Ring gap

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Feb 25, 2012 1:30 pm

Started putting my over bore pistons in the re-co block & found the new rings have a gap bigger than the upper limit of the factory manual gap.

My question is should the overbore gaps be the same as standard ring gaps or because of over-bore should the gap be larger?...[i personally don't think so but not sure]?

Keith Jones · Post by **Keith Jones** » Sat Feb 25, 2012 1:47 pm

Gary
The ring gap is usually proportional to the bore, so an overbored piston will have a slightly bigger gap.
The rule of thumb is .004 times the bore for road going engines and .0045 to .005 for sports engines. This is for the top ring.
What is your overbore and what are the gaps?

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Feb 25, 2012 3:30 pm

Hi Keith

Top ring gap is 0.45mm [factory spec 0.15-0.30mm]

2nd ring gap is 0.45mm [factory spec 0.15-0.30mm]

oil ring gap is 0.8mm [factory spec 0.2-0.7mm]

squigly oil ring gap is no gap & tight..[needs filing? no spec stated]?

Overbore is 0.5mm

Sorry but my measurements are metric & yours are imperial!

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Feb 25, 2012 5:21 pm

Not much happening now as the re-builder didnt give me my rear oil flange,front pulley, timing belt sprocket & key-way [& i didn't remember either!

].
& my old turbo pistons while i think about it...hopefully it will all turn up on Monday!

WideOpenThrottle · Post by **WideOpenThrottle** » Sat Feb 25, 2012 7:09 pm

Hi Keith - so if my maths is right using your figures then my top & middle ring gaps should be no more than 0.375 mm?

So i am still approx 0.0075mm too large a gap by the sounds of it.

Cheers

Gary

Keith Jones · Post by **Keith Jones** » Mon Feb 27, 2012 9:45 am

Wiseco specs are on http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf
It looks like the 2nd ring gap is just about on spec but the 1st ring gap is a bit on the high side.
At least an overly large gap won't cause any engine damage, and I doubt that the excess gap would cause any significant blowby.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon Feb 27, 2012 10:22 am

Thanks Keith....just rang the engine reconditioner who supplied the rings & pistons seems to think the gaps are fine especially for my set-up.

Hope to catch up soon.

Cheers

Gary

Ring gap

Ring gap

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