Engine Rebuild Crankshaft Questions

[DanT]

DL:B,

Yes, you got it. It is one of the bolts with the 14 mm heads... and the 10mm hole size. Agree, I would not want to overtorque those bolts... and I did not do that when I put them in myself last time. But the damage has been done... and I certainly want to fixt the problem correctly the first time.

I think the first thing to try is to run a tap in with the same size bolt threads. Then use a new bolt. Might work, and nothing to lose. Next step might be to try the same thing with a 10mm all thread and loctite anda a nut??? Again, not damage done to the hole size yet, and if it works it works.

Final step would be to enlarge the hole for 7/16 tap or helicoil.

RER: I was thinking abouty going with the 7/16 tap alreadly. VERY HELPFUL to know this actually worked. Certainly suggests that creating a stud like that and using a bolt is likely to work for me also (though the corrosion in my bolt hold might be a variable).

Do you think it would work just as well with a 7/16 bolt? (Putting he sway bar on and off in the future might be difficult with a stud in the front hole of the bracket. But if I knew this would work better with an "all thread stud" then it might be worth the inconvenience.

I will study this a bit more before doing anything. These suggestions have been extremely helpful. If anyone else can add 2 cents please do!

Thanks so much for chiming in.

Dan

[DanT]

IF it turns out that I need to tap this stripped bolt hole on the sway bar bracket, then the idea of using a 7/16 bolt is starting to become more appealing than the 10 mm heli-coil kit (cost is not a factor for helicoils at $30 to save a T4 front end).

That said, by coincidence I actually have the correct drill bit for the 7/16 tap ( set of machine bits from A to Z), and one of the 2 taps that I have is actually the 7/16-20 fine thread .

Here is what the comparison looks like:

- Current hole size at the outside of the threads :10mm
- W bit used for 7/16 - 20 (fine) = .386 inches = 9.8 mm.
- (Running this bit into the hole essentially takes out the threads only. No more.)
- 7/16 bolt = 11.1 mm, so a tap that cuts new threads will essentially cut .5 mm of thread on each side of the new hole... into new metal... essentially expanding the outside threaded part of the bolt hole from 10mm to 11.1 mm.
- I want to believe that there is at least .5mm of new metal on the each side of the current threads to work with.
- Is 7/16 course thread or fine thread better?


The helicoil inserts are actually 12.1 mm across OD (same as a 12 mm bolt OD, so the 10 mm helicoil tap is going to cut threads back to 12.1 mm instead of 11.1 mm for the 7/16 bolt.

Not sure how this plays in, but I do need to tap a hardened steel capture nut... which is a different application than what the the helicoils usually see in a block or head situation. Is it possible that a direct tap for a 7/16 bolt is a better choice going into hardened steel also?

Comments certainly appreciated...
Thanks.

Dan

[Jarf]

If it were my car, I would be installing a heli-coil with new bolts from the factory.

Ordering new bolts from the dealer will of course seem expensive but the part you don't see is that the bolts you buy at the local fastener store, even in the correct thread size will almost always have the large head (17mm head on a 10mm bolt, vs OE - 14mm head on a 10mm bolt).
Even if you find "small head" japanese threaded bolts, the plating on those bolts is not comparable to what the factory uses.
You will only find this out a year or 2 from now, when you try to remove it and find a ball of rust, seized in place, regardless of how much A/S is used.
As an added bonus, having the correct head size simplifies future servicing as one tool fits all the same bolts, instead of making a couple of trips back to the box to find the correct wrench/socket. In a lot of cases, the big-head bolts will fit just fine, until you get it almost tight and when the tool slips and rounds the points and creates further problems, aggravation and delays.

If you go with the 7/16in route, you may not have enough meat left in the nut for a heli-coil repair down the road, if you ever have to go there.

I realize that many people have successfully effected repairs in a variety of ways, but I am anal retentive, I like things to be "as they should" and most importantly, Murphy is a close relative. I also tend to keep my vehicle(s) forever, so the better the repair up front the least likely I am to regret it, down the road.

I have used heli-coils in a variety of applications, under all load types including brake calliper saddles and have NEVER had an issue with the repair.
I do, however, ALWAYS install my coils with RED (permanent) loctite (it just avoids having the coils back out, IF the bolt seizes in future)

I also use liberal amounts of Never(anti)-seize, and do not reduce torque specs, but do use a torque wrench.

If the nut stripped out while being torqued to spec, you should THANK your neighbour, because that nut was already compromised and it is better to find out in the driveway than during a panic stop at high speed.

[Jarf]

As to cutting thread in a hardened nut, same procedure, only go a little slower.
Take your time, don't rush and when it starts to bind, back off and clear the debris.
NEVER force the tap, bad things will happen. Removing a broken tap is a much bigger PITA than anyone can imagine.

I tend to use a quality penetrating oil (as it is thin, provides cooling and will clear cutting debris) liberally.
You may find you have to back the tap out all the way, several times during rethreading, sometimes the debris will prevent you from doing that.
That is why you want to go slow, small movements making sure all is clear and the tap turns smoothly.
A hardened nut will be harder to thread so just go a little slower, and be more vigilant about keeping the hole clear of debris.

The big trick is the aerosol lubricant, I am always amazed how much heat can build up during a rethreading procedure.
Cut in little bits, 1/8-1/4 turn at a time, then back it off, all the while keeping the debris out of the holes.
Sometimes going a 1/2 turn will result in a broken tap, if you see smoke, STOP and let it cool and use liberal amounts of lubricant.

[DanT]

The good news is that this awesome T4 is now back on the road!

Engine is running smoothly, and is not showing any signs of trouble. No leaks. No strange noices. This is a huge relief for me, and I am cautiously psyched about driving the car! (It is a nice looking car and I get a lot of comments on it where ever I go.) It is also very cool to know what is inside the block now as I chug up and down the steep hills in this heavily glaciated Finger Lakes Region.

THANKS TO ALL OF THOSE WHO HELPED COACH ME THROUGH THE TASK OF INSTALLING NEW MAIN BEARINGS AND ROD BEARINGS WITH THE ENGINE IN THE CAR. I would not have been able to figure that out on my own. Absolutely fabulous to have such high qualtiy help on this... and very much appreciated.

As for the stripped bolt on the front sway bar bracket: I decided to tap the hole for a 7/16 fine thread bolt (11.1 mm)... as that appeared to be the trick for not going into any more metal than was needed to get the job done. This worked out fine. My biggest concern was that I did not know how much metal was available on the sidewalls of the captured nut. (I have broken off a captured nut in a frame before and have no desire to ever be in that position again.) The head of this new bolt is 5/8, which is very close to 16mm, and for me it works fine and looks fine in the current location.

In hindsight, I think there was enough metal in there to tap threads 1 mm larger to get to the 12.1 mm needed for a helicoil... that would then take the original bolt with the 10 mm thread size. That said, I knew the 7/16 route had been completed successfully before... at least with a course threaded rod... and that was very helpful to know going into this. Tapping the hole by hand was not difficult. If I had to do it again, I could be convinced to go either way.

THANKS TO ALL THOSE WHO HELPED WITH THE STRIPPED THREAD PROBLEM. This was new territory for me, with a lot on the line. Very much appreciate all of the help from everyone!

Checked my records to see that I have now had this car for 16 years, and have taken the odometer from 173k to 242k... with the car up on blocks for 5 years of that span. Lower part of the engine is one of the few locations I had not opened up yet. My approach has been to fix things when they break, but since the engine was not broken ... until now... I just never had gone in there. (Had a yellow 83 T4 deluxe wagon for 11 years prior to buying this one. I did not know how to seal that car against the rust, and the salt took out the body on my first T4.)

The current yellow 83 T4 has about 1/4 inch of leak stopper roof patching compound, combined with roofing fabric, along the entire bottom and up into the wheel wells. Essentially it has a commercial tar roof for the bottom of the car... leaving no exposed sheet metal... and no exposed sheet metal edges inside the fenders. I get the Leak Stopper at Lowes. It has a high rubber content and is far superior to any undercoating I have ever seen... when troweled on with no exposed edges.

I also use Chassis Saver directly on any exposed metal underneath... drive shafts, axles, differential, etc, and as a primer for any finished top-coated surfaces above. Chassis Saver is the only product I have ever found that will go directly onto rusty metal and stop it dead. I have found this product to be superior to POR 15. Prep is minimal. (It is used on the frames of the salt trucks in PA) With patience it is possible to use chassis saver to do body repairs on the main body of the car also...and to use a thin body glaze over to the top of the Chassis Saver... and to sand and topcoat it for a completely invisible repair.

For those living in the rust zone with T4s hoping this might be of some help...

My best regards.

Dan

[ARCHINSTL]

Congratulations on your odyssey!
Thanks for the underbody tips as well.
And - you are correct in remarking about the help available here; there are many talented people who give freely. This is heartening, with very little drama or no sniping evident.
Tom M.

[keith]

I wish I had followed this topic a little closer, especially when it got off track about the stripped threads. Too late for Dan, but just a bit of info here, there are two types of taps, thread cutting taps and roll forming taps. Roll forming taps are used in Europe more than in the US and they form a more durable thread, but they are harder to use. In the US they are sometimes called thread restoring taps.

I like these because they will in many cases, they will actually restore a thread to like new condition. The really nice thing is that you can borrow a set (big deposit though) from O'Rielly's autoparts. A thread restorer is always my first choice in thread repair and so far, since discovering them, the only choice that I've needed.

BTW, if you use a roll forming tap to make new threads, the hole size is much larger than the hole for a thread cutting tap. If you drilled the hole size for a roll forming tap and then tried to use a thread cutting tap, you would only scratch the surface of the hole.