Rock_Six

LT1 smartones.

If an Opti-Spark is not tightened onto the Cam shaft properly, would that cause the bolts to shear off of the Cam Shaft? Could that in turn cause PTV damage? My mechanic will be sending pictures soon I hope. He said he took pictures of everything and has saved the bolts that were sheared off the cam shaft. The bolts were so loose that he removed them with his fingers, didn't need any tools to get the bolts out. The timing chain looks fine. Could this also be a result of a Non-Vented Opti being installed on my 97 by accident? (A new Opti was installed less than a 1/4 mile of drive time before this failure by a seperate shop, I am in Afghanistan) Would the longer (.700) Cam dowel with a Non-Vented Opti cause this sort of damage? 6 valves are damaged and I have 6 bent pushrods. I am tyring to figure out how that is related?

Injuneer

You can't accidentally install in unvented Opti in a 97. There would be no teeth in the hole in the cam sprocket for the unvented Opti's splined drive shaft to engage. The engine wouldn't run.

Rock_Six

Thanks,

I should have mentioned 95% of my mechanical knowledge is on LS1 engines. I just wanted to rule out all possibilities. So with that said, the only remaining possibility is an inproper install? Still puzzled how this resulted in damaged valvetrain.

Injuneer

Sounds like the cam bolts were left loose. There is no need to touch the bolts to install an Opti. A "too long" dowel pin would put pressure on the Opti, forcing the rotor into the cap, and likely destroy the Opti before it sheared three bolts off the cam.

When the cam stops opening and closing the valves, and the crank keeps turning, your going to damage the valve train.

shoebox

It might be worth finding out if the cam still turns freely by itself. If the cam gear bolts were not loose, sudden stoppage of the cam would be the only other thing I could think of that would shear off the bolts. I can't say I have ever heard of a cam seizing up, though. Makes you wonder if anyone played with the cam gear bolts when the opti was replaced.

Rock_Six

Guys, I am in Afghanistan and so it was the wife driving (First time ever driving this car too) Anyways, our mechanic pulled the heads and piston # 6 is cracked and the Connecting Rod is broken. This appears to have seized up the Cam which sheared the bolts off of the Cam Gear and the Cam Dowel. What I don't know yet as the pan hasn't been dropped is how the Crank and the block itself look. My chain survived, oddly. Mechanic is pulling the engine out this weekend for further inspection. More to follow.

Injuneer

Sounds like the crank is what stopped, and the inertia of the cam continuing to rotate sheared the bolts.

cnorton

I'd ask the mechanic to verify the condition of the rod bearings. Rods that are rotating freely on the crankshaft journals are not prone to breaking unless there are other factors present. There are multiple possible scenarios that come to mind including a spun rod bearing that snapped the rod, or a dropped valve that cracked the piston and jammed the rod bearing, or a hydrolocked cylinder from a leaking head gasket, or ???

I don't think they've reached the true core of the problem based on your information so far but whatever caused the problem should relatively easy to identify when all the parts are laid out and inspected.