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Lister JP valve springs - when to replace?


RAP

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I would replace if they are broken otherwise not worry unless you have specific cause. They are not a regular service item, to this end no specific mention is made of them in the workshop manual. For sticking valves it just mentions cleaning valve stems and guides for example.

 

I suppose if you were contemplating a complete engine overhaul including new valves, guides etc. they might be worth replacing.

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Hello,

Does anyone know the specs to help me determine if the valve springs have weakened or is there a simpler 'engineers' method to measure this?

Thanks.

The traditional method is to put a new one next to the old one with no load and compare the heights. If the old one is shorter by more than about 10% it is time to replace.

 

Also replace if the is any sign of rust. Not usually a JP problem if regularly used.

 

N

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  • 2 weeks later...

I decided to purchase new inner and outer valve springs. Good job I did, you can see the comparison between old and new in the attached videos.

 

 

https://youtu.be/ulsDuHuzQKs

 

https://youtu.be/K6bmyw1-8QM

 

 

 

They look very different springing rates. Have you measured and compared the diameter of wire?

 

I would expect a tired spring to be shorter, but not have a lesser springing rate.

 

BICBW

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