F-2's, F-11's, and F-7's, Added F-4's too.

[DKK Ted]

Ok, what is the bottom line on these, especially the F-2's?? Oh! And the F-8's???

Ted  

[ibg]

Ted, here is my gathered wisdom from Weber, Passini, John Connelly, JMP, Art, and Bergs who all know a lot more about Webers than me
my 2387 86B with 42 vents likes F2's, I tried a lot of others.

F11 tube you want around a 200-220 air most of the time (main  + 60). Some top end richness, but leaner everywhere compared to F7 Good for Venturi up to 37
*** Slight leaning of mixture at low RPMs and during acceleration. Used to lean out high RPMs when you have an air jet larger than 200. We recommend the F11 for 95% of dual carb applications, it's an excellent all around emulsion tube. John C

F2 (richer midrange then F11; slope is flatter then F11)
Weakens at high rpm, thin (good for big mains) PASSINI
Rich part throttle? Smaller air than F11. Rich top end ART.
***F2This tube has a slightly richer low end and acceleration then the F11. We recommend the F2 with 40mm or larger venturis. John C
Fatter than F7 down low, likes small air eg 160M / 160A – BERG.
For 40 or bigger venturi (also F8)

F15 like F11 but later tip in *** with a slightly richer mid-range.

F7, early tip in. ‘At low and midrange the A/F is too fat that is why there are small bumps around 4-5k rpm, maybe with F-16 or F-9 E-tubes I can get rid of those’. JMP The F-7 E-tube is a very fat tube at low and mid range. F8 bit leaner, large airs needed. PASSINI
*** F7  Very common emulsion tube in VWs for race use, which is a joke because WE ONLY RECOMMEND THIS TUBE FOR CENTERMOUNT CARB APPLICATIONS, or Big Block V-8s with 1bbl/cyl. Richens at low RPMs and slightly during accelleration. This is a horrible emulsion tube for 1bbl/cyl VW engines. John C

[Jim Ratto]

Ted you can kind of eyeball an emulsion tube and 'see' what it's going to do. I read a very article on taking the hype and black magic out of e tubes on a Ford Cosworth site and David Vizard has a great short thing on Youtube.
Anyway, not being one to take the internet as the end all answer, I tried what I read against my own car and my NTK broad band sensor and it made sense to me.
I have tried F7 and F11 and both came up short in several of the engines in my car, a far as power coming in smooth, crisp and early. The F11 were the worst.
I currently have F4's in my 48's with 40mm vents. I switched from F2's.
A high (13.2:1) CR 2276 I did last year, with 288 @ .050 cam has F2's in it, replacing the F7's that were in it.

I'd like to try a set of F16 in a small cc high rpm motor with 48IDAs some time.

[Jim Ratto]

Ted I can email pictures of differences in amount of holes and location of holes in F2 F4 F20 and F11 if you want. I can scan my Weber book too if it will help. Let me know. Have Fun
Jim

[benlawrence]

I ran a couple of dyno pulls last week on my f7's, 2276 with wedgies 10.5 comp 86c, 37mm vent,  just wanted a base to start from, 2 prog holes.

4.5-6k rpm, 160 main 200 air, fuel good, below those rpm extremely rich on wot, but we knew that right    I'll chime in with some other numbers with f11's and possibly f2's once im ready to go back to the rollers.  

[DKK Ted]

Ted I can email pictures of differences in amount of holes and location of holes in F2 F4 F20 and F11 if you want. I can scan my Weber book too if it will help. Let me know. Have Fun
Jim

PM sent.

Ted

[neil68]

Bought some Jaycee prepped IDA's with 42 vents and F7's.  Switched to F2's and lost a couple tenths in the quarter mile...

[DKK Ted]

Hey Jim, I have a set of F4's etubes. What would be the jetting ball park to start with? My jetting now is, 160 idles with 115 holders, 200 airs on F7's with 160 mains. Thanks Jim.

Ted