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piston and rings question

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Old Nov 5, 2005 | 04:33 PM
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From: essex
Default piston and rings question

firstly how do you tell the difference between the top and middle ring on a zetec??
secondly if i have brand new 84.5mm oversize pistons and rings then how big does the bore have to be??
if i slide the rings down the bores there is between 1mm and 1.25mm gaps so is this exceptable on a newly bored lump??
my engines a smoker but i cant see anything at all wrong woth it other than it being just all new parts.
i think my ring are not it the right slots though.
please help
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Old Nov 5, 2005 | 04:41 PM
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From: essex
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also where my bores have been bored out its fairly rough, its not mirror smooth like a used lump, is this ok?
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Old Nov 5, 2005 | 09:20 PM
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From: sheffield
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the rings should be a nice tight fit in the bores u shouldn't be able to put them in and out easily with gaps!
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Old Nov 6, 2005 | 07:25 AM
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Originally Posted by HORNETS7
the rings should be a nice tight fit in the bores u shouldn't be able to put them in and out easily with gaps!
no mate rings are supposed to have a gap but i just wondered what was exceptable for a newly bored lump
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Old Nov 6, 2005 | 08:08 AM
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Originally Posted by rs2000mk5
Originally Posted by HORNETS7
the rings should be a nice tight fit in the bores u shouldn't be able to put them in and out easily with gaps!
no mate rings are supposed to have a gap but i just wondered what was exceptable for a newly bored lump
IF THAT WAS THE CASE WHY DO U NEED TO PUT THEM IN WITH A PISTON RING COMPRESSOR?
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Old Nov 6, 2005 | 11:25 AM
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From: essex
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no mate, im sorry but you dont understand.
ring gaps is a common part of engine building.
every engine has ring gaps.
please i only need correct info as i need to get my engine sorted asap.
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Old Nov 6, 2005 | 03:30 PM
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Originally Posted by rs2000mk5
Originally Posted by HORNETS7
the rings should be a nice tight fit in the bores u shouldn't be able to put them in and out easily with gaps!
no mate rings are supposed to have a gap but i just wondered what was exceptable for a newly bored lump
weve got our wires crossed here m8 thought u meant a 1mm gap down the sides of the bores! lol
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Old Nov 6, 2005 | 03:34 PM
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From: sheffield
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did u not notice what prder the rings came out ! sure they arnt the same any how some ore thicker then u have the oil scrapper rings ?

back to your original post the ring gaps have to be offset so all the gaps u mention are on opposite sides!

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Old Nov 6, 2005 | 04:02 PM
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From: south wales
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rs2000,

yes the rings will have a service gap, look in your manual for measurment, also if you have just had your block honed, or rebored
it will a a criss cross sort of pattern this will help the rings bed in,
if you had the work done ask the shop for the ring spec gap,
i recently rebuilt my RS turbo cvh, and asked on picking up the parts
about ring gaps would i need to file them, and was told no, they where
supplied and just needed fitting, i have since run the engine and all good
so check who supplied the parts or measure so far down the bore
and use the spec as in a workshop manual. I have sent you a PM

DAVE R
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Old Nov 6, 2005 | 08:11 PM
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From: essex
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no the problem is the the ring gaps are 1.25mm which is under the 1.4mm ring gap max measuremnt, but its a new engine so once its settled in surely they are going to be 1.5+ causing it to smoke????????????????????????????????????????????? ????????
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Old Nov 6, 2005 | 08:50 PM
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From: south wales
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I would think the ring gaps if under the spec (gap to small)
you have room to alter the spec to what it should be, if the gap was to big
then you would have problems,the thing is if to small the rings can break, this the main reason to check the gap yes as they wear the gap will get
bigger, as all engines wear with mileage if you built it or are building it now, correct them, to within the spec, are the rings new if so ask with your supplier,
( THOUGHT YOU HAD THE OLD RS ENGINE PINTO)
until now, zetec

DAVE R,
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Old Nov 9, 2005 | 03:37 PM
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From: shanghai & somerset
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gap sounds too big.

another thing to make sure of when putting it together is to get them the right way up - should be marked TOP on one face but it isn't always easy to spot on used rings. get them upside down and they totally won't work as they are asymetric.
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Old Nov 10, 2005 | 08:31 AM
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From: essex
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i got it wrong people.
the ring gaps are 0.75mm.
the max allowed in haynes manual is 0.50mm
this is only a tiny bit different so i dont expect it to be casuing too bad problems do you??
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Old Nov 16, 2005 | 03:01 PM
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From: shanghai & somerset
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that's a long way out of spec. the max figure is not really 'alll fine and rosy' but more like 'yes i can still stand up after 10 pints, but not much more'. And if 0.5 is 10 pints, 0.75 would be 15 pints. and that's a reasonable comparison.
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