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Old 01-09-2016, 12:32 AM   #1
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Default Wiseco piston ring gap (2nd ring oddness)

Went with wiseco 84.5mm pistons on my rebuild, using good old 8450xx rings. Was going to gap them to the street moderate turbo recommendations from wiseco (.050 x bore top, .055 x bore 2nd ring), rounded up to the nearest increment that the feeler gauges can measure, which means .016633 top ring (rounded up to .017) and .018297 2nd ring (rounded up to .019). Sound good so far?

I took the rings out of their packaging, squared them in the bore and took an initial reading of end gap. The top rings were all way under target, but the 2nd rings were all a bit over.

Cylinder 1
Top: 0.011 Bottom: 0.020
Cylinder 2
Top: 0.011 Bottom: 0.019+
Cylinder 3
Top: 0.011 Bottom: 0.019+
Cylinder 4
Top: 0.011 Bottom: 0.019

Obviously, the .011 top ring gap I can shave up to .017, but the .019-.020 can't be reduced.

Thoughts? My feeling right now is that it's only a tiny bit over my target for the 2nd ring so it's fine as is. I suspect wiseco may have done this intentionally to prevent people from ending up with a smaller 2nd ring gap by accident.
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Old 01-09-2016, 08:46 AM   #2
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You will be fine with a gap that is on the loose side for the second gap. And it is ALWAYS better for the ring gaps to be slightly too loose than tight.

The reason the second gap needs to be loose is to allow the gasses that end up trapped between the top ring and second ring to have a place to escape.

If the gasses get trapped are spent air and fuel...it can cause "ring flutter" not terrible but not great either.

If the gasses are unspent air and fuel and they are ignited....well that's how you blow ring lands out of pistons.

You are fine with those gaps. but GREAT question.
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