Bad squeaky sound, probably bent crank (3.0L)

[jangell]

About a month ago I took a break from my working on getting my 3.0L swap running to replace the entire A/C system with the help of a friend of mine (who is an actual mechanic, mostly working on classic cars). When it was time to fill the system, we tried cranking the engine and got this horrible squeaking sound. Our assumption was that the flex plate bolts or torque converter bolts were scraping against something. We confirmed the sounds related with every revolution of the engine by looking at the missing tooth gear on the crank pulley.

~10 second video of the noise: https://youtu.be/vvou5ZHh1tc

At one point, we looked up through the inspection hole in the automatic transmission and noticed that the flex plate is moving in and out, implying that it isn't seated correctly.

~6 second video of the wobble: https://youtu.be/9UqkfG25lPA

So we pulled the motor, leaving the transmission in the car (my friend is confident that it won't be that hard to reattach; I'd have pulled the engine and trans together, but hey). We checked the flex plate with calipers against a flat surface and found it to be pretty much perfectly flat. When we remounted the flex plate (which sat flush against the crank), we noticed it seemed slightly tilted, like the top was closer to the engine than the bottom.

IMG_0752.jpg

We tried turning the engine with a wrench, and got the same horrible squeaking sound, even without the flex plate attached. Measuring with calipers after rotation the engine in 60 degree increments seemed to find a deflection of about 0.26mm (not that I'd necessarily trust the measurements, but it fits with the very slight tilt of the flex plate).

At this point, we're assuming the crank is bent. How this happened is unclear.

This engine has never been running, not completely. I have turned it over by hand before putting it in the car (it was tough at spots, but that was just the engine compression -- our attempts today seemed much tougher than that). I had also cranked it with no issues. I had gotten the car to run very poorly with MegaSquirt for some initial testing (forgot to connect MAP, only two plugs were firing, timing way off, etc), but never heard this noise.

In fact, the noise only started after we replaced the A/C system. We did not turn the engine at all during that process. We raised and lowered the nose of the car, but that's all we did. It seems unlikely that we knocked something loose or out of alignment in the engine simply from that.

My friend assumes me that the untuned engine didn't bend the crank, as it is more likely that I'd have destroyed something else before the crank bent. He thinks the engine was overheated by the previous owner (it had 35k miles, according to the junkyard, and was working), and that this softened the metal enough to warp it slightly. But I can't explain why this noise suddenly started happening. I didn't think to look for flex plate deflection when I put everything together in the first place, so I don't know if this was present before.

Next weekend we'll likely tear down the engine, and I'll be hunting for a new 3.0L to install in its place. Luckily the amount of work here is only a small part of a 3.0L conversion, although obviously not a trivial amount of work. Hopefully it'll go fairly quickly.

Mostly I was wondering if anyone had seen this sort of thing before. It's very odd.

Thanks!

-- Joe