(I make the distinction between Genuine and Indian because there might be a difference)

I am needing to refurb by old CS cylinder head. Unfortunately at some time in the past, I suspect there has been a persistant head gasket leak which has allowed water into the combustion chamber resulting in erosion/pitting of the head, particularly around the mouth of the combustion port extending up to the edge of the cylinder gasket ring (IYSWIM). Skimming 40 thou would improve it a lot, 80 thou might just clean it up altogether BUT what is likely to be the safe machining limit?

If anybody has any practical experience to share I would be most gratefull.

8/1 cylinders had exposed cylinder studs and 600/650 rpm engines had the studs pass through the block.If using an alloy piston in a 6/1 then you need to use an 8/1 bump height (cylinder head clearance) re expansion of the piston when hot.

That sounds like it. The studs are visible along the body of the block passing through "Flanges" at the top and bottom (IYSWIM)

I have also done a little checking and conclude that the iron piston is several pounds heavier than the alloy one so a new piston might well be a good idea.

Unless anybody knows better. I cannot think of any particular reason to change the block. Some of the originals might have been chromed but I doubt if any of the Indian replacement ones are. (In fact the spares shop only offers a choice of "Old" 7 stud and "New" 5 stud) and it otherwise seems in good condition (There is the "slightest" of ridges at the top, barely noticable with the edge of a finger nail. Nothing a light honeing wont fix!)

As Potter points out, the 8/1 had the alloy piston and the four-ring configuration. Does the engine plate have 650 rpm?  Sounds like you may have a 6/1 engine with an 8/1 cylinder and piston.

It is definitely a 6/1 650RPM engine. So that sounds likely. As I said, the block has been replaced so it wouldn't be surprising if a "new" piston came with it. Appart from this the machine appears to be complete (IE all the various serial numbers match up with one another)

Would it be advisable to replace the piston with a 6/1 one?

Yep, sounds like heat exchanger is the way to go! 

Another thought that occurred to me  (since the amount of heat coming off the cooling system is unlikely to be that large. it is only a 3 Kw gen after all and I wont necessarily be using all of that all the time) is that the cooling water could be circulated (at low pressure) around its own heating loop with one or two domestic radiators of suitable capacity with an additional fan driven car type rad outside the house if the temperature gets too high due to lack of heat demand (House up to temp)

Said loop could be filled with antifreeze mixture!

An exhaust heat exchanger is of course a different issue! Here's a simple plan that I found that a reasonably competent welder should be able to follow.

http://www.volvoxengineering.com/images/heatexchange.pdf

Thanks for that, I had figured that this would be the case but wondered what other peoples experiences might be. (Good or bad...  )

 

Well, I have done it.

I am now the proud owner of a complete CS 6/1 SOM.  (IE it includes the separate controll box that is so often missing!)

I bought it off E-bay (UK). some might think that I paid a bit over the odds but the difference between a "Fair" price and what I paid was only a couple of hundred quid at the most and in the great scheme of things I reckoned that it was more important to have a complete system. the real expense will come later as I restore it to reliable operation.

I only had a small trailer to recover it and I actually think I was Lucky that it didn't collapse under the weight getting it home   (No seriously! I had considered that the 6/1 was 330KG and the cast iron base not more than 150 KG. Now I read that the SOM engines are actually nearer 500KG owing to somewhat heavier flywheels. The weight of the base I do not know!  The generator was removed and put in the back of the landcruiser to reduce the load on the trailer but it still must have been somewhat more than the 500KG rated load capacity!)

Thus far I have not even got it off the trailer (This will be fun) It turns over smoothly but I am clearly not getting compression (My guess is that the exhaust valve is not seating owing to it spending the last 5 years open on the decompressor)

I have no real issues with getting the engine to work but I am more concerned about the SOM alternator and controll boxes. The controll boxes both require complete restoration/rewiring and the cables between the alternator and the top controll box are in poor condition (Insulation brittle and cracked)


I would be gratefull if anybody who has had experience of repairing the controll boxes and alternator would be willing to share their experiences.


Photos to follow!