I found some sunny oil filled shocks that should fit the larger strut size. Why were people so quick to get rid of these in favor of gas filled ones?
Is it that the valving is crap on compression and rebound or you can't get seals for them anymore?
All good shocks (Bilstein, Koni) use oil.

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Those are strut pieces, guts. There were replaced by insert cartridges starting in the 1970s, meaning that they were no longer rebuildable

Quality cartridges are available in oil or gas-over-oil

To be clear, they are both oil-based shocks:

* Oil strut insert cartridges
* Gas-charged oil strut insert cartridges


The gas-charged type are pressurized with nitrogen gas. This has consequences:
* On bad road surfaces, like washboard dirt roads, extreme vibrations can cause the oil to mix with the air and so lose the shock characteristics. The gas pressure prevent this from happening. This was not an issue on most highways or town roads
* The pressure raises the car up, as much as 10-15 mm
* It makes the shocks stiffer. Being as the 1200 is already stiff, this is not a good thing. Stock 1200 oil shocks & struts don't allow the wheels to skitter & bounce. But once you put gas shocks on they will

Gas-charged shocks & struts became the norm becuase most cars (think old GM & Ford cars) were too softly sprung and as the suspension wore they got even worse. Consumers liked the stiffer gas shocks on these vehicles. New vehicles are designed for gas-charged shocks so they work well

Yes, original oil shocks are very good, specifically tuned to the car they came from. Aftermarket insert cartridges are generic for many cars. So for street use with stock or close to stock suspension, oil shocks are the way to go.

For heavily modded suspension, for example, heavy wheel & tires, a different shock may be better.

The good news is that original Datsun shocks can be rebuilt (as long as someone didn't previously throw the guts away and fit insert cartidges). To renew the front shocks, remove the big nut, drain the oil out then put new oil in. Most repair manuals show how is to do it. Use strut oil (10 weight non-detergent oil) for stock characteristics. 15 weight oil for stiffer damping. Use the exact amount called for by the repair manual (for B110 struts it is 280cc for AMPCO struts; 265cc for Tokico struts)

As long as the o-ring seals aren't dried-out or cracked, no rebuild kit is needed. They can be reused many times

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Very interesting thanks. It's good to hear the older technology of oil shocks is still worthwhile and more environmentally friendly as they can be rebuilt.
Improving performance on dirt and corrugations would be nice. particularly the back end of the coupe which is just too stiff with leafs and gas shocks. I seem to remember the original 1200 rear shocks were also oil and quite small but probably just fine under a light chassis.