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bdonally bdonally is offline
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Join Date: Dec 2001
Location: Off grid in Eastern ONtario
Posts: 209
An unpleasant finding

I was pretty sure the pistons and cylinders were good.
The pre-teardown leakdown test was good - all less than 3%.
The rings look great, and the piston grooves are well inside the wear limit.
Measurements of the bores shoed a bit of taper and ovality, but well within spec.
Piston to bore clearances showed some wear but clearances are all 0.06 to 0.08mm.
Based on that I decided that while new would be nice, I could get another few years out of the parts.
Then I found this in one of the cylinders:


Blown up it looks like this:



Looks like some platingcame loose and left a little island in the middle.
its about 2mm across.
And the scratch can be felt using a fingernail.
Also, while the original crosshatching is evident, only the deepest parts remain - the rest of the surface is very smooth.
Sorry about the photos - its hard to get inside the bore
So now it seems my options are to
  1. ignore it and hope for the best
  2. get that one cylinder replated - that seems a bit mickey mouse
  3. get some new 95mm P&C - possibly used. Used seems to pose as much risk as using the ones I have. New ones could be either Mahle or JE pistons/my cylinders reworked
  4. new 98mm pistons - likely JE + reworking my cylinders.

I like the way my engine works.
I'd be interested in comments about the 3.4 conversion, using stock cams, but updating the chip. With my current setup, I was showing about 215 rear wheel HP , so I suspect I'd get a bit more. I don't really want to change cams because I like the torque profile I have now.
What would you do??
__________________
Bob D.
'84 Carrera - MAF, Wong chip, RSR flywheel, ER bushings and other bits, CTR fiberglass F/R bumpers, 7/9 Fuchs, 22/27 TB, 22/21 SB, bunch of other little stuff
'69 Lotus 7 Series 3; '74 Fiat X1/9
'14 X5 diesel
Old 06-26-2018, 02:57 PM
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