I can't believe it's been nearly a month since I last posted on this rebuild. A combination of having a short holiday, being pretty overwhelmed with work, and poor weather meant the project stalled for a bit !
With the weather still being potentially changeable (as in bright sunshine to heavy showers with only 60 seconds warning), I didn't attempt anything too ambitious today.
The goal is to get the stuck pistons moving. I expect this to take a while ! If you look in my previous post - HERE - you'll see how awful it looked when I first opened the engine up. I've had them soaking in engine oil for about 4 weeks, to see what that did. This is what they looked like after most of the excess was removed;
Pistons 1 & 2 - quite a bit of debris, but the liners not too bad
Pistons 3 & 4. 4 is good, 3 is a wreck with a LOT of rust on the barrel
I wanted to find a way to turn the crankshaft with minimal risk of further damage. I suspect the nut on the right may already have snapped the timing locator pin.
So I decided to remove the alternator cover. Partly because it would allow me to see what it looked like in there, and also because the alternator rotor is a nice big lump of metal I can grab to try to turn the engine over.
Getting the cover off was a bit of a challenge in itself. In the photo below, you can see the hollow steel dowel at bottom left. It was stuck fast to the cover and engine, thorough a combination of galvanic corrosion and rust.
Freeing it up took a combination of lots of WD40 and wiggling of the casing, followed by some light taps from a rubber mallet on the lower front of the casing.
That enabled me to open up just the tiniest of gaps, and I was then able to lightly tap first the edge of a penknife and then the tip of a screwdriver into the gap. All the time, I was being as gentle as I could be to avoid causing any damage. This is definitely a job where using the minimum of force and the maximum of physics is what works best !
The alternator rotor (above) has some surface rust on, but nothing to worry about. At a later stage I'll probably clean it off and apply a very light smear of oil or WD40 to protect it.
The cover with the alternator stator in (above) is in really good condition. No sign at all of damage to the copper wires of the stator, and just one allen screw which has gone rusty. Considering the age of the engine, I'm really happy with the condition of the alternator.
Turning back to the pistons....
I am convinced that at least one, and possibly as many as three of them, are stuck because the piston rings have rusted themselves to the barrel liners. The real task is to get them freed up so I can remove the barrels and pistons and put replacements on.
Refurbishment would likely involve having to replace at least the liner on number 3, over-boring the lot and sourcing over-sized pistons and rings. Not easy or cheap for an engine this age ! I do have a set of barrels which should be easier to get usable with just a good honing, and two or three sets of pistons I can find the best fitting ones from.
But it still means getting this lot off first ! In a worst case scenario, I could open the bottom end up again and take off the big end caps so the pistons came out with the rods still attached. But I really, really don't want to do that unless there is no other way. Disturbing the big ends is a last resort.
So the first thing I did is clean them by squirting lots of WD40 in. This blasted out loose particles and held them in suspension in the oil. I could then soak up the WD40 and floating debris with kitchen towel and use an old blunt needle file to lift carefully lift loose bits out. After a couple of hours of careful work, it looked like this;
Still not perfect, and no movement whatsoever at the crank, but at least there's less debris and crud that might fall in and damage things. The crowns of the pistons are a lot cleaner, but that's kind of irrelevant right now !
Number 3 is really bad, however. It's a bit hard to see in the photo below, but the barrel lining is incredibly badly rusted, with flakes lifting off it - probably more than just honing can deal with.
The last job for today was to fill each barrel with white vinegar. This will break down rust, and also tells me a bit more about what is going on. Below is the photo with the vinegar in.
The idea was to leave it for 2-3 days to gradually eat away rust. As it was, piston 2 surprised me as the level of vinegar dropped half a centimetre in the course of an hour.
What this tells me is that the piston rings are not rusted solid, because if they were, none of the vinegar would have got through. But also that the rings are still there and doing their job because they stopped the vinegar from just running straight through.
It's a shame the other 3 pistons aren't so hopeful. I cleaned out number 2, and sprayed it with WD40 to stop any new rust forming. I'll check again tomorrow to see what the other three are doing !
