New engine stripped

[Jonny69]

Don't you love the way cuts are a cut one day and a weeping sore the next? A burn on my finger from a hot header was quite happy being a burn until I had to squeeze something in the garage and the skin split. Kind of knew it was going to happen because it's on the back of a knuckle so I can expect it to happen every time I bend my finger. Mmm it's oozing.

Bit of background because the engine in my spam-tin mobile did expire and I don't think I helped it by 'fixing' it with Radseal. The headgasket was blowing between two bores which you could hear, but it was also weeping a lot of water out the front of the block. I hit it with the Radseal to stop the water so I wouldn't have to change the headgasket to stop that but actually it was where two of the head studs had worked loose. Once the Radseal was in there the water stopped but I then couldn't crank the head down properly! I guess it's the risk you take when you just fire up a 50 year old engine without knowing its past.

Stripped the new engine down anyway, the only bit I haven't got out now is the cam and valves because my valve spring compressor isn't skinny enough to go in. Was thinking about chopping it up but I think I might just look in 'frauds first because they do a whole range of tools like that. Diddy little pistons on the ends of really long thin weak feeling rods. You know when you get poor quality cast metal and it kind of feels like it's made of brittle toffee... that's what these feel like. Shame I don't have a lathe or mill because there's loads of meat that can come off the pistons. The crown can lose at least 2mm and down on the skirt there's about 15-20mm of excess length that could come off. You'd probably get a bit of piston slap but that's no problem. I reckon on the breathing you could get a 1mm larger inlet valve in there but there's not much space for a bigger exhaust, but to my eye the ports are quite adequate for that size engine. It's just the tiny strangling carb that holds it back!!! I added some extra rounding to the tops of the bores as they didn't quite go to the edges of the chamber and were a bit sharp which defeats the point of doing that. This is to promote flow on a sidevalve engine.

Basically apart from a tight valve it doesn't look like the damp in it has touched it at all, there's a bit of corrosion in the middle of the centre crank journal where the oilway runs round but that will wet and dry off and not affect it at all. Big ends and the shells are all fine, despite running round a bit dry where I've been turning it over by hand. One ring has been gapped up a bit wrong, it's gapped open about 15mm so that will blow through quite a lot but I don't know where you buy piston rings from, especially just one of them.

Like I said shame I don't have a lathe and mill and some time really, you could turn that thing into a right little screamer with a bit of cutting here and there. I reckon you could lose at least 50 grammes off each piston and the valvetrain is so light on that thing. Turn up some really skinny stainless valves, machine the head down a bit more to suit. I'd love to cut a crank up as well, I bet you could offset grind it and use oversize big ends.