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96mm pistons In This Motor? Good/Bad?

Anyone know what brand/compression ratio/quality these are?











There are the following markings on the bottom of the piston, cast in "L" and "2". Across from the arrow on the face is a "2" in ink. The cylinders have red dots on them.

My cheap caliper shows 96mm BIG BORE?

Sorry for reposting, but I could not change the subject.
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Old 12-23-2002, 04:21 PM
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DuckRyder,

That steel strip cast into the piston looks familiar. The pistons might be from the old Japanese NPR bigbore piston/cylinder combo.

Measure the ring height- that's a clue. I have an old Automotion (or Tweeks) catalog somewhere that listed the difference between stock rings and the fatter NPR rings (Deeves ring section?). The catalog also showed a picture of the bigbore set with one of the pistons stuck at an angle in the cylinder.

The NPR cylinders were cast iron and are rough on the fin surfaces. The cylinders also had a narrow "knife edge" section at the top of the cylinder (where it goes into the head).

If they are NPR's, then they were sold as being of "consistant quality". I believe Jake commented that the NPR's measure better than some of the non factory stuff out there today.

Hope this helps!

Ken


Old 12-24-2002, 06:30 AM
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Found the bill for them. Dated 1987. From a Porsche supplier hand written and says "2.0 P/C - $250.00"

I'll try to get hold of the place and see what they say about what brand they would be after christmas.

Cylinders are rough and iron.

Do not appear to have a knife edge.

I make the two top rings as 1/16th and the oil ring as 5/32nds
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Old 12-24-2002, 02:00 PM
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Rats, wrong thread
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Old 12-24-2002, 10:03 PM
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Robert,

Found a late 80's Tweeks catalog (God, am I a packrat or what!). The piston picture in the catalog appear to be identical to your pistons, that is a mild dish on the top and the pair of holes flanking the piston pin bore.

The piston/cylinder kits were offered in 1.7 and 1.8 stock sizes and in big bore kits to bump the 1.7L or 1.8L to to 1920cc, and the 2.0L to 2100cc. Prices ranged from $170-$300. I seem to recall that the big bore kits put the 1.8L C/R back to around 8.2.

The only reference to ring thickness was a "2x2" for the 1.7. Must have seen the other height list in the Automotion catalog.

As per the knife edge on the top of the cylinder, the NPR's were thin (compared to stock) so they could fit the 96mm bore into the stock heads without any machining.

You gots NPR's dude,

Enjoy!

Ken
Old 12-25-2002, 07:36 AM
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SO you have a short stroking 2.0L So what length of stroke is this engine. 71MM is 2.0L with 94 Pistons or 2056cc with 96 pistons.
Old 12-25-2002, 03:16 PM
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The case has never been split, it's a stock 2.0 bottom end, so with the 96mm X 71mm it's a 2056.


So NPRs are cool? I'd be O.K to put it back together with these after the heads are fixed? or should I spring for new Euros?


I may split the case and replace the bearings and cam, I only want to do this once, so I want it right when it goes back in.
Old 12-25-2002, 03:38 PM
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NPRs are supposed to be good stuff. I don't know how you ID them, though.

The "knife edge" was only on the 96mm cylinders that fit the 1.7 heads; the ones that fit the 1.8 and 2.0 heads have a decent cylinder wall thickness.

--DD
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Old 12-25-2002, 08:10 PM
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