quick question.

double valve springs out of a 250 crossflow ford fit into a a15?

yes i found the wonderful world that is the car wrecker

I doubt it. I heard that Mini A-series valve springs fit Nissan A-series.

The ford springs fit the L series heads as i have used them in the past

red motor springs fit,
why would you when GX springs or race 10k ones are cheap..???

aww sweet.

thank you dundee!

VW beetle outers with GMH 6 cyl inners is what i've been told & i've used VW Beetle as a single spring, but twin valve spring sets are available for the A Series, you should be able to get them from most parts places, or a Repco should have them in one of the books under the counter.

will there be any damage caused if the valve spring is really hard ?

Yes.
It imposes additional loads on all of the valve train components & accelerates wear. If your engine is running up near 8,000 rpm & more a lot of the time [like a race engine] then this must be accepted as part of the price of going fast.
For street use where you hardly ever see more than 6,500rpm, then all you get is reduced performance [it takes power to overcome the resistance of strong springs] & reduced component life.

I reckon there will be more wear & tear on the cams...and perhaps the pushrods...am i right?

By the way, did anyone try measuring the spring's stiffness constant ( k )? Do all the A series which comes with single valve spring have the same spring constant?

& crank sprocket & timing chain & camshaft sprocket & tappets & rockers & rocker shaft.

They won't cut service life in half, but the total time in service would be reduced a little.