Looking for some advice from some of the racing lads, the engine i just took out of my project zxr has blue topped valve spring, i have been told these are an upgraded spring (aftermarket or kwack-gen?) and that originals are white.

The engine has a big hole in a piston due to a dropped valve which i have deduced is down to a snapped retainer that was floating in the head.

are the blue valve springs an upgraded part or from another model of zxr? also would a heavier valve spring cause a retainer to snap/split or would it be down to poor maintenance valve clearance wise.

i regularly service and check clearances and intend to use it on the road and a few trackdays, and wonder would it be worth swapping the springs into the next engine i get? or is it a poor idea to use these for road use?

Thanks in advance
Paul