I've got a high-houred, early serial numbered 4020 that I'm using for field work. It runs pretty well, and everything works on it, but it seemed to be lacking power, it was blowing some white smoke and a lot of blow-by, and I found some coolant in the oil last summer. I decided to pull the head off as a winter project and have a look-see.The muffler is too high for my garage, so I had to take it off first, but it was rusted pretty good to the manifold. I removed the manifold and found that only one cylinder was producing all the white smoke, and as well, there was a pretty good deposit of thick black gunk around the same exhaust port. I've taken the head off and had a quick look at the valves and such, and really can't find anything out of the ordinary. Injectors look OK, but I'll need to get them tested. The head gasket came apart while I lifted the head off, so there weren't any clues there. One thing of interest is that I found remnants of diamond shaped score marks in a couple of the cylinders. Obviously from the last rebuild - but I'm surprised to see them still there, and on only part of the sleeve. And stupidly, I forgot to do a compression test before I lifted the head. Now I'm blind. Anyway, what to do next? I could take the head to a machine shop, but I'd rather not spend the money if I don't have to. I don't even know if it's bad or not. How do I find the crack where the coolant leak is? And what's with the hone marks in the cylinders? Did somebody just hone them out and not replace the rings? How do I check clearances between the valve stems and the guides? Thanks guys. Advice on where to go next? Alan
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