First post here, thanks for reading! These forums have given tons of insight on how to make better espresso.

Currently stuck deciding whether I should
1) Buy a new grinder, upgrade from Rocky with Teflon tape mod
2) Mod the Silvia v2 to decrease brew pressure, since it's not adjustable out of the box
3) Something else?

The problem: Shots are running too fast.

I use freshly roasted (1-2 week) full city coffee. 15.5g in stock double basket, no screen imprints or obvious signs of channeling in bottomless portafilter. WDT and tamp. Shots start at about 6 seconds, comes out evenly/fast, and only take about 14 seconds for that 1:2 ratio. Grinder is set to true 0, just before burrs touch, and has yet to choke the machine. Burrs were replaced in the last year.

Anyone have any suggestions on how to troubleshoot? Totally willing to upgrade to a better grinder, but I'd be pretty sad to find out the problem is the machine. or even worse, the person behind the portafilter

Thanks for the veteran advice!

Because adding a copper washer to the OPV is the cheapest thing that's easy to un-do, I would try that and see what you think. Of course I don't know what pressure your machine is running or how you're measuring it. A teflon-stepless rocky should be able to adequately control your brew-flow so that the shots aren't running too fast. It may still produce nasty espresso if the pressure is way too high, but dialing in the grinder to find the 30 second shot shouldn't be difficult.

Or just replace the OPV with a new OPV, the adjustable ones fit and will give you the ability to try at many different brew-pressures.
Not quite as inexpensive as the copper washer, but certainly a mod that's worth the cost.

Why not trying to increase grind qty to 17 or 18 gr before making more complicated/expensive steps? 15.5 is small to me. I may be wrong but at least, testing it will cost you only 3 mns and 18 gr of beans

Definetly upgrade your grinder. I used a Rocky for 19 yrs and started getting much better results after changing to a stepless grinder (Ceado E37S).

Thanks all for the swift responses! John had a great point, why not try?

Looks like I was incorrect about my OPV's adjustability. Was tricky to find a wrench thin enough at 20mm to adjust, but I made the changes! Running the pump for 30 seconds now outputs about 130g of water from the overpressure hose (was previously 0g ). I'm told this is a very rough approximation of 9 bars.

The machine is still nowhere near choking with the 0 setting on the Rocky, but flow has definitely decreased in a good way. Pulled another short shot including temp surfing like always, but I think I tamped unevenly because I was excited.

Will give it a try again tomorrow morning and report back!

Thanks for the basket recommendation Craig and the grinder rec Jeff

How old is the Rocky? If it is in regular use and the grinder is more than about 2½ to 3 years old, change the burrs. Then use it for drip and get a grinder more suited for espresso use. You sound committed, so invest in a good grinder that will serve your needs well into the future for when you upgrade your espresso machine. I had a Rocky for about 7½ years and it was ready for its third burr replacement when I sold it.
Read my blog- btdt.

Rocky can usually grind fine enough, I used one for many years. Did it grind fine enough prior to changing to the current burrs ? Is the zero the true zero where the burrs touch, if not re-zero and grind finer.

Recommend cleaning the grinder and re-installing the hopper and re-zero, and up-dose the basket are easy least costly options.