Weber jetting question

[udidwht]

Currently running dual 40mm Webers on 2056cc Type4 (72 Westy hard top)

50 idles (mixture screws are at 1.25 turns from seated position)
120 mains
F11 tubes
200 airs
not sure of the venturi size either 28mm or 30mm

Van idles real nice and sounds very crisp to throttle response I'm just a bit concerned that it might be a bit lean on the top end. Was thinking of stepping up to 125 on the mains. Is it just a matter of pulling the 120's and replacing them with the 125's? Or are there any other adjustments to be made, such as mixture screws etc...

Recently made a trip and my mileage was 22 mpg roughly @ 60mph with the current carb jets, 16 mpg around town.

Type 4 2056cc

96mm P/C's
42x36mm heads
71mm stroke
#73 Web cam w/ matched solid lifters
Dual 40mm webers
009 dizzy w/Pertronix
S&S 4in1 header w/quiet pack

[500LbGorilla]

I am using 125s in my 36's with 28 vents. The air jet could stand to be about 170 on your setup, I'd bet.

[udidwht]

Air corrector jet 170. Is that more air or less for the main? So 120 sounds about right? Just change the air corrector? Or both?

[Piledriver]

Air corrector jet 170. Is that more air or less for the main? So 120 sounds about right? Just change the air corrector? Or both?

Air corrector will have a small effect at low end, mostly effects top end.
Change one thing at a time. Sounds like you're almost perfect.

[udidwht]

Which should I try first given what I'm running now? Air correctors or the main jets

After switching out either the airs/mains what should I be feeling/expect to be sure it's running top?

Any futher adjustments necessary after changes?

[Piledriver]

I'd personally try just the airs since all else seems right.

Rent/borrow a WBO2 setup. It's the only way to be sure.

[500LbGorilla]

udidwht, you said it felt wrong up top, and by up top, I think of like 4000 RPMs and up. If this is the case, air jets yes.

Smaller air jets means that less air is sucked in to the emulsion tubes at higher rpms, and a little more fuel is sucked in. This will richen the mixture up top. With a bus, my opinion is that you are better off erring on slightly rich than slightly lean.

[Piledriver]

500lbGorilla, your avatar is having a Microsoft Moment?

[500LbGorilla]

You could say a lot of things apply there.. I like to use it as a visual expression when people ask really silly questions, and you are trying to express your attempt to answer that question under duress of trying to make sense to said silly inquirer.

No underlying meaning intended. I've just run across some doozies lately. A guy asking about timing and trying to narrow his advance band because he noticed that pulling his advance up at idle sped the idle up and apparently meant he was getting more power at idle seemed like a good reason to do it is the best one I've seen so far.

[udidwht]

You mentioned going to 170 on the airs. I believe I have 200 in there now, seems like a big jump from 200 - 170. I saw on the Weber site that they come in increments of five 200, 195, 190, 185, etc.

I know I'm close, but like you said I'd feel better on erring on the richer side. What air would you recommend and after installing them what would I be feeling for when driving the van such as sluggishness, responsiveness,etc... to know they're right or not.

[500LbGorilla]

Well, for every jet size, i.e. a difference you can FEEL, about three air sizes is about the same difference, on the top end. You are metering AIR, not fuel with those. You should be about 50-60 higher than your mains with your airs in the range we use these carbs, with F11 tubes.