sheared cylinder head bolt

[mdhbhouse]

Well I hate to admit but the great thing about forums in the anonymity it provides sometimes...

In my attempt to fix my older 96 cavalier with a blown head gasket I was able to take it all apart and if not for my stupid "it's gotta click mentality" on the torque wrench I ended up shearing off one of the head bolts when putting it back together. I should have known better but I wasn't sure how much torque 115 ft/lbs was and I was sure the wrench hadn't clicked so I just kept turning and hoping to god I was almost there!

Anyways an epic failure in my attempt to get the car running again.

To fix it what are my options?
1. Disassemble again and see if I can remove the bolt via some reverse drill bit?
2. Heli coil?

[j cAT]

Originally Posted by mdhbhouse

Well I hate to admit but the great thing about forums in the anonymity it provides sometimes...

In my attempt to fix my older 96 cavalier with a blown head gasket I was able to take it all apart and if not for my stupid "it's gotta click mentality" on the torque wrench I ended up shearing off one of the head bolts when putting it back together. I should have known better but I wasn't sure how much torque 115 ft/lbs was and I was sure the wrench hadn't clicked so I just kept turning and hoping to god I was almost there!

Anyways an epic failure in my attempt to get the car running again.

To fix it what are my options?
1. Disassemble again and see if I can remove the bolt via some reverse drill bit?
2. Heli coil?

I would use a reverse drill bit. do not disassemble. using the head hole as a guide. use a piece of tubing to keep the drill bit centered in the head bolt hole. using a slow speed and a drill smaller than the bolt dia drill out. the drill will catch the bolt and may unscrew it. since these do not bottom out you should be able to do this. let the drill do the work, do not use force to drill into the bolt. use a cutting oil.


with head bolts I would get new bolts. the bolts do get distorted with the heat and torque. then they become brittle.

the torque wrench needs to be calibrated, esp. if dropped.

[mdhbhouse]

First of all thanks for the reply. I find this site to be much better at people actually replying to posts compared to others...
So you are suggesting leave the cylinder head on and use a reverse drill bit to try and remove the bolt.
Not clear on the tubing point. You mean find some piece of tubing small enough in diameter to fit in the hole in the cylinder head, yet large enough to allow my drill bit in right? Copper tubing or what exactly would I be looking for?
Maybe the reverse drill bit docs will say or I can do some research but what is the size I would look for in relation to the bolt? 3/4's the size of the bolt to be extracted?

[DeltaP]

Sounds like you understand what j cAT's saying...at least thats how I read it and what I would do. Rigid copper pipe would be a good choice. Use the largest bit that fits inside the correct size tubing. Those are hardened bolts. Get a couple reverse drill bits as your gonna wear out some and alot of cutting oil. Keep that drill bit wet,cool and run it slow. Plug everything with rags, clean often and take your time. Good luck.

[Tech II]

Did you reuse the head bolts or get new ones?

Does the torque spec involve an angle? Torque to a spec and the final turn is an angle of so many degrees? If that is the case, it's automatic that the bolts be replaced....

[j cAT]

your reply is exactly what is required. the drill must be in the center of the broken stud . use of a piece of tubing of any metal copper is very good to ensure you bore into the center of the stud. using the drill to do the work ,,,, lightly work the bit to bore into the stud. using a slow speed with the torque limiter on not too high. as you cut into this stud I expect the stud to begin to unscrew.

If it does not un screw then you drill until you go threw the stud you will suddenly feel the bit drop . stop drilling then remove the head and using an easy out remove the stud.

I have used this method on bolts much larger on very large vehicles . to correct this type issue.

never use chinese bolts and or reuse bolts torqued to the max allowed . this is why I had to do this type of repair. the shop did not have new studs. reusing old studs under heat and stress is why this occured for me.

[mdhbhouse]

ok, 'j cAT' just a question about the actual screw extractor or reverse drill bit.
I really like the idea of working with the cylinder head not only as a guide but since it would save me a lot of work to not have to remove everything to get to the engine block.
I picked up a set of JET '5 pc spiral type screw extractors' which gives me an assortment but really maybe I need to just pick a couple of the correct size.
Regardless, they are not very long, perhaps 2 1/2" long so really not gonna work very well if I leave the head on.
So is the reverse drill bit different than an extractor or can I get them in different lengths?
IE. the head bolt is probably 5-6" long (don't have one in front of me now but approx).

For the record I did buy new bolts. It's just been a long time since I used a torque wrench and I guess I was thinking it would be a more 'audible click' when I hit the correct torque. Plus the others made a sound so I just assumed just a little bit more would do it...
The bolts were from the same place I bought the felmar gasket so I'm pretty sure NA made.

If I re-read your post it would appear the first step is to use a reverse drill bit and then the extractor to remove the bolt. Correct?

[j cAT]

Originally Posted by mdhbhouse

ok, 'j cAT' just a question about the actual screw extractor or reverse drill bit.
I really like the idea of working with the cylinder head not only as a guide but since it would save me a lot of work to not have to remove everything to get to the engine block.
I picked up a set of JET '5 pc spiral type screw extractors' which gives me an assortment but really maybe I need to just pick a couple of the correct size.
Regardless, they are not very long, perhaps 2 1/2" long so really not gonna work very well if I leave the head on.
So is the reverse drill bit different than an extractor or can I get them in different lengths?
IE. the head bolt is probably 5-6" long (don't have one in front of me now but approx).

For the record I did buy new bolts. It's just been a long time since I used a torque wrench and I guess I was thinking it would be a more 'audible click' when I hit the correct torque. Plus the others made a sound so I just assumed just a little bit more would do it...
The bolts were from the same place I bought the felmar gasket so I'm pretty sure NA made.

If I re-read your post it would appear the first step is to use a reverse drill bit and then the extractor to remove the bolt. Correct?

the reverse drill bit first. if the stud does not come out then you will have to remove the head and use the extractors. they are 3inches long usually. also to big on the torque ends to use in most cases in a deep bore.

use a small drill bit first. LET THE BIT DO THE WORK NO PRESSURE ON THE BIT.