Head Bolt Snapped Off In Block...

[84seven20]

Hi all,

 

I bought this truck as a project a while ago and have been very slowly working on repairing it. I had noticed white smoke from my tailpipe and figured the head gasket was probably bad as is common with these trucks. I thought I would start by re-torquing the head bolts and see if that fixed the issue, then replace the head gasket if it didn't. Well, the worst happened: one of the head bolts snapped off when I was trying to re-torque that bolt after removing and cleaning it... and it snapped off at the top of the threads.

 

I guess I must have torqued it way too tight but I swear I didn't hear a click from my torque wrench (pittsburgh 3/8 drive w/ a 2" straight extension). This was the third bolt I was working on, first two were fine/no issues. 

 

Any thoughts on how to get this SOB out of there? I'm thinking I'll very carefully try to drill the bolt out (using something like this) and use a set of screw extractors. I'd certainly appreciate any guidance and thoughts on how to do this, feeling pretty defeated...

[84seven20]

[datzenmike]

I think taking the head off to do this is the best bet. Center punch the top of the bolt so the hole goes down the center. Start with a 1/8" then a 1/4" hole if you can go down straight. The bolt is 14mm or just short of 3/8. Then an easy out. 

 

If you go this route you know to block the timing chain tensioner from falling out before removing the cam sprocket?????? right???

[thisismatt]

Weld a nut to it, remove easy peasy

[datzenmike]

Depends if the nut reaches the top of the broken bolt.

 

Maximum tightening torque is between 100 ft lbs (for an M12) and 150 ft lbs (for an M16) there was no M14. Maximum torque is 70% of the yield point so add 30% and this, is where the bolt starts to to stretch beyond recovery. Even if removed the bolt is ruined. If tightened over 100 ft lbs then it can be presumed that the easy out will need to exert this amount to back the remains of the bolt out????

 

 

[84seven20]

14 hours ago, datzenmike said:

I think taking the head off to do this is the best bet. Center punch the top of the bolt so the hole goes down the center. Start with a 1/8" then a 1/4" hole if you can go down straight. The bolt is 14mm or just short of 3/8. Then an easy out. 

 

If you go this route you know to block the timing chain tensioner from falling out before removing the cam sprocket?????? right???

 

Ok, great! I was thinking that getting the ends of this bolt out would be near impossible but if I can get the head off then it should be much easier for me to reach it. Still going to suck but at least not quite as much!

 

I've read a few 720 head gasket repair threads and bought this tool when I got the gasket repair kit. I believe it should help keep the chain tensioner from falling it as well as keep the chain from falling into the cover. Do I just loop the string part onto something so the wedge doesn't move/fall into the chain cover?

 

 

[Stoffregen Motorsports]

Careful welding a nut. If you do this and the nut breaks off, and you try it again, eventually, the broken bolt becomes case hardened and cannot be easily drilled. This has happened to me a few times.

 

Also, be super careful that the drill bit or extractor do not break off. Getting bits and pieces of hardened steel out of a blind hole...You may as well get the cutting torch out.

[Dave 240Z]

15 hours ago, 84seven20 said:

trying to re-torque that bolt after removing and cleaning it

That would tell me the bolt shouldn’t be tight after snapping. That broken thread sticking out of the bolt shaft may be enough to grab the threaded part and back it out. If so, a magnet should pull it out from there.

Otherwise, there are left hand drill bits for easy out kits that might grab it and back it out. But maybe not long enough.

[Stoffregen Motorsports]

If there is any bolt sticking out at all, grind it flat before trying to drill it. This will give you  a nice flat space to center punch.

 

And maybe try a little heat and penetrating oil first. Heat it up, spray it down and then try to remove the bolt. If it doesn't come right away, let it cool completely and try again.

[84seven20]

3 minutes ago, Stoffregen Motorsports said:

Careful welding a nut. If you do this and the nut breaks off, and you try it again, eventually, the broken bolt becomes case hardened and cannot be easily drilled. This has happened to me a few times.

 

Also, be super careful that the drill bit or extractor do not break off. Getting bits and pieces of hardened steel out of a blind hole...You may as well get the cutting torch out.

 

I don't actually have a welder so I'm planning to go the center punch, drill, extract route. Good tips on the heat and penetrating oil, will definitely give that a go!

[Stoffregen Motorsports]

Good luck.

[Duncan]

I have a set of left hand drill bits.  I usually start with a very small size, go slow, and increase the size in small increments.  I've had much better success with that than I've had with easy-outs.

 

Good luck, either way.  

 

 

[thisismatt]

30 minutes ago, Stoffregen Motorsports said:

Careful welding a nut. If you do this and the nut breaks off, and you try it again, eventually, the broken bolt becomes case hardened and cannot be easily drilled. This has happened to me a few times.

 

Also, be super careful that the drill bit or extractor do not break off. Getting bits and pieces of hardened steel out of a blind hole...You may as well get the cutting torch out.

 

My 2¢ is that I'd rather weld to it than try to remove a broken easy out or drill bit.  Personally never broken an easy out/extractor, but I've broken taps and had to remove them and that is not fun...

[Stoffregen Motorsports]

20 minutes ago, Duncan said:

I have a set of left hand drill bits.  I usually start with a very small size, go slow, and increase the size in small increments.  I've had much better success with that than I've had with easy-outs.

 

Good luck, either way.  

 

 

Yes, start small and make 100% certain you are in the center of the hole. If the drill starts to drift to one side, correct it. Most times, a perfectly centered hole can leave just the threads of the broekn bolt, which can be scraped out with an awl.

16 minutes ago, thisismatt said:

 

My 2¢ is that I'd rather weld to it than try to remove a broken easy out or drill bit.  Personally never broken an easy out/extractor, but I've broken taps and had to remove them and that is not fun...

Right, but what I said above applies. The nuts sometimes break off and if you weld them too many times, good luck drilling it. Maybe drill it first and then try the welded nut.

[datzenmike]

 

The above is intended to be installed below the cam sprocket and hammered down wedging the chain and holding it. Obviously the engine must not be turned so slip into neutral. The rope is to pull the tool out when done. 

 

This is a better style and blocks the tensioner. Much better but hard to find..

 

[bottomwatcher]

5 hours ago, Dave 240Z said:

That would tell me the bolt shouldn’t be tight after snapping. That broken thread sticking out of the bolt shaft may be enough to grab the threaded part and back it out. If so, a magnet should pull it out from there.

Otherwise, there are left hand drill bits for easy out kits that might grab it and back it out. But maybe not long enough.

This! If the bolt was turning before it snapped there is a good chance it is finger tight. 

[Logical1]

3 hours ago, datzenmike said:

 

The above is intended to be installed below the cam sprocket and hammered down wedging the chain and holding it. Obviously the engine must not be turned so slip into neutral. The rope is to pull the tool out when done. 

 

This is a better style and blocks the tensioner. Much better but hard to find..

 

 

This is an L series wedge, am I wrong?

[Logical1]

This is one of mine I made of a wooden coat hanger for Z series engines, not sure what wood they use but it is hard as hell and they have always treated me perfectly. You can leave the nose a little longer also.

 

Edited March 26, 2022 by Logical1
Spelling

[datzenmike]

50 minutes ago, Logical1 said:

 

This is an L series wedge, am I wrong?

 

The Z and L chain guides are the same but for the lengths at the top. L tool will work.

 

 

 

 

This is mine. When pushed down all the way to the bottom the pointy end pushes the chain against the tensioner. It's kind of like a stiff spring.

[DuallyDatsun]

Another point, since you already had one bolt snap. Get all new head bolts. You don't know what sort of stress they've all been under, but if you had one bolt snap, it's not a bad bet to think other bolts might be in danger of snapping. Better safe than sorry here. Would hate to go through all that work only to have another bolt snap off when putting it back together.

[Stoffregen Motorsports]

Bolts can bottom out if the washer is not installed, and this can cause them to snap. Debris from cleaning the block surface (head gasket) can also partially fill in a hole and cause a bolt to bottom out.

[datzenmike]

On 3/25/2022 at 4:33 PM, 84seven20 said:

 

 

I guess I must have torqued it way too tight but I swear I didn't hear a click from my torque wrench (pittsburgh 3/8 drive w/ a 2" straight extension). This was the third bolt I was working on, first two were fine/no issues. 

 

 

 

Possibly operator error and missed the click. These are not torque to yield bolts that are designed to stretch and are thrown away after one use like the KA series. If this was stretched too far (you would have to look up what a 14mm metric grade 10.8 bolt's yield strength is. M12 is around 120 ft lbs and M16 is around 155 ft lbs) this was done previously and unlikely.

 

The bolt bottoming out from missing washer or debris would still have stopped at 60 ft lbs it's just that the head would not have been properly clamped.

[bilzbobaggins]

Possibly china fucking him in the ass.  I bought a pittsburgh torque wrench.  I returned it the same day.  No where near close.  Checked against two that had just been calibrated.

[720_Jeff]

I'll add in here.  Many many years ago.  Had an igniter module on a Honda Civic, ~1990, forget the exact year.  Had Factory Service Manual.  Bought a brand new MultiMeter from HomeClub.  That tells you how long ago, lol

Meter had a reading which indicated it was faulty.  Them tested new igniter and it had a very similar reading.  Took igniter to dealer, with MultiMeter, showed them readings, and they were very kind and allowed me to refund my igniter, seeing my old/new had same readings. 
As we all know, electronic parts are usually non-refundable.  I was so grateful, as at that time, that was 2-3 days wages, they allowed a refund 🙂 

 

So, knowing the accuracy of instruments is critical!

 

Edited March 29, 2022 by 720_Jeff

[Stoffregen Motorsports]

I have learned to never rely on cheap torque wrenches.