Tuesday, April 1, 2014

Spare Engine - Block Inspection

Having acquired not one, but two spare engines recently which you can read about here and here. I needed to have a look at them and assess what kind of state they were in to plan what I was going to do with them.

One of the engines I bought on the cheap, having a cracked block is no good for a rebuild, but I will be useful as a learning engine and also for spare parts. This post however will focus on the 'good' engine that I hope to dismantle and rebuild.

Using my breaker bar and socket on the pulley nut, I rotated the engine which initially was fine, but did hit a sticking point which it could not get past. Trying a few times, it was obvious that something was jamming and stopping it rotating fully. Not the best of starts.

Removing the head quickly revealed the problem. There was quite a lot of rusty crud sat on top of the pistons. One was so bad, it was stopping it reaching top dead centre, hence the sticking. But once the head was off, the engine did rotate freely.

Crud in the chambers.

Checking the gasket and the top of the block, there was no obvious signs of cracking. The other engine had cracked between cylinder 3 and cylinder 4 where the metal is particularly thin. I found it easier to use some fine 'wet and dry' to clean the area between the cylinders to get a proper look.

A close examination of the cylinder wall surfaces show some areas for concern. There are still some areas where the honing marks can be seen, but there are also areas where the walls are corroded and pitted. Also, on the outside edges of cylinder 1 and cylinder 4, I can feel a lip, which indicates some wear.

I cleaned off as much of the crud as I could get at and poured some 20/50 oil onto the pistons to lubricate them as I turned the engine over a few times from the pulley. The oil has been sat there now for some days and shows little sign of leaking through, so maybe the ware is not too bad.

I cleaned up the gasket surface a little and covered it in oil for protection as it will sit there a while as I want to now turn my attention to the head and carb. Stripping these down will probably take a while and I don't want the exposed surfaces to deteriorate in the mean time.

Having no real experience of the inner working of engines, I need to seek advice about the things I have discovered. The pitting and wear may need a slight re-boring of the cylinders, but that would imply new oversized pistons and that is getting expensive. Or on the other hand, I might get away with re-honing.

Time will tell...

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