Found some Bilstein inserts.

[jmortensen]

Insomnia is a bitch. Just found a calculator and did some estimating: http://www.pontiacracing.net/js_coil_spring_rate.htm

If you plug in .455 for the wire diameter and 10 coils and an outside spring diameter of 4.625, you get a spring rate of 83.12, which is pretty close to stock. I found a picture of a stock spring, and it looked like it had 10 coils. Remove one coil, spring rate goes up to 92 lbs, which is ~11%. Cut two coils, it goes to 103, which is 24%. It may be that Dan just cut 1/2 coil. Regardless, 103 in/lb is still a really lightweight spring.

Looking at Arne's example, if the Euro was 15% stiffer than stock, that would make it about 95 lbs. Adjust the spring wire diameter to .47 and that gets you in the ball park, and then cut a coil and a half (guess), and you get 112 lbs, a change of 19%, but still, a very light spring.

[AZ-240z]

I bought a Seires 1 parts car a while back and found a NOS set of factory inserts in the boxes. Does anyone know how well these performed? jlp

Jerry,

Sorry that I didn't notice your question earlier. Nice find on the factory inserts. It has been 40 years so I can't be very specific, but I would agree that the ride and performance was probably most comparable to the KYB inserts as I remember. I do remember having a set of Konis installed some years later and noticing a markedly firmer ride with less body sway. I currently have a set of Mulhollands paired with repro springs offered at Courtesy a few year back. One of the Mulhollands, after probably some 30+ years on the shelf, is binding and the ride is way too firm so I am considering another set of Konis. I would do KYB-GR2 inserts but don't want to chance an increase in ride height above stock with the gas insert, and don't want to cut my repro springs.

Let me know what you end up doing with yours. Are they going on your red car being done at Classic Datsun?

Dan