Broke crankshaft gear bolt

[DevoBuzz]

So in putting on the timing gear on the crankshaft I snapped the bolt. About 3/4 inch is stuck inside the crankshaft on my brand new all forged shortblock. I assume this cant be fixed myself but can it be fixed at all? Will the crankshaft need to come out?

[supercrackerbox]

I assume the engine is still out of the car? I would honestly call some machine shops and see what they say. It would be easier in the long run.

[Vigo]

Well, it CAN be removed. There are several methods and no telling which one will end up working out for you, but if you don't particularly care to pick up that new skill and the engine is out of the car, I would consider paying someone else to do it.

One of the things you have to watch out for when installing the crank gear is that the crank key doesn't slide back in the crank and form a ramp which the gear gets jammed up on. I actually split one of those gears in half that way about 15 years ago. Since i didn't have the puller tool at that time it was a royal ----- to go pull another one off a junkyard engine. Back when these cars were still in junkyards...

[marc]

One trick a welder showed me is to weld a washer with a inside diameter a bit smaller than the bolt to the broken bolt. Then weld a nut to the washer. Of course this only works if the bolt is flush with the surface. I've seen welders do some pretty amazing things besides joining two pieces of metal together.

[DevoBuzz]

It broke off about an inch inside the crank. Right where the thread starts. It seems like the crank gear was too small in diameter for the crankshaft. Were there dufferences in years for 87/88 and 89+? This is a forged crank.

Block is out of the car.

[4 l-bodies]

Ralph,
The early blocks had approx. a .900 size crank snout (along with TD blocks), while all the common blocks were around 1.00". Looking at the photo of gears, it looks like the early blocks had a larger snout diameter. Only the hub centric ring is larger, the actual snout is smaller than the common blocks. Then of course the CB have the smaller hub centric ring, but use the larger 1.00" snout.
I'm with Adam, my guess is what happened is what Adam was mentioning in previous post. They all have a small press fit, but should go on without too much trouble. I always turn mine in by hand (no impacts). That will beat up the #3 thrust bearing, and doing it by hand you will also feel the crank gear being pulled onto the crank snout, as well as feel it when it bottoms out. Make sure you have the correct crank bolt (common blocks used a different bolt than the early blocks), and I would run a tap through it to make sure threads are okay. You only want to do that once, and not have a repeat performance.
Good luck!

[tryingbe]

I think I broken a bolt before, but it broke outside the crank and I was able to get the rest out.

Every since then, I run a tap before I install the crank and use an all stud bolt, a washer and a nut instead of the factory bolt.

[4 l-bodies]

I think I broken a bolt before, but it broke outside the crank and I was able to get the rest out.

Every since then, I run a tap before I install the crank and use an all stud bolt, a washer and a nut instead of the factory bolt.

Ditto that for me too on the install. I also use some lubricant (STP) to help with the press. I also make sure crank and sprocket are free of defects, rust, galling, etc.

[DevoBuzz]

I definitely have the correct gear from those pics. When I put the gear on it wouldn't slide on all the way by hand. It started a little bit, but I needed the bolt to press it on. I used anti-sieze to provide some lubrication on the crank. After I took the gear off when the bolt broke, I noticed a ridge on the inside of the gear about 1/4" in that was not there before. It seems like the crack was too big for the inside diameter of the gear.

http://s1256.photobucket.com/user/de...55231.jpg.html

Could a crooked key cause that?

[4 l-bodies]

I definitely have the correct gear from those pics. When I put the gear on it wouldn't slide on all the way by hand. It started a little bit, but I needed the bolt to press it on. I used anti-sieze to provide some lubrication on the crank. After I took the gear off when the bolt broke, I noticed a ridge on the inside of the gear about 1/4" in that was not there before. It seems like the crack was too big for the inside diameter of the gear.

http://s1256.photobucket.com/user/de...55231.jpg.html

Could a crooked key cause that?

Could you have picked up a 88 2.5 TD crank gear? Looks very similar to CB gear but only has ..863 snout hole instead of 1.00". At this point I would measure the crank gear ID and the crank snout OD and see what exactly the press is. Should be around .002-.003 press.
Todd

[DevoBuzz]

The crank is 1.01" but now of course teh crank gear has a ridge so I do not know what it was before. But it seems close to that. Here are some more pics.

Sheared off bolt end. (Seems like it is fatigued to me. I would have thought it would be shiny where it sheared.)

http://s1256.photobucket.com/user/de...93434.jpg.html

Length of bolt now residing inside crank:

http://s1256.photobucket.com/user/de...94133.jpg.html

Actual crank gear - looks like the right one to me:

http://s1256.photobucket.com/user/de...80424.jpg.html

Depth of bolt inside crank:

http://s1256.photobucket.com/user/de...94350.jpg.html

I am thinking it was just a tight fit and a weak crank bolt is what caused it. Not sure why I got a ridge on the inside of the crank gear now though.

[Vigo]

I just checked all 3 style of 8v crank gear i have here and they ALL have that ridge from the factory. I never noticed it before but if i had to guess it's probably intended to let you spline onto the key before you actually have to start pressing instead of trying to hold it rotated correctly while pressing on at first.

[jeff1234]

If I had the problem I would try to find a drill bit with a carbide tip to drill a hole in the broken off piece. It shouldn't be that tight in there since the pressure is off the bolt. You could then wedge a screw driver or allen wrench into the hole and back the broken part off. Another possibility is getting a masonry bit which has a carbide tip and sharpen it the reverse of a normal bit. That way it would be drilling and nudging the bolt out of the hole at the same time. You would have to clean the threads frequently but that is what I would try before spending alot of money at a machine shop first if it were me. Taking apart a freshly assembled engine increases the odds of making a mistake during reassembly.

[Reaper1]

If you didn't use Loctite on the bolt, and it's not bottomed out, there should be very little tension on the threads. Provided the threads are ok, it might actually come out fairly easily with an EZ-out....if you feel froggy enough to try it....

[DevoBuzz]

Im gonna try a left hand drill bit first. If that doesn't work I will use the hole I drilled for a bolt extractor. <crossing fingers>.

Thanks for the info about the ridge Vigo. Never knew that was supposed to be there.

[supercrackerbox]

If you end up trying the bolt extractor, get a high quality one. The cheaper ones tend to break off, and then you need a very expensive carbide drill bit to drill them back out. Been there, done that.

[DevoBuzz]

Success !! Got it out using a left hand drill bit. Using a collar to center the bit helped. The threads on the crankshaft are nt too clean. Need a new bolt and m12 x 1.75 tap to clean up the threads.

[GLHS60]

Good for you!!

Broken bolts can be a huge problem.

Thanks
Randy

[Wastelands Warrior]

Hey Ralph we need to drink some beers to celebrate!

[135sohc]

Use a new bolt and cut some angled slots on it to clean the threads, a thread tap will only cut more of the thread out and make for a looser fit.