Seized for a moment at startup. Plooms of smoke.. any ideas?
 

I recently posted a thread about getting my coolant temps down and fixing the A/C, but about three days after that i drove the car to work and it was running great. parked it. and when i started it up to leave about 9 hours later all i got was a strong CHUUNK sound that shook the whole car. tried again and CHUUNK! 3rd time i tried starting it, it turned over and ran very strangely. My v8 felt like a 4 banger with a miss in 2 cylinders. and i had white smoke pouring from the exhaust. At first i though i had somehow spun a bearing or something or wasted my head gasket or cracked a head but there was no knocking and when i smelled the smoke/vapor from the exhaust it didn't smell like burnt antifreeze at all and i am familiar with the smell of a blown head gasket or two. It smelled like oil. I figured i was screwed and it was time to tear it down and see what happened. I thought, well if its a head gasket failure and its burning and its pumpin out white smoke from the exhaust then the car will overheat if i let it run for more than 5 minutes. It did not. I let it run and it maintained op temp and gradually regained power and white exhaust faded and eventually was gone after about 15 min. And has been running fine ever since.

I have no idea what would have caused this to happen. Why out of nowhere,only time and has not happened since? It's like oil found its way into the cylinders as the engine cooled throughout the day. The only thing i can think of that i've done different is about a week ago i switched to full synthetic oil. Other than that i'm at a loss for what could have led this to happen. It has ran perfect ever since but i am hesitant to drive it fearing it may grenade on me while i'm out on the road. Any ideas? Suggestions?

Re: Seized for a moment at startup. Plooms of smoke.. any ideas?
 

Probably a small head gasket leak causing coolant to leak into a cylinder. This can cause random starting issues depending on where the piston stops in the bore when you turn the engine off. If enough coolant gets trapped in the cylinder, the next time you start it, it's not going to want to compress. Broken starter or even a bent rod can result. Check and see if you have any "clean" plugs that would indicate coolant leaking into the cylinder. It's possible to have a head gasket leak that goes into the combustion chamber and not into the oil.

Re: Seized for a moment at startup. Plooms of smoke.. any ideas?
 

So if i check the plugs and they look to be okay (not washed looking) whats next? Compression test?

Re: Seized for a moment at startup. Plooms of smoke.. any ideas?
 

Sounds like you hydro locked the motor with coolant in the cyl

As noted if this is the case you can often break a starter or bend a rod trying to start a hydro locked motor

...or pull all the plugs and crank engine over a few turns...is coolant coming out one of the plug holes???

check for coolant in oil

Re: Seized for a moment at startup. Plooms of smoke.. any ideas?
 

Hydrocarbon test would be a good idea, but if you had that much white smoke, you probably will find at least one cylinder different.