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Alan L's Avatar
 
Join Date: Apr 2006
Location: New Zealand
Posts: 1,946
piston ring gap

I went to insert some new 930 rings in the cylinders. The spec sheet says max wear limit ring gap is 8 thou (0.2mm).

When I insert my new rings in the very top (unworn) and lower part of the bore, I still get 12 thou gap - how does that work? I'm reasonably sure the rings dont come in various sizes.
Alan

OK, I read the specs wrong - mixed up ring gap and ring clearance specs. 12 thou is in spec - just, for new ring.

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83 SC, 82 SC (After 10 yrs- finally SOLD to a good home), 82 930 (track) - Stock except for RarlyL8 race headers, 22/28 T bars, Digi WUR (currently in a box), Rarlyl8 Zork, modified 3LDZ, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)

Last edited by Alan L; 07-11-2011 at 04:53 PM..
Old 07-11-2011, 04:24 PM
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On two engines I've rebuilt, I used the old rings because they had smaller end gaps than the new rings I' had bought.

-Andy
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Old 07-12-2011, 09:51 AM
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On other engines I have done, you haveless than minimal gap and have to grind the ends to open them to minimum spec - with a special ring grinder stone.
So it does seem weird when re-ringing these things you have to start off with more than minimal ring gap - especially for a track machine. Squeezing up the ring gap to the bare minmum (which is usually a secret number to the engine builder) is one of the performance edges builders look for. But not an option here.
Alan

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83 SC, 82 SC (After 10 yrs- finally SOLD to a good home), 82 930 (track) - Stock except for RarlyL8 race headers, 22/28 T bars, Digi WUR (currently in a box), Rarlyl8 Zork, modified 3LDZ, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 07-12-2011, 11:17 AM
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Old 07-12-2011, 11:17 AM
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