So, I pulled the heads off my motor and in general there is little corrosion or wear and things look good, except that there is a 'probably significant' scratch at the top of number 5 cylinder wall. Since I am thousands of miles from a supply of good blocks I am looking at boring that one cylinder to first oversize. Seems doable: 928intl has the piston, and there is a shop here that seems to know how to do the the boring and lapping. But, I have euro S heads and cams (on top of a non S 4.5 bottom end), and I would kinda like to have the correct pistons/compression to match the top end. Plus I like the idea of new rings and the cost difference between the 95 mm rings and 97 mm rings would more than pay for the extra machine work, assuming:

1) I can find a used set of 4.7 euro S pistons for a reasonable price
2) The block can be bored out that far
3) The crank and rods are the same for euro S and non S

Does this make any sense? Is it possible?

 

Yes
Yes
Yes

 

It's an alusil block? So, it will need to be chemically etched to expose the silica like the factory does. I doubt a machine shop in Hawaii would know how to do this. Your better option would be to get it Nikasil coated, but I doubt again there is anyone on the islands that can do that as well.

 

quattro: Does it needs to be chem-etched? The WSM shows a boring and lapping procedure that looks pretty straight-forward, provided you can get the lapping compound. I notice that the discussion here seems to lean towards nickasil plating and steel sleeving and away from the procedure discussed in the WSM, but I am guessing this is about wanting to use different pistons or go to higher boost levels. The WSM procedure does not look or sound hard, and folks here (Ted's machine shop in honolulu) seem to know about it and have the equiptment. Is there some weakness or problem with the WSM procedure I need to know about?
mark: your website does not show used euro S pistons. Do you have them?

 

Karl, why'd you pull the heads? Bored? (no pun intended)

 

I do think lots of people are capable of doing it correclty. I'd visit your guy Ted and ask to see his hone and paste kit. If he has the correct Sunnen accessories and will read and follow the WSM than I bet he can do it properly.

 

I should have a set of good used Euro 4.7 pistons. Let me know when you are ready to order and I will dig them up.

 

Thanks, Mark.
For what it's worth, the story is this (copied from another thread):
I bought the cab as a basket case and one of the many problems was that both cam cover gaskets were streaming oil down on the exahust. I replaced the gasekets with the motor in the car and swore to never do that again. About a year later one or the gasekts started leaking again. I pulled the motor to replace the gaskets and while it was out I came across a mystery ebay motor for cheap. It had 4.5 non S numbers on it but I could see the heads and intake were euro S. So I bought to motor (and sold my old motor to bdangler) and pulled the cam carriers off so I could veryify that the heads and cams were S, but did not pull the heads. Then I put it back together with an new timing belt and a prayer. Once in the car it was clear I should have gone further. Uneven compressions and huge amound of oil smoke (although strangely only when going down hill). Then I moved for L.A. to honolulu and in the confusion of the move I forget to recheck belt tension after a few miles or so the way I usually do. So a month or so later the belt jumps and I bend a valve on number 1 hole.
So the plan was this:
-rebuild the heads (of course)
-install porkensioner (thanks porken,roger)
-install 16V'r adjustable cam gears with newer style timing belt (thanks, porken)
-install silicon pan gasket (thanks roger)
-install silicon hoses with an eye towards boost install (thanks, carl)
-pretty up intake, etc
-possibly do main and rod bearings
-install new brake master cylinder
-possibly replace coolant tank.
-install 928MS metal front shifter cup (thanks, carl)

Obviously now the plan has expanded to include fixing the block...

I generally try to avoid the 'while we're in there' disease, but in this case I am giving in somewhat. I have all the critical parts for the boost install, but want to see how I like the car as a well running S or S-hybrid before I go further.
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Remember there are two types of Euro S pistons, depth of the valve cut-outs are different (end therefore also the resulting compression)