Z-Bar Pivot Ball Threads Ruined

[Mark H.]

pivot ball threads.jpg
The last piece I was going to install before putting the engine back in the car was the engine side pivot ball stud for the clutch Z-bar. The threads had some previous issues and I tried to use a thread chaser to clean them up because the ball would not seat properly. The thread chaser sheered off in the hole. Never seen anything like it. Tried everything to get it out to no avail. Reverse thread drilling yielded what you see here. I see three options to fix.

Option one. Buy one of these brackets and see if it fits (I've asked the manufacturer the question but I'll probably just buy it so I don't lose any more time than I have to). https://sdparts.com/i-24074895-sdpc-...RoCyQ0QAvD_BwE

Option two. Helicoil. I have to admit I'm nervous trying to drill a hole that big (33/64ths) but it should be doable.

Option three. Take it back to the machine shop and see what they can do.

I'd welcome any comments on these options or any others I haven't thought of. Thanks!

Mark

[Gary R.]

Re: Z-Bar Pivot Ball Threads Ruined

What is the original size of the ball threads? Did you get the chase tool out, I can't tell from looking at the picture, it appears to be in there. I have good luck with the splined removers. The spiral ones you find in parts stores are no good.

I just had to repair threads in a 63 differential, the front bracket hole. Those are 7/16-14 threads and I used an insert over heli coil and it worked great.

[Mark H.]

Re: Z-Bar Pivot Ball Threads Ruined

The threads are 1/2-13. I’ve gotten pieces of the thread chaser out, but mostly I have just drilled the middle of it out. I used reverse thread bits, reverse thread tapered bolt removers and the like. It would not budge. I think I would be able to drill the hole for a heilicoil. 1/2 inch - 13 inserts use a 33/64 bit. If there was any residual material in the original threads after drilling, I don’t think it would be going anywhere. My biggest worry is getting the hole straight.

[Gary R.]

Re: Z-Bar Pivot Ball Threads Ruined

Well I guess I would try to get the chaser out and see what the hole looks like, it appears to be opened up pretty good. The iron is soft to drill but it may be possible to get a straight hole by hand by going slow. The insert I used required a .531 drill so you have to look at the wall thickness.

That bracket in your link is interesting, I didn't see those before. You may end up using it.

Good luck, keep us posted on what you end up doing

[Mark E.]

Re: Z-Bar Pivot Ball Threads Ruined

I agree with Dave. The bracket looks like a slick, safe and affordable option. The hole looks well hogged out, and if drilled or worked some more there's a risk you may "break on through to the other side" or weaken the block. Others may know how much material surrounds the hole, proximity to a water jacket, etc.

[Mark H.]

Re: Z-Bar Pivot Ball Threads Ruined

I have ordered the bracket. My only concern with it is that it will move the pivot ball too close to the frame, but we will see. Anyone know of a "stubby" pivot ball?

[Leif A.]

Re: Z-Bar Pivot Ball Threads Ruined

I have ordered the bracket. My only concern with it is that it will move the pivot ball too close to the frame, but we will see. Anyone know of a "stubby" pivot ball?

Mark,
Compare the two pictures below. One is of the bracket that you ordered with pivot ball. The second picture is a stock pivot ball. The one on the bracket appears to be considerably shorter than the stock one. I think they have already taken into consideration the length. If, in fact, they have used the stock type pivot ball and the bracket "hugs" the block closely, you should still not have an issue with the z-bar fitting correctly as there is a bit of room between the block pivot ball and the engine. You've probably found and elegant solution to your problem.

[Mark H.]

Re: Z-Bar Pivot Ball Threads Ruined

Thanks Leif - I hope that is the case!! If it is, I've got a new pivot ball free for someone . . .

[Dan B.]

Re: Z-Bar Pivot Ball Threads Ruined

Since you still have the block out of the car presently, I'd fix it properly or take it some place to be done for you. A good machine shop could remove that piece, weld it up, drill and re tap it and you won't have to worry about it going forward. Now is the time. Once you drop the motor in the job becomes much tougher if not impossible. More work, but worth it IMO.

[David M.]

Re: Z-Bar Pivot Ball Threads Ruined

Agreed with Dan. Fix it now. Impossible to do correctly in the car.
That is pretty ugly. No tool the same size thread as the ball threads will fix that. Has to be over sized.
You will make more of a mess. STOP...

No welding either. Not on an engine block with water jackets.

A competent machine shop can over bore and install a steel thread insert(similar to a heli-coil but not) or a threaded plug which can be center bored and bottom tapped...same idea as a thread insert. The machinist can advise which is correct for this application.
Some 271 or 518 red Loctite on the OD of the plug or insert and its permanently fixed.

The block needs to be fixtured so the drill can be centered to not "walk around". You get one chance at this.

Look up ReCoil Keyserts et al.

Exmple:

https://www.wdscomponents.com/en-us/thread-insert-thread-repair-303-stainless-steel-thin-wall-unc-inch-wds-830/c-428/p-34689

[Joe L.]

Re: Z-Bar Pivot Ball Threads Ruined

Agreed with Dan. Fix it now. Impossible to do correctly in the car.
That is pretty ugly. No tool the same size thread as the ball threads will fix that. Has to be over sized.
You will make more of a mess. STOP...

No welding either. Not on an engine block with water jackets.

A competent machine shop can over bore and install a steel thread insert(similar to a heli-coil but not) or a threaded plug which can be center bored and bottom tapped...same idea as a thread insert. The machinist can advise which is correct for this application.
Some 271 or 518 red Loctite on the OD of the plug or insert and its permanently fixed.

The block needs to be fixtured so the drill can be centered to not "walk around". You get one chance at this.

Look up ReCoil Keyserts et al.

Exmple:
https://www.wdscomponents.com/en-us/.../c-428/p-34689

Dave------


I agree; this is the only way to repair this correctly. The orifice in the block is too oversized and distorted for any kind of simple thread insert repair even if the tool fragment could be removed. If, for any reason, this cannot be done, then I think the best plan is to use the add-on bracket and leave the block repair for some future time.

[Mark H.]

Re: Z-Bar Pivot Ball Threads Ruined

Well, the bracket arrived today. Easy to install. The end of the ball stud wound up about 3/4 of an inch further away from the block than it would have been had I been able to install it in the block directly:

bracket 1.jpg

bracket2.jpg

bracket3.jpg

I think it will be OK, thought - I test fit the z-bar and had no trouble lining things up:

zbar1.jpg

zbar2.jpg

As someone said, an elegant solution to the problem. I think the engine goes back in the car tomorrow!

Thanks to all for their help getting me to this point.

Mark

[Gary R.]

Re: Z-Bar Pivot Ball Threads Ruined

That works. I would have been figuring a way to get it in my mill and centering it and repairing it. Your bracket works and saves a lot of time and aggravation.