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Mar 11th, 2023
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I have three different valve springs heights and not sure which to use. I hope the photo shows the sizes. I think the shorter spring is for a 500cc as it has less coils. The inner springs are all the same height
Last edited by Richard Phillips; 11/06/22 12:12 am.
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Or at least check force at valve closed and open dimension.
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From what I can see however, the tall spring is the early spring on heads from 62-65 approx The shop manuals, both early and late thru 1967 show the outer spring height as 2-1/32".
1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
1965 BSA Cyclone Competition Build
1965 BSA Spitfire Hornet Build
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This makes sense because of the big valve head.
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what is more important than free height is spring rate . The middle spring looks just off the pic to be a much heavier wire gauge and the number of turns differs from the springs show
the heavier the wire and the more turns the higher the rick of coil binding
myself i woud do with the longer one which looks to have smaller wire ... all that would differ would be the pre load
what are the wire diameters and number of turns ? ... without knowing this its all speculation
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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A65 1962-67 outer valve spring free lenght 2 1/32"
A65 1968-72 outer valve spring free lenght 1 3/4"
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Interesting.
Wire diameter was the same on all springs. Shorter springs have five coils the other two have six.
I ordered a spring pressure gage to check what I have. I’ll post what I find.
Thanks all
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the strongest will be the one with less turns , funny about picture the middle one sure looks like heavier wire .
when you measure a compression spring rate you preload it a bit first , then measure how many pounds/kg over the same distance of compression ..
there are spring rate calculators online BUT you do need to know the GRADE of wire which you cant know just by looking at it ... all spring wire is not created equal ( but just for comparison doesnt matter)
let us know what you come up with
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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or 
![[Linked Image from live.staticflickr.com]](https://live.staticflickr.com/65535/51431871691_a2afd9ef80_n.jpg)
