I'm doing a complete restoration on 73 240Z.  Like most I'm having spring issues.  I'm trying to keep it pretty much stock regarding ride height and performance.  I found a place that can make springs that duplicate OEM but the cost is $600 for a set of four.  More than I'm willing to pay for springs.  Found another place that claims exact stock replacement but 30% stiffer.  I have nothing to compare that to and I do not want a stiff ride.  So I'm wondering.... How do I know the original ones need replaced.  I was planning on replacing them just as a good practice on a restoration.  Seeing how I can't find what I want (or am willing to pay) How bad off would I be if I just reused the original springs.  There are no visible signs of damage. Other alternatives???  I got to believe some other car somewhere has springs pretty close to the OEM  Z ones.

My '71 240z  had the orig. US type 240z springs in the rear and were very soft... i replaced them with euro 240z rear springs and can now load 150kg ( about 330lbs) without the exhaust on the ground!  

The wire thickness of the euro version is thicker.. they are also a bit stiffer.

Also know that the front springs are different!  One is stiffer than the other for as far i heard..  600 dollar for a new set is reasonable i think... Look if they have different stifness in the front ones! then you know if they are really the right ones..  (Look in the serv.manual if a '73 240z has different stifness springs in the front!)

SO... I looked it up for yah...

The wire diam front is both 10,6 and coil diam. is 100mm coil turns 10 and coil eff turns is 8,5

spring constant is 1,48kg/mm (for both sides)

now:  !!

Free length left is 373,5 mm (22.72 inch) and right hand side is 386mm (23.56 inch) !!    (where would we be without a service manual hey???) 

So there is a big diff between length of R and L front springs..

 

Looked also for you on the rear springs, they are the same (L & R) and have:

wire diam 11,4mm

coil diam. 100mm

10,65 windings

free hight of spring is 381mm  and installed 225 mm

spring constant 1,85kg/mm

this came from my (euro/US?) 1971 serv. manual.   i often wonder if we have different service manuals.. i do have the mm and inches in it also Kgm and ft-lbs ...  so it's for euro and american service-men? ...

BTW.. in the early '90's  i looked at a fiches machine a the Nissandealer and had 4-5  different springs to choose from..   Dutch were different from Frence ones and American springs were softer and again... different..

There are a lot of threads around springs maybe read those first before you buy something..

Edited November 12, 20213 yr by dutchzcarguy
changed the word topic in threads!!

If you still find them, Chevette springs can be cut to height. For some reason, there aren't a lot of choices available for a 40+ year old econobox. They give a much firmer ride, but I don't find them harsh or too stiff.  The nice thing is that you can get 2 pairs of springs from Rockauto for $88 plus tax & shipping. The flip side is that you have to be willing to experiment to cut the springs the to right height. 

From re-reading the thread linked below, I guess I was aggressive with the amount I cut, but I'm happy with the results. I cut 3 from the rears and 2.75 from the fronts.

 

Testing your springs.  Per my previous post, I'm in the process of a resto on a 73 Z.  Currently working on the front suspension, replacing / rebuilding everything that I can.  I wanted to change the springs but found limited options.  Chevelle springs seemed the most viable option but entailed a lot of "trial and error" work.  And, as you know, each time you put them on and take them off it's a real PIA. Especially since the car is on a rotisserie and completely disassembled.  I wouldn't be able to get any real information until the engine, doors, hood, hatch ,etc were back on and the full weight of the car was on the springs. So, I decided to test the existing springs to see if they even needed replaced.  Years ago,when I worked as an auto mechanic, rarely did we need to replace springs unless they were cracked or broken. So here is what I did:   

Needed :  A hydraulic press, a bathroom scale (an old analog spring style, not an electronic digital), a yard stick, a piece of stiff wire (welding rod or coat hanger), some short pieces of flat bar for steel shims, couple pieces of wood" and a ratchet strap (optional, for safety).  

Set Up:  Cut a piece of 3/4" plywood a little bigger than your scale and set it on your press.  Set your scale on the plywood

Set your spring on the scale.  Because of the way the spring is cut, it will not set level on the scale. Place the metal shims between the spring and the scale until it sets level.

Use the top spring cover from your strut and place it on the top of the spring.

Fasten the yardstick to the press vertically alongside the spring

Use the stiff wire to create a pointer and attach it to the spring (I used magnets to hold it in place, but duct tape will work too).  Be sure to make the pointer long enough to reach the yardstick

Place a small block of wood on the top spring cover and lower the press ram just enough to hold everything in place.

If you prefer, wrap a rachet strap around the press to catch the spring should it decided to kick out (optional)

The Test: Before proceeding record the reading on the scale (or adjust it to zero if possible).

Also record where the spring pointer is pointing on the yardstick

Check the spring specification in the service manual.  I was working on the front springs and the rating was 83 pounds / inch

Wear safety glasses (just in case)

Slowly operate the press watching the spring pointer against the yardstick.  Continue to operate until the pointer has moved one inch from the starting point. Then stop.

Record the reading on the scale. Subtract your starting scale reading from your finish reading.  This will be your rating per inch.

In my case the reading was 92 pounds.  Since spec is 83.  I figured I'm good.  A little red spray paint, and the look great.  Saved a lot of time and money.  Hopefully the rears will be good too.

BTW:  Be sure to mark left and right springs when you take them off, they are different lengths.  The ratings are the same on both sides.

Thats a cool technique!

I would be interested to hear from anyone that has used the Springs that are 30% stiffer. Z Car Source sells them. I have been finished with my car for about 1.5 years now and every time I throw it in a left hand turn my rear passenger tire scrubs. For all I know I have the wrong springs front and rear. I remember getting some conflicting info when I was putting that all back together. 

I can live with a firm ride, just don't want it to feel like a horse and buggy.

You could bring it down to my place for me to look at.

20 hours ago, SteveJ said:

You could bring it down to my place for me to look at.

I appreciate that. I checked and I have the thicker springs in the rear. May just be a dead spring, its the side the gas tank weight is on. I think I will give the ones from Z car Source a shot and report back. 

I can show you the tricks for changing out springs, too, if you don't know them already.

I wrote the above procedure for testing spring tensions a few months ago.  I finally got around to taking a few pics of the set up in case the written procedure wasn't clear.

Clay...Did you ever swap springs...? I bought Z Source springs and my car sits really high. I'm about to get it back on the road after a 4 year restoration, so I thought I would see if it "settles" any. Any thoughts from your experience...? Steve...? ValpoZ...? Ryals in Ellijay

Edited April 9, 20231 yr by Tirnipgreen
Wanted to include ValpoZ

16 hours ago, Tirnipgreen said:

Clay...Did you ever swap springs...? I bought Z Source springs and my car sits really high. I'm about to get it back on the road after a 4 year restoration, so I thought I would see if it "settles" any. Any thoughts from your experience...? Steve...? ValpoZ...? Ryals in Ellijay

Are you sure you bought the 240Z springs? Are you accounting for sag in the old springs?