Crank Buildup... Again.

So, when I said earlier that the case was "torqued to spec" and that the crankshaft "didn't bind...." Turns out I lied. I didn't have two nuts on... and it turns out that those two little nuts caused a big problem.  Once I had *all* of the hardware on and torqued, the crankshaft stuck... pretty bad! I ended up doing a lot of digging, and it turns out that the piece that used to be the prop hub, which still provides a bearing surface, was the problem.

I started by trying different clocking orientations - pulling the hub, heating it up, rotating it slightly, and putting it back on - and I did find one position that was very close to perfect. However, it still had a sticking spot, and when I put a dial indicator on it, I could see why - while the hub was only out of concentric by about .0003, there was a single spot, like a lobe, that was more than a thousandth of an inch high. Now, I have a lathe, but I'm not confident enough in my abilities to do serious engine work. Nevertheless, I'm not willing to pay a machine shop another hundred to polish a single bearing surface into spec. 

So I chucked the crank into the lathe and set up to knock the lobe down with some emery cloth held in my tool holder, so I could just hit the high spot.

Once I thought I'd gotten close, I used some medium and then fine emery cloth to get all of the tooling marks off. Then I pulled the whole thing off the lathe and assembled and torqued the engine to spec again.



..........??????!!!!!!!!!!!!!!!!!!!!!!!

Rotates freely. Smooth as can be. I was pretty excited! It's still got contact across the whole bearing, too, so I didn't just turn it down so far it doesn't touch anything. (To give you an idea, I think I took about half a thou off of the bearing before I started with the emery cloth... so really, very long process for a very small amount of material.)

I cleaned the crankshaft up, re-lubed the connecting rods, and started to assemble them. Unfortunately, I can't find my LocTite to save my life. I think I left it in PA when I used it on my landing gear.

Yes, the connecting rods are pointing in wrong directions - that's just so the nuts are easy to get to. I couldn't just leave it all like that, so I went ahead and worked on setting up the distributor assembly. Because of the type of distributor I have, I don't think the orientation of the distributor drive shaft matters in the least. However, just in case I'm wrong, I oriented everything the way the book says to, marked it with red dykem, and put a holding screw in place to keep the distributor aligned correctly. I've gotta get a couple of new screws for that, though... these two are looking pretty buggered up.

I intend to assemble the crankshaft, then install it and the camshaft into the case, along with the correct end play shims on the flywheel, torque the case to spec and check free rotation one more time before the final assembly. If it all checks out, then I'll install the lifters, cam plug, and whatever else I'm forgetting, then put sealant on the case and bolt it all up for good. There's still a lot left to do, but this feels like a big turning point in this whole process.

Lathes + Flywheel Troubles

Having a metal lathe, even a small one, is a fantastic way to avoid paying a large amount of money for a small amount of work. I started by chucking up the crankshaft and adjusting until I had less than a thou of runout. That's still too much for bearing work, but I'm not doing bearing work. I put a 45º chamfer on the flywheel mating face, and knocked the burrs off of the pulley hub mating portion of the shaft. A little polishing to make sure the pulley hub slips on, and we're off to the races. The pulley hub was heated to ~400º F, the crank cooled to ~10º F. I still had to use some persuasion with a hammer to seat it fully, but she's on there now.

The two aluminum rings are the replacement seal housing, complete with seal installed. I must've walked through the assembly process a dozen times to make sure I put the seal housing on the correct way, and I still checked it half a dozen times afterwards. The red material is a cut up silicon baking sheet to help keep the rubber on the seal from melting/losing its elasticity.

After I turned the chamfer on the flywheel end, I re-installed the 4 dowel pins. The bottom pin in the picture is larger than the rest, allowing me to index the flywheel. My plan is to mark TDC on the flywheel, since it can only line up one way, and with very tight tolerances.

When I attach the flywheel and snug up the nut, I still end up with about .008" of runout at the edge of the flywheel. Not a lot, but more than I'm willing to put this together with. I used some more PlastiGage between the flywheel and the crank surface to make sure I was fully seating the flywheel... sure enough, I wasn't, and the place where I wasn't touching the crankshaft is the same angle where the flywheel is furthest out. There are four factors at play here; the crankshaft face, the dowel pins, the flywheel face, and the flywheel holes for the dowels. The crankshaft face is most likely true, since that's how it was run successfully before, and my PlastiGage test seems to confirm it. I proved that the flywheel face was true by using a rotary table and a dial indicator and getting less than a thousandth of runout. I think that leaves the dowels. How did that happen?

It happened pretty simply - I used the flywheel to drill the dowel holes. Normally, this would've been the best way to go about it. However, because of that radius on the flywheel that I chamfered the crank to match, the flywheel wasn't sitting quite right on the crankshaft, which means the dowels are *slightly* cocked to one side, which means they *want* to pull the flywheel that way.

So my next step is to torque the flywheel to spec, which is some ridiculous number above 200 ft/lbs, and see if that fixes the problem. If not, I may have to get creative. On a positive note, the only bit of clearancing that I still need to do involves grinding a little material off one of the connecting rods. Once that's complete, I can start setting things out for assembly. I do, however, need to get this flywheel thing straightened out before I can move forward.