DCOE Emulsion tube change

[wxneypar]

Hi guys! How are you?
While rebuilding my car for 2021 season I'm looking to fix all the small things that you know are bad but they are not that bad to fix them immediately haha.

One of them is my jetting. My xflow is on twin DCOE's with 32mm chokes, 135 mains, 180 air correctors, F11 tubes.
(For context, 10.7:1 cr, lightened flywheel, electronic ignition, a really nice head on 41/35ish valves and an old iskenderian long duration small lift cam, doing around 125 hp at the fliwheel)

With that setting I get the mixture ideal for me (12.5 to 13 afr) from 6k rpm to the redline at 7.2k.
Great, perfect, but in the lower part of the main circuit, from 3500 rpm to 5500-6 is really really rich, sometimes showing 10 in the afr gauge on the lower section of that rpm band (like at 4k rpm).

So I'm guessing I need a change of emulsion tubes, something that is exactly the same as the f11 at the top part of the RPM range, but leaner from the bottom of the range.

From what I've been reading here, I need to order a set of F9 and start from there.
As I am in Uruguay I want to ask before I order them from the UK so I don't wait a month and get the wrong ones

Does that sound correct? Any other recommendations?
Thanks in advance!

Peter

[trialsrich]

Hi,

With no dyno experience and only ever ‘playing’ with DCOE’s on X-Flow I’d suggest changing the tubes only will not have the result you’re looking for.
I believe (with only limited knowledge) F11 are designed to lean out the mixture at high RPM when compare to F9... changing to F9 might make for rich running at all RPM so then you’re into changing mains...

Hopefully someone more informed will jump in and correct me!

Cheers

[Graham]

im far from expert here, but to my eyes 135 mains are very big given your spec, i would suggest reducing size of mains and airs

[Miniliteman]

Tuning carbs is not easy, some say it is a "black art" as there is no one and definite solution for changing the mixture so that it becomes OK in all rev-ranges and loads.
Like Graham said you could change the main jet to 130 and the airs to 165 to get a leaner mixture at mid-rpm.
This could mean though that the idle jet now becomes too lean so you might need to alter that to one size higher and/or same jet but with different air-hole.
Changing from F11 to F9 would not solve your issue in my experience.

[wxneypar]

Thank you so much guys, I'll go that route.
It's actually good news, cause I can get jets here in Uruguay but I cannot get emulsion tubes!
I'm also building a new engine with the 234 cam so probably was going to need change the jetting anyway.
Thanks again