailor]

I noticed that the 7/16" bit is listed as an 11.11 mm size. What do you think of drilling the stud hole out to 12mm rather than 7/16"? That would be the equivalent of drilling it out to just a couple thousandths than 15/32, and would eliminate the inaccuracy of "wobbling" the bit. Would that be too large for the purposes of the repair? I'd bet the tap would easily slide down in that size hole.

Also, did you have any information about possible blockage under the stud that I marked?

And finally , should cutting the threads be a constant, steady pressure, or a back-and-forth cutting motion like using the drill bit manually? And when taking out the normal tap to use the "flat" tap, is there much danger of missing the new threads and ruining them, or does the tap "find" the new-cut threads pretty well?

Thanks again!

[Don Moyer]

Sorry, I forgot that part of your question. The middle stud hole, second from the rear of the block has a straight shot at the water jacket.

When using a tap, it's best to use a back and forth rotation, advancing the tap slowly in the clockwise direction.

I never tried a 12mm drill bit, but then again I never had any trouble using a 7/16" drill bit. Why don't you try a 12mm and report back to us?

Don

[Baltimore Sailor]

I'll give the 12 mm a try on Wednesday when I get over to the boat.

Regarding the tapping part (upon which I am fixating obsessively), how far down do I tap? Do I just tap threads until it bottoms out, or should I mark it with tape? I'm guessing oil will help those cutting teeth as well, correct?

I've never ever tapped threads, and considering the importance of getting these right, I've got the nervous sweats thinking about it. I always like to visualize how things should go, so here's the scenario I'm picturing:

I drill out a little more of the hole so that the tap slides down easily until it hits the 3/8" part.

I oil up the "normal" tap, and begin turning it to cut the new threads. A little bit clockwise, then back off; a little more clockwise, then back off.

[Do I ever need to back the tap all the way out to clear the cutting blade?]

Cut until it bottoms out (?), then remove and put the "flat" tap in and cut until it bottoms out as well (?)

Insert and tighten repair stud with coarse threads coated with JB Weld. Sing Hallelujah!, wipe sweat from brow and crack cold one. Job done.

Sound about right?

[Don Moyer]

Sounds about right!

In the hole you're working on, there should be no restrictions below the hole so you can tap an inch or so and then dry fit the stud. The stud is long enough to "double-nut" the top of the stud to help you seat it into the block. If the stud goes in hard, try a bit of the wobble technique.

Don

[Baltimore Sailor]

Here's the followup from today's bout with the repair stud and taps:

I couldn't find a 12mm drill bit at Home Depot (nor did I see any metrics drill bits at all), but I did find a 15/32" bit, which is an 11.89mm bit compared to the 7/16" 11.11mm size. Surely that would be an easier drill-out, right?

Well, I don't know what the problem was, but the 15/32" bit wouldn't even touch the metal of the stud hole. The bit wasn't the exact same brand as my 7/16" bit, but it did say "metal". It may as well have been made of Slim Jim for all the effect it had trying to cut into the head. I ended up using the original 7/16" bit and "wobbling" it as Don suggested.

After a few wobbling passages through the head with that bit, the tap would slide about 1/2" down into the stud hole and no more. I figured that the whole damb raison d'etre of the tap was to cut threads into metal, and so if it slightly cut into the stud hole on the way down to where it was really supposed to cut, it wouldn't hurt anything. And so that's what I did.

The tap easily screwed itself down the stud hole to the bottom where it just as easily cut the new coarse threads. When that tap bottomed out I put in the "flat" tap and bottomed it out as well. Afterwards I tested the repair stud in those threads and it screwed in easy as pie. (Mmmm, pie!)

And the rest of the exercise went easily: I mixed up the JB Weld and stuffed some down into the threads with a screwdriver marked with tape so I'd know the correct depth, and slathered the coarse threads of the repair stud with it as well. I double-nutted the repair stud and cranked it into the head until it bottomed out as described in the directions. I also put some JB Weld on the other stud I needed to reseat, and luckily the fact that it was the alternator bracket stud meant that it was slightly longer than the other studs, so I was able to double-nut it as well and get it firmly in place.

Tomorrow I plan on stopping by after work and remounting the alternator, torquing the nuts and then firing up the engine. If this doesn't solve the problem of water in the #4 cylinder -- which I never had before having this stud problem -- then I don't know what I'll do next. Run the engine all season on three cylinders, I guess.

Further details to follow.

[Baltimore Sailor]

Well, she's all done. Sunday past I went over to the boat for the obligatory oil changes, running the engine for a few minutes between each change to mix up the oil. The first time I started her she ran like a top -- just purred at about 600 rpm at idle. The second time I started her I choked it again, thinking it would be cold enough, but she ran rough until I put the choke back in -- I guess she stayed hot enough to not need it. And after that she ran rough at low idle, though great at high rpms and accelerated "explosively", as Don likes to say.

I was a bit worried still, wondering if I was still getting water in the #4 cylinder. But when I pulled the plugs after the oil changes were done to check the compression, I saw the problem. The plugs were carboned up -- probably due to the choking when she didn't need it, and maybe from not getting hot enough during the short times I ran the engine between oil changes.

But there was nary a drop of water on the #4 plug. It was just as dry and carbon-coated as all the others, and when I did the compression tests no water came shooting up out of the #4 cylinder.

There was much rejoicing!

The compression was good all-around: at least 90 on all cylinders. I sprayed a little MMO on the valves when I put the plugs back in; maybe that'll clean the valves off a bit and help a little. When I go over on Wednesday I'm going to put in a new set of Autolite 437s, and then powerwash the deck and cockpit so she'll be ready for the Memorial Day weekend and the rest of the summer.

I offer a big shoutout of thanks to Moyer Marine, Don and who I believe was his lovely wife, who told me over the phone what distributor I had when I couldn't figure it out.

Also a hearty thanks to everyone on these forums who offered up nuggets of wisdom. I coudn't have done this head gasket replacement -- and all the little myriad other tasks that popped up in its wake -- without yinz help.

Fair winds!

[Don Moyer]

Congratulations! Now please enjoy your well-deserved season - and the next, and the next, etc, etc.

Don