I am fixing up a suspension on a 71 with 85k miles. The car obviously sat around alot. How would I know if the springs were needing replaced? Is there a way to measure the spring rate or should I just replace them? This car will be a summer car and all other pieces of the suspension will be restored stock.

Any suggestions would be appreciated.

Aftermarket springs often mess up the ride height -- several examples in recent posts here and in zcar.com.

"Stock" Nissan replacements will probably still be the 72-73 OEM version. They were wound a little longer than original 70-71 springs to allow for the weight of aftermarket A/C installations, and superceded them in parts stocks. The longer springs make 70-73 Z's ride about 1/2 inch nose up with no A/C, which doesn't look quite right. The slight rake of an A/C equipped 70-71 looked good, it just reduced ground clearance a bit more than Nissan liked.

The rate is probably still OK -- Z springs don't have a history of losing their temper -- so if yours aren't rust damaged you may be better off keeping them.

From your Avatar, I would guess that the car is disassmbled right now. If not, then there are several threads that provide factory ride height measurements, you can find them, as well as loads of other useful info if you do a search on "springs".

If you want to replace them, be warned that OEM springs are NLA for the most part.

Steve, the factory ride height at the bottom of the rocker panels (not the pinch weld) measured at the jack points was supposed to be between 7.75" and 8.0". My '71 with 60k was 8.0" up front and 7.875" at the rear with the original shock. If your car sits similar your springs are probably fine.

But bear in mind that modern gas-charged shocks will increase the height of a car running stock springs a bit - in my experience KYBs added another 1/4" at both ends.