I think I'm missing a nut.

RustyRatRod said
225. I cannot remember, but it is the same as one of the V8s. I THINK it's a big block, but I wouldn't swear to it. The one Charlie posted above will do it. I just happened to have one in a bucket of bolts. I don't know for sure which engine it came from. All of the slant sixes take the same size bolt, though.

Just bought this at the hardware store. It is a Grade 8, 3/4 - 16 bolt that is 2 1/2" long. I just put it on the engine and it threaded on just fine, but wouldn't tighten all the way down. The second photo shows that I couldn't get it in any farther than in the photo. Any ideas? BTW, the good news is that the engine is not locked up and rotates. I hope I'm turning it in the correct direction (counterclockwise as viewed by the driver).