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Sheared bolt harmonic balancer

Jonk67

Jonk67

Well-Known Member
Well the good news is I think this is the first bolt I've sheared from teardown to rebuild, even the exh. bolts and front leaf spring bolt came out with just some spray and torque. I'm glad this car was used it whole life instead of sitting.

Of course it happened after midnight when i had gained super strength from drininking beer all day working on the car. I checked the shop manual and the only spec I could find (that I could focus my eyes on) for the crank pulley bolts was ' Damper or pulley to crankshaft - 70-90ft/lbs. Well that seems like a lot of torque now for a 3/8" bolt but 2/3 clicked at 75ft/lbs. but not the 3rd....I can't find any torque specs for the crank pulley 3 bolts, any one know?

IMG_1408.jpg


Now, do I do some careful centered drilling and pick up an easyout from my local Fastenal and give it a go on this new balancer or take it to a local shop and pay $X to have a pro do it, be done and continue installing parts? As you can see the hole goes all the way through so i think that makes it a little easier, wonder if I could soak it and start a bolt from the other side to help? There's nothing sticking up to grab and I don't know how clean of a slot I could cut into it with a dremel to try a flat blade screwdriver.
Jon
 
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if you think you're gonna have trouble, bring it to me & i can fix it up. worse case, i can center drill & chase it out with a tap afterwards...

p.s. you need to start drinking that black label crown royal like i do. it mellows you out instead of giving you a case of the red a$$ that makes you start breaking stuff like beer does :beer
 
I'm pretty sure the Dampner to crank torque is 85-100 ft-lbs and the pulley to dampner torque is 35-50 ft-lbs
 
If you snapped the bolt off with a wrench I doubt very much cutting a slot for using a screwdriver is going to yield you successful result. I see drilling in your future.
 
I would set it up for drilling it on a drillpress, then use an ez out to remove it.

On the other side of that coin, it may just back out by turning it.
The bolt broke off inbetween the pulley and dampner, so it may be loose enough to spin free.
 
Thanks guys, I'm hoping it's going to come out easy, both threads were clean. I think I found the reason it snapped, I flipped the balancer over to look at the back of the thread and the wt. is covering that hole. I think the screw bottomed out on the wt. and snapped since it couldn't advance. I'll try removing the wt. tonight as it's 2 hex bolts and I just looked at it this morning. Hopefully once the wts. off the screw will turn easily with some lube.

Thanks for the offer as usual Steve, I want to get out to see the progress on the shop anyway so if I can't get it to move easily I think the drill press is the way to go. Let me know if you come across the trans support you made for me, I have it supported with a furniture dolley but it dropped off once when I tried to roll the car out.
I thought about switching drinks but hard liquor had some ugly :barf1 (and fat) consequences normally when I was single and drank the hard stuff....I may have to give it a second try now that I'm married :wth
Besides, Beuning keeps reminding me of the sober children in India, I can't have that on my conscience.

I'll try 50ft/lbs. with the new bolts when I get it out.
Jon
 
grind the top a little flatter
center punch it
Take a very small drill bit and drill it step by step bigger.
A small drill can hold the center better.
At some point , you can use a torx bit , drive it into the whole so the tooth of the bit, bites into the metal and try to loosen the rest of the bolt.

yeh yeh bad explenation. :rant :rant
 
The last time I busted off a bolt, a friend suggested when drilling it out to use a reverse rotation drill bit.

Here was his reasoning: Most normal drill bits are fluted and sharpened to turn in a clockwise direction. When you drill into the broken stud it's actually tightening the stud in the hole, unless the other side of the hole is open and it was threaded all the way through. That only serves to make it worse. The reverse or left handed drill bit is fluted and sharpened the opposite direction for rotation in a counter-clockwise direction. When you are drilling the stud out with one - use a bit slightly smaller than the normal tap size for that hole. As you drill you are hollowing out the stud, at some point it tends to grab the stuck stud, then the fact it's turning counter-clockwise it'll turn the stud right on out for you.

I can't say if there's any truth behind that since I don't own any reverse rotation drill bits, but logically it does make sense.
 
"66gt350" said:
The last time I busted off a bolt, a friend suggested when drilling it out to use a reverse rotation drill bit.

I can't say if there's any truth behind that since I don't own any reverse rotation drill bits, but logically it does make sense.
Click to expand...

If I had access to it , I surely would take such drill bits. !!
 
Pulley to damper spec is

25 to 35 for UBS bolts

35 to 45 for Place bolts. What you were using.

You used the damper to crankshaft spec. (lol) lucky you did not break them all.
 
Well just as I had hoped, once I got the wt. off (had to find a 6MM hex in my collection) the head of the bolt was exposed. Was able to turn it with a set of needle nose and unscrewed it. Not sure where to get Pace bolts, might have to come up with an order of misc. stuff to get them in AMK from one of the mustang houses. Would it be acceptable or 'wise' to use G8? and go 35-45ft.lbs.

Wow those orignal bolts torqued past double what they should have been without shearing until I bottomed the one. Now I know the depth for that one but I'll get them all that length so they match in case I ever take them out again and mix them up.

Thanks all,
Jon
 
I'd toss the remaining 3 in the trash and just go with some Grade 8 bolts, unless they are some special length that I'm not aware of.
 
Yeah, I was going to put the 2 that I overtorqued to 75ft/lbs in the spare bolt bucket and get all 3 new grade 8 the length that the 1 bolt snapped at so in case I ever remove the pulley again I won't mix up one short bolt.
Jon
 
Personally, I'd just toss the other two bolts. If you over torqued them, you might have stretched the bolts enough to weaken 'em.
 
Were those AMK replacement bolts? I've had terrible luck with those also. Sheared off on 3 different cars. One of the very few total crap fasteners that they sell.
 
"caspian65" said:
Were those AMK replacement bolts? I've had terrible luck with those also. Sheared off on 3 different cars. One of the very few total crap fasteners that they sell.
Click to expand...

No they were the original bolts, Sluggo calls them Place bolts?

I won't get the AMK's then, just picked up some grade 8 3/4" long ones that look like they'll be the perfect length.
Jon
 
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