Noob question.

why double valve springs, is it just to get the compression rating higher, eg a 140 plus a 60 gives 200)- but still meets the minimum pressure specs

doesn't it present more options for binding than a single,,, or is it just horses for courses ?

Having an inner spring touching inside the outer spring damps down vibration harmonics which coil springs go through.
It also allows lighter wire to be used in the outer spring.

Singles were generally used for up to 5500-6000rpm on standard A series, with doubles used above that (Cooper, Cooper S & Clubby GT).

If running a hi-lift cam and or 1.5 rockers it's recommended to use springs suitable for the extra lift. eg Minispares C-AEA526 or 527. Where using stock springs would give coil bind.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

thanks, makes good sense