Gaggia Classic (adjusting the OPV)

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Over Pressure Valve

While researching into my own machine (Rancilio) I came across an interesting mod that is done to the Gaggia Classic, according to the link below all Classics are set at 14 bar for coffee pod rather than naked grind use, as 9 bar is around the optimum setting I thought this link would be useful to new Classic owners.

http://coffeeforums.co.uk/showthread.php?3859-Adjusting-the-OPV-%28over-Pressure-Valve%29-Gaggia-Classic

If you want to make yourself a pressure gauge I bought my gauge from these folks

http://www.ebay.co.uk/itm/Pressure-Gauge-air-oil-water-60mm-0-150-PSI-0-10-Kg-cm2-Bar-1-4-BSPT-/130624550050?pt=LH_DefaultDomain_3&hash=item1e69d474a2

the links to the actual fittings are below + PTFE tape

Please check thread dimensions on your own portafilter, if you're happy with results ignore.
 
now I may be wrong(does no happen often though)

but the portafilter threads are 3/8 and the pressure gauge is 1/4 so would be one of these
http://www.ebay.co.uk/itm/3-8-BSP-316-STAINLESS-STEEL-ELBOW-90-DEGREE-150LB-/220565167817?pt=UK_DIY_Materials_Plumbing_MJ&hash=item335ab55ec9#ht_500wt_922

and one of these
http://www.ebay.co.uk/itm/3-8-X-1-4-BSPT-HEX-REDUCING-BUSH-316-STAINLESS-STEEL-/220594588050?pt=UK_DIY_Materials_Plumbing_MJ&hash=item335c764992#ht_500wt_922

with the pressure gauge to make it all fit.

But cheers for the link have a pressure gauge here to do this and was putting off looking for the fittings but this seller is spot on.
 
Thanks for the clarification, I thought I'd read the Classic filter had 1/4 thread but as I don't have one I wasn't sure.
 
Cheers antdad for finally making me move my arse and do this, I have now set my pressure at the required setting( You put doubt in my head to the size so ended up going into somewhere today with the portafilter and checking the size so got the parts from there)

all setup
d0ba6121.jpg


I had a problem with water coming out the top of portafilter even though I had the basket in but was easily sorted with some PTFE tape round the outside of the basket to make it a real snug fit.
( just noticed should not have had the basket in, that would have solved the leak problem, just re-tested still the same reading so no biggie)
these are cheap as chips to make I got the bends from BSS or something similar and they even do pressure gauges(wish I had knew that earlier) but if anyone wants to borrow this I will post it round. should fit all machines or so I was told most portafilters are 3/8 thread.
 
Ah good, my bits came through today but I need one because of a new pump installation. Seems little point refining everything else if the group head pressure is way off, was your pressure high as the article suggested it would be?


BTW: Not forgetting your measuring static pressure rather than dynamic, add 1 bar to what is desired.
 
Following this with interest fellas, blew all me pocket money on an iPad this month so next month this will be my first mod when I get my Classic.

Let us know your results and Pedro hang onto your gauge, I will borrow it if you still have it when I get mine.

Cheers
 
Heck I'm getting out of my depth here....
I'm interested to know how much difference this makes. I'm interested too in having my machine tested...
Does this mean taking the spout off the PF?
Mine is stuck stuck stuck.
Great post and the link is excellent.
Tim
 
It should improve crema formation and the general flavour quality of your shot, I'm getting sensational crema now I've adjusted mine.

9 bar seems to be the optimium setting and yours is I assume like Pedros set at 14 bar, I guess because it's so high you are compensating for under extraction by wanting to grind finer and tamp harder.
 
Well,
it sounds a bit dumb but I only know what I know. I have no comparisons.
I get the Guinness effect in a shot glass. I get good crema. The shots taste fine (too me!)
I need to tamp not very hard with the single basket and harder but really really hard with the double.
2 ozs with the double takes about 25-30 secs.
Si I'm stuck a bit on improvements for a bit because of my lack of technical expertise over the machine and valves and such and what good coffee is like for other people.
We need a shaving/coffee/bread GTG!!
Kindest
Tim.
 
It's really up to you, you've now honed your technique to suit your equipment setup.

Crema colour is a good indication of under or over extraction.

Underextraction
underextract.jpg


Overextraction - burnt appearance
overextract.jpg


Caramel colour and particles showing good extraction
tigerflecking.jpg
 
Ok this helps. More like pic 1.
Not like pic 2
Some elements of pic three.
How do get a better extraction?
Finer grind. Hope not ill have to sell a razor or two!
Tamp a bit harder?
Great and helpful pics.
Cheers
Tim
 
Slick said:
Heck I'm getting out of my depth here....
I'm interested to know how much difference this makes. I'm interested too in having my machine tested...
Does this mean taking the spout off the PF?
Mine is stuck stuck stuck.
Great post and the link is excellent.
Tim

My spouts were the same I put a cheap screwdriver type thing you always get with machines or flat pack and the such through the hole( had to try a few till I got a good fit) then gave a nice hard twist, and I mean hard, it then loosened and eventually came off. They must put thread lock stuff on these in the factory but they are normal direction threads and do come off.
 
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