Something else has just bubbled to the surface of what I laughingly call my brain...
I think I'm right in saying the head bolts are designed to shrink slightly then work-harden once installed and run for the first time, so you need to replace the bolts with new or you'll never get the extra bit of tightness that comes from the bolts shrinking, so your nice new gasket won't last as long as it should...
Just how difficult is a head gasket?
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KevR
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mat_fenwick
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You might be getting mixed up with stretch bolts, used on the XUD engines (I think!) after '86, where you torque the bolts until they stretch. The way I understand it with stretch bolts is that you get a much more uniform clamping force - as once you have made the bolt material start to stretch then you can't apply any more force. So assuming the bolts are all heat treated correctly and consistantly, you should have an equal force on all of them, without the torque figure being skewed by more friction on one bolt than another.
Plus, as Doc has previously pointed out, as the head expands more than the block the stetch bolts keep the clamping force more constant over each heating/cooling cycle.
You can (and I have done once previously) re-use stretch bolts so long as they haven't been stretched past their maximum length but I would recommend changing them, for piece of mind if nothing else!
Plus, as Doc has previously pointed out, as the head expands more than the block the stetch bolts keep the clamping force more constant over each heating/cooling cycle.
You can (and I have done once previously) re-use stretch bolts so long as they haven't been stretched past their maximum length but I would recommend changing them, for piece of mind if nothing else!
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KevR
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Ah, that makes sense. Thanks for the clarification.
1990 BX TZD Estate ('the grey one', 1991 BX TZD Estate ('the white one'), 1982 2CV6 Charleston (in bits), 1972 AZU Serie B (2CV van), 1974 HY72 Camper, 1990 Land Rover 110 diesel LWB, 1957 Mobylette AV76, 1992 Ducati 400SS, 1966 VW Beetle, 1990 Mazda MX-5, 1996 Peugeot 106D, 1974 JCB 2D MkII, 1997 BMW R1100RS, 1987 Suzuki GSX-R1100, 1978 Honda CX500A, 1965 Motobecane Cady, 1988 Honda Bros/Africa Twin, 1963 Massey Ferguson 825, and a lot of bicycles!