So yesterday was a long day. I spent the whole afternoon polishing the crank. My arms and shoulders are still sore. All of the scoring and almost all of the pitting polished out but the areas where galvanic corrosion had set in are just too deep for me to polish out by hand. I mic'd everything when I was done and I had taken .00075" of material off. The corrosion looks to be about another .001" deep. That is good and bad. It looks like it can be polished out and still be within the wear limits but I was hoping not to have to take that much material off.
I had a chance to finish cleaning up the piston and get a mic on it. I found all of the wear I had been expecting when I tore it apart. It was all in the piston. This is a .010" oversize piston and I measured 4.504"/4.503" on the skirt and 4.494"/4.4935" above the top ring. So, that's .006" wear at the bottom and .0165 wear at the top.
The wear limit is .005" so it is well out of spec. Between the wiped out rod bearing and the loose piston I bet this engine was making some serious noise when it was shut down for the last time. I went through a few of the other parts and found a few more pieces that have enough wear in them to be of concern. The cam being the worst. It is pretty loose in the bushings and is worn enough that it may be time to replace the shaft.
I also rechecked the cylinder at 38ac's suggestion. That is where I did find some good news. I can still see crosshatch all the way up to the ridge. I checked about 20 different places and concentrated on the first inch directly below the ridge and I couldn't find anywhere that varied outside of 4.512".
I have been contemplating my options and these are what I have come up with:
Option #1:- Have the crank polished until the corrosion is gone and run it if it is still within the wear limits.
- Replace piston and rings with a new .010" set(if I can find one) and deglaze the cylinder.
Option #2:- Have mains polished and run them if they are within wear limits.
- Have crank pin turned .010"
- Have cylinder honed to a uniform 4.512"
- Replace piston and rings with a new .010" set(if I can find one)
Option #3:- Have mains welded and ground to "as new" spec.
- Have crank pin turned .010"
- Hone cylinder to a uniform 4.512"
- Replace piston and rings with a new .010" set(if I can find one)
Option #4- Have mains welded and ground to "as new" spec.
- Have crank pin turned .010"
- Have cylinder sleeved back to std.
- Replace piston and rings with a new std. set.
Option #5- Replace crankshaft with an aftermarket one.
- Replace cylinder with and aftermarket one.
- Replace piston and rings with a new std. set.
I am thinking somewhere between option #1 and #3. I aim to do this right but it is a question of how far do I need to go for it to be "right". I plan for this engine to be a power source while I build my next place and then serve as a back-up generator. I figure option #1 would buy this engine several thousand hours of service which is likely more hours than I would ever put on it. But, option #2 seems like it is probably the minimum to do it "right". Ultimately option #3 would get this engine as close to "as new" spec as possible while saving the chrome bore and the original English parts which I would prefer.
I won't have any time to work on it for a few days and need to see about tracking down some parts.
So, what do you guys think? Opinions would be appreciated. Which direction would you go?