Has anyone tried to add a small spacer to a Zacconi spring lever machine... to create a bit more tension in the pull? would this work? I'm thinking 10mm

To work out the thickness of the spacer that you can fit, you need to know.
1. the length of the spring when the lever is fully down.
2. the length of the spring when it is fully compressed (when all the coils are touching each other).
3. the maximum height of the spacer that will fit is the difference between 1 & 2.

I am not convinced that increasing spring preload and thus pressure is the path to a "god shot". At the moment I am using the same beans with the same water in an Expobar Office Control HX, Microcimbali and Cappuccino Amore CE14. I am getting great results (but different) from all machines and the working pressures would be very different. The Expobar is pumped so will be up at approximately 9bar, and the CE14 is probably closer to 5bar. With these beans I personally prefer the results from the CE14 at 5 bar!!!

This old thread might help: Spring on my Riviera might be too weak?

shotsonyachts wrote:Has anyone tried to add a small spacer to a Zacconi spring lever machine... to create a bit more tension in the pull? would this work? I'm thinking 10mm

What vintage Zacconi? I had written down a lot of measurements and notes on the spring of my early Riviera, but I think I dumped them recently. I did replace the old spring in mine with a new Ponte Vecchio D.37mm H 80mm M7070 spring. It made a huge difference for crema anyway. I had put in the PV spring but took it out as it didn't let the piston up fully as before. The inlet hole was about half covered. Then I put back the old spring with a makeshift spacer of very hard rubber. (it got compressed, so use metal of some sort.) Then decided if I ground down the PV spring a bit I could try it again. I'm pretty sure I ground off 2mm. Given the number of rings on the PV spring at 5mm wire diameter over the old spring at 4 mm and about 7 or 8 turns, one can guestimate the extra room the old spring had when compressed with the piston up. Probably about 6 mm. I'm pretty sure a 10mm spacer will not work. I would try 5mm maybe 6 max.

I think the spring rate on the old 4mm spring is about 60 lb/in and the new spring at 5mm closer to 130lb/in. Honestly I can't remember the details well. Good luck.

https://www.acxesspring.com/compression ... tions.html

You might try adding a spring inside the original. I had found some I thought could work, but didn't go that route as I already had the PV 5mm spring. I think I remember two springs situated like that the spring rate is added together.