Mud-club
Vehicle & Technical => Defender => Topic started by: trickydicky on December 22, 2008, 19:23:59
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the engine on my 90 has very low compression and 2 cracked pistons do i use the next size pistons up or will standerd ones do it.i think the next size up are half a millimeter bigger and the piston chambers do have ridges around the top
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For what it will cost you rebuilding the engine you might be better off buying an old Disco and do a 200 TDI upgrade! :D
Rich
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DO NOT fit oversize pistons to a standard bore, it will sieze up solid after about 5 minutes running. The ridge at the top is caused by the top compression ring gradually wearing the bore over time,( tens of thousands miles). To check it correctly the bore needs to be checked for ovality and taper using a precision bore dial gauge...can be too expensive for the average home mechanic.
However you can use a standard compression ring pushed down a little at a time and checking the end gap using feelers to give you a rough idea of the condition, using the piston to push the ring down keeping it square in the bore, you won't be able to check for ovality using this method - only taper
The ridge can be removed using a metal scraper and careful use of fine emery paper, fit standard pistons and rings making sure the end gap of the rings is within spec, and don't forget to deglaze the bore.
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sounds like good advise standerd pistons it is then the only reason im not changing to a 200 tdi is i live in a house whith no drive so i can only work on it in a comunal carpark so i am limited to what i can do. thanks for the replys good answer