Bicycle Tutor

I have an old vintage lightweight and my BB is starting to click. It does not happen with every rotation, only when I'm putting pressure. Any suggestion on what I might try to stop it?
Thanks
Ian

Alex has a tutorial on overhauling bottom brackets, but I suspect something may have come loose in that area, or the bearings are worn. Either way you need to see his tutorial (note: it'll be overhauling bottom brackets, as i doubt you have a cartridge bottom bracket).
Have a go at that and see if that makes things better