Wednesday, October 18, 2017

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.

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