Hard telling, sometimes metal just has flaws. The only thing that catches my eye is the broken threaded part that you circled. Is that how you found it or have you backed it out part way? As shown, it doesn't look like the stud was tightened all the way to the shoulder.
Broken engine side z bar pivot
Thanks in advance for any replies.
I broke my engine side z bar pivot this week out of the blue while driving. I don’t see any posts about this other than the person that broke one due to a bad engine mount. That doesn’t seem to be my issue. Anyone have any idea why my z bar pivot would break? Old age? Fatigue? Currently waiting on the replacement to arrive. Nothing else seems damaged. I easily removed the broken stud.
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I broke my engine side z bar pivot this week out of the blue while driving. I don’t see any posts about this other than the person that broke one due to a bad engine mount. That doesn’t seem to be my issue. Anyone have any idea why my z bar pivot would break? Old age? Fatigue? Currently waiting on the replacement to arrive. Nothing else seems damaged. I easily removed the broken stud.
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Yes - that might have been the issue. I backed it out a little with my fingers before the photo. We probably didn’t put lock tight on it before install.
Maybe clutch has too much pedal pressure.
my guess it was loose in the block, for sure the shoulder should be up tight to the block.
Hard to tell in pics, the metal may have been fatigued. Take a pic of the end surfaces where they broke. It may have had a small crack that eventually snapped. A way to tell is on a fresh break the metal will be kind of a shiny crystalized lighter grey, then there will be a section that is dark grey or blackish. metal will oxidize when exposed to the air and turn dark.
Shiat happens...why?
50+ year old part finally said stop.
was not threaded in all the way.
was an aftermarket low grade quality.
Been a defective part for 50+ years and finally let go.
clutch has been repeatedly over extended adding greater force to outboard parts.
B&B 3 finger clutch.
50+ year old part finally said stop.
was not threaded in all the way.
was an aftermarket low grade quality.
Been a defective part for 50+ years and finally let go.
clutch has been repeatedly over extended adding greater force to outboard parts.
B&B 3 finger clutch.
Yep...loose....Yes - that might have been the issue. I backed it out a little with my fingers before the photo. We probably didn’t put lock tight on it before install.
Thanks all. New part arrived today and is going on with threadlocker.
You can always go hydraulic and eliminate that part and others. Get more room down there. I think I can R&R my header without lifting the motor now.
I broke a few back in the day when I ran a heavy Borg & Beck/Long style clutch with heavy pedal pressure. I replace it with a Centerforce and never had another issue.
Yeah those 3 finger B&B clutches took a heavy leg to depress pedal and no doubt stressed Z bar components, fork. Diaphragm clutch type WAY easier on all.
This is more common than you think. Never thought this could happen Personally, I wouldn't use locktite in case another ever snapped off, you'd have a hard time getting it out. Make sure you only use a GM one (# 3866568) and make sure there is no paint on the block where the pivot ball seats against it.Yes - that might have been the issue. I backed it out a little with my fingers before the photo. We probably didn’t put lock tight on it before install.
Only one I ever saw broken obviously had inclusions in the metal so was defective.
Could never understand why they never spot faced that surface. Depending on the block casting, sometimes the face of the pivot and the block aren’t parallel, causing a stress point.
Good point. It would be easy enough to have it machined when its at the engine builder.Could never understand why they never spot faced that surface. Depending on the block casting, sometimes the face of the pivot and the block aren’t parallel, causing a stress point.
I may have more than one NOS one in stock. Might be able to still get those at the dealer.
Agree with Animate me reply #2. Stud has no signs of ever the ball base flat ever being firmly seated on the block, so years of use and high operating forces would eventually lead to this. Notice all the grease around the broken stud on the block and under the ball base flat, had those surfaces been in contact they would be clean, the flat never was in contact with block. Further proof is the orange paint on the unmachined surface of block shows no signs of hardware ever being tightened against the painted surface, you would expect to see some paint missing at least on the high points of the casting. I would also make sure the broken piece removed from block doesn't show signs of the stud bottoming out if this isn't a through hole. I have drilled and tapped 400 sbc pads to accept a z-bar stud but don't recall if it was a blind hole or through hole. But just make sure your new one will fully seat against the block. If it is not a through hole and bottoms out I would be inclined to grind the stud shorter and NOT try to drill & tap the block deeper.
Also thanks for posting this. I now have one more thing to verify on my 68 sb. I didn't install the Z-bar and it squeaks, lube hasn't helped and it isn't the bushings in the pedals or rod from the pedal.
Also thanks for posting this. I now have one more thing to verify on my 68 sb. I didn't install the Z-bar and it squeaks, lube hasn't helped and it isn't the bushings in the pedals or rod from the pedal.
I guess post #9 will solve the mystery.
Thanks for all the info and replies. Good info here on a problem I wasn’t sure many people had. I’m going to try to keep the car as original as possible, even though it is not matching numbers or even an original paint color. The few things we have done to modernize it (like modern ac) haven’t been as beneficial as I was thinking they would be for the cost.
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