Has anyone ever heard of this happening? What would cause this?

I thought I had spun some bearings but I was wrong!!! This explains why my car ran so rough with the timing being all off.

- 3 timing gear bolts sheared off in the cam
- dowel pin in cam was still in, but the hole in the cam is deformed
- #2-7 intake valves contacted pistons (not too badly though)
- looks like I spun some cam bearings
- timing chain shifted forward and cut a nice groove into the timing cover (fine metal in oil)
- no rod and main bearings spun


Thoughts???

 

never heard of something like this but at least you did not spin a bearing

 

I just found one other post that mentioned it happening. Maybe one of the bolts backed out a bit and then put more stress on the others?

I just wanna make sure I can avoid having the same thing happen again.

 

As already stated more than likely at least one bolt backed out causing excessive vibration and the other two followed suit. The solution is to use loc-tite (I use red) and and torque to proper spec.

 

Also it's a sure bet that the valves that hit the pistons are probably bent.

 

If you had bearing problems on the cam, like you say, it could have seized when it got hot and sheared the bolts off.

[edit] Got an email below from a non-member after seeing this thread. He wanted to supply some info:

 

That is a good point about the cam seizing

 

i didnt fully shear mine off but close. i believe mine was caused from excessive vibrations after two lifters spun. i would guess on the side of a loose bolt backing out though.

 

All my lifters seemed fine

 

i had it happen before...its becuase they need to be torques specifically...i figured tighten them but they are very specific...i had 3 break off on me but it was my own fault

 

If my pistons contacted by intake valves, there is probably a good chance that they are bent, right? And if they are, my pushrods that go with those valves probably are too?

 

Yeah most likely. Only way to know for sure is to check.

 

i had the same thing happen to me on a motor that to the best of my knowledge was never taken apart. My valves were bent so i had to pull both heads and take the oil pan off to get all the pieces cleaned up. i never determined a cause or had any signs that it was going to happen. Mine let loose during a wot pull at about 5k. i put new valves in and had the heads checked and put it back together and never had another problem.

 

I had this happen on a standard sbc.
The key way was broken on my balancer, and it started to walk. we could never get the timing set right. it was slapping the lower gear and I managed to make it home w/o major damage. I could hear the balancer trying to come off, but at the time didn't realize thats what it was, sounded like a bad powersteering pump.
The cam bolts had backed out and started to shear.

 

This thread is freaking me out....I just figured out yesterday that I have been driving on an U/D pulley without a damper for over 3 years ---