Update from the shop - he pulled the oil pan and did some looking around and he's quite convinced it dropped a valve and then the engine grenaded from that. He said not due to oil starvation. He's not sure (nor am I) as to what would have caused a valve to drop. In 7+ years, that engine was only redlined once and that was for a nano-second and was probably 4 years ago. The morning this happened, i was passing a car on the highway, but was definitely not exceeding 5k rpm's during the couple seconds it took to pass the car. As i said earlier, it's always been babied ... maybe too much.

Also, the flex plate it toast, but other than that, the shop says my Z should be ready possibly be end of day tomorrow.

Any guesses why valves decide to drop themselves into a cylinder?

We'll update when i get my Z back.

Our engines dropping valves is not normal at all. If you did have piston to valve contact it may be due to the galley gasket leaking oil. It supplies oil to the VTC's on the cams. Normally that won't cause any piston to valve issues unless the timing chain jumped or broke. That diagnoses is lacking lots of information. Something else was missed.

Thanks Spooler. So maybe the timing chain broke causing the valves to go nuts. I guess then the question is why would a timing chain fail at that mileage on the VQ37? I've not heard of that happening on our engine.

The shop didn't do a full diagnosis - I would have had to pay for a bunch more labor. He just did some of his own (without charging me) based on his curiosity.

Yeah, he would need to have pulled the front cover off to look at everything. That might have given him more of a clue.

:iagree:
He would have to tear the motor apart to see what really happened.

I had one motor drop a valve for no reason once. Another motor, I had a Crane triple valve spring break and hold the valve part way open. Lucky, it didn't do any damage.

Got my Z back on Saturday. New long block, flex plate and intake manifold. Needed the manifold because it was polluted with shrapnel from the engine grenading. It really looked like someone dropped a bomb in there. There would have been no way to clean it out. Total price with labor $6485.

Drove great on Saturday. Only did 15 miles as the weather sucked. However, it has a couple oil leaks so taking it back in the shop on Wednesday to have that taken care of. Hopefully easy fix.

Keep us updated and glad you decided to keep it. :)

I have never done a study on engines that have dropped a valve, but I believe there are 2 common types.

First is it broke at the lower notch of the valve stem where the retainer latches. This can be explained by micro cracking during the manufacturing process. Whether it's inclusion in the material or surface scratching, your guess is as good as mine. This fails catastrophically without warning.

The other type is caused by excessive wear on the stem as witnessed by the recall on GM LS7 engines. This creates a valve train noise that develops over time. Hard to tell and it requires trained ears to detect without opening the engine.

I have experienced a valve dropped on my '82 Toyota Land Cruiser FJ40. Luckily, it happened at a red light while idling. The engine simply stalled and refused to turn over. Opening the valve cover revealed the cause and after a new valve, lapping of only that one valve, and reassembly, the engine was back. A tiny nick on the piston and on the head were all the damages left inside the engine. In a way, it was a lucky engine.

At any rate, I'm glad the car now is running again. Hopefully the oil leak is a simple problem that can be easily fixed.

Final update as now have my Z back with the leaks fixed. Runs great ... this car seems so fast after driving my Wrangler for the last month. While the Z was being fixed this last time was actually considering going with another sports car, but after driving it the last couple days, it really is a cool car ... just hoping the replacement engine holds up well. Thanks to all for your help on this thread.

:tup:

Keep your receipts and stuff in case you decide to sell it ever! :D

Glad to hear it worked out!!