> I was at the machine shop the other day discussing work on my TR6 engine
> block with the machinist. He looked at the bores, felt the top
> for a ridge,
> and observed that the cross-hatch pattern was still visible. From this he
> concluded that it just needed honing.
>
> Now, I'm not experienced with this, but shouldn't some
> measurements be made
> to confirm this?
Hugh :
>From your description, I agree with your machinist. The maximum wear in the
bore is right at the top, so the size of the ridge is a very good indicator
of overall wear. And an experienced machinist can easily feel the
difference between .002" and .001". Likewise, the cross-hatch pattern is
very shallow, only a few micro-inches, so you know the wear is less than
that where you can see the pattern.
All this assumes, of course, that someone else hasn't been mucking about
with your engine, but it's usually pretty easy to tell.
> Also, I see reference to +.010 rings, but nobody stocks them.
> Would these be
> fitted to standard sized pistons? Oversize pistons start at +.020.
+.010 rings would normally be used with +.010 pistons. The lack of one is
probably the reason for the lack of the other ...
> Finally, what do I do with the piston/bore grade data that Bentley refers
> to? I assume that you match A pistons to A bores. Correct?
IMO, ignore it. The grades were a way of dealing with the machining
precision of the time, modern parts should be identical within .0002"
(unless they were machined by me <g>)
Randall
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