i saw on a thread that the stock a15 can rev 8500 rpm. does is have factory double valve springs or tighter single spings than the a14 or is the cam profile different than the a14?

Not a chance.
The stock A15 have max power at 6000rpm. I bet the stock valve springs can also only handle 6000rpm. It must have been a worked A15 motor.

look at ddgonzal's reply in the a-series newbie thread. he says that a stock a15 short block will rev 8500 rpm

Yes, short block i.e. bottom end, can probably rev to 8500 but you WILL need good springs on the head and the rest of the gear to get it to turn that high.

thanks for clearing that up. cheers

You'd probably also want to add new rod bolts, and arp at that, if you want to play with those sorts of rpms. Often rods themselves can last a long long time, but the bolts themselves (and this isn't specifically a datsun thing by the way)can have a finite life, and the higher the rpm, the shorter that life will be.

We'd also have to add in there that to actually make good power at those sorts of rpms, requires a very well ported head, carefully selected headers (with regard to primary tube diameter, and length and main collector size too) and the sort of carburettion (either a custom plenum and efi, or alternately twin webers/dellortos or efi throttle bodies on an IR manifold. And a pretty serious cam.

And then you'd have to add in that it'd be a pig down in the lower rpm range, have a real thirst for fuel even driven somewhat moderately, etc etc.

So yes, the bottom end is certainly capable of it, but it has to be put in context.