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I would not run smaller than 130 unless I had a wideband AFR installed that showed nothing leaner than 13.5 at high power. It is very difficult to hear lean detonation at high rpm and there is no upside to that. Webers very often run rich in the mid range and a smaller main jet may fix it and make the car feel better but there is much risk involved if you do it blind.
 

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Ed,
Thanks, I purchased a complete Weber/linkage setup a few years ago to convert my '85 spider. Our fuel pressure is adjusted to 2 psi, seems to work fine, does not appear to run out of fuel. The only jetting change I have made is the idle jets. I actually have an AFR, but way too confusing for this old guy. Does/does not the plug color test work? The last thing I need is burnt valves or worse.
 

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But Mad North-Northwest
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Does/does not the plug color test work?
It's basically like reading chicken entrails, IMO. Also pretty tough to do right. The only way to check main jets is do a WOT run, then mid run cut the engine, coast to a stop, and THEN check your plugs. Otherwise you just end up seeing the mixture at idle.

These days everyone basically uses a portable exhaust sensor: there are 12V powered ones that use a probe in the exhaust. You drive the car and have someone monitor AFM in various conditions.

I suspect but cannot prove that your lean main jet is compensating for the overly rich idle jet (which feeds both the idle jet and the progression holes, so it's basically everything up to when you're on the mains.) If your engine is stock I'd suggest trying the stock 2L Alfa jetting. I can't claim to have tuned a bunch of cars, but both my Alfas with carbs are basically stock, tuned to the book, and drive very well. If you've got significant mods it's likely worth finding someone with an exhaust sensor to tune it.
 

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Sunny and 55 today in Buffalo, NY. Had a chance for a quick run with the spider, found a deserted road and ran her at full throttle for 10 - 15 sec and cut her off. Coasted to a stop and pulled the plugs. Color was close to the color of chocolate milk. From what I know this is a good sign, if not please chime in.
thank you
 

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To follow-up on Malcolm1's post, on my Alfetta with 60F8 idle jets I pulled the plugs yesterday to check them for the soot buildup he mentioned. All four plugs had minor black soot (not oil), easily cleaned with a stiff brush. This was after maybe 1500 miles on these jets. Gas mileage has ranged from about 22 city to 27 steady highway.
 
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