1quickTA

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???

TBSPW

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

1quickTA

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.

SS RRR

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.

The_Bishop

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

shoebox

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:

1quickTA

That is a good point about the cam seizing

FlamingChicken

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.

1quickTA

All my lifters seemed fine

Daniel6718

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

1quickTA

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?

Dave1980

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

Black6spdZ

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.

BigBadBlack93Z

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.

AlwaysCode390

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 ---