Small block Webers

race-it · #1 (**permalink**) 06-18-2009, 07:20 PM

I have my IDF 44's pretty good but I am still not satisfied with the too rich to often. I went down to 115 Main Jets but looks like I could go down to 110 or 100. I'm concerned that my fuel flow may be to little when I stand on the pedal if I keep going down to correct my too richness.

347 Stroker 425 HP
Main Jet 115
Idle Jet 40
Air Corrector 185

At above 2500 to 3000 it gets lean, Not to bad but lean, as high as 20 for a second or two. I smoothed out my LM-1 numbers so the graph does not jump all over the place. What do you think? Raise Air Corrector to richen at high rpm and lower main jet to lean out at lower rpm?

Now Weber is calling me to buy jets, OUCH!!!!!

eric johnson · #2 (**permalink**) 06-18-2009, 08:10 PM

What size emulsion tubes are you employing?

race-it · #3 (**permalink**) 06-18-2009, 09:37 PM

F-11 Tube. Are you thinking F-2 for a change?

Rick Parker · #4 (**permalink**) 06-19-2009, 12:37 AM

The emulsion tube dictates part throttle action. I suggest you go down on the air correctors in small steps to richen the overall mixture.

race-it · #5 (**permalink**) 06-19-2009, 10:14 AM

Rick, Good to hear from you again. When I went from 175 to 180 to 185 it caused my top end lean problem to become richer. Now it does become confusing when you go to the Air Corrector Jet as to how it effects the air fuel ratio. The larger the air jet number, the leaner the top end mixture. Yes or No? I'm fighting to lean on bottom and too rich on top. To correct bottom end I went down on main Jet as stated to 115 but still to rich. To correct the top end lean problem I went up to 185 and thought I may need to go even to 200. As you well know, Change one thing and everything can change.

Rick Parker · #6 (**permalink**) 06-19-2009, 10:40 AM

There are a lot of ways to achieve the end results but increasing the air corrector size (raising the number) is by design intended to weaken the WOT mixture, and delay when the main system comes on line. The fuel jet/air corrector are going to impose a limit on WOT air fuel ratio. Any time the throttle is not on the floor the emulsion tube is involved heavily and the limits of the jets have not been reached. The small block race cars (with 40 or 42 MM venturis) reduced the air corrector in an effort to bring the main system on line quicker (exiting turns) with foot on floor and to richen the WOT mixture.
All things being equal, the use of a moderately agressive [b]Roller cam[b] cam on a given combination will allow the use of a smaller main jet because of a more abrupt pressure drop in the venturi during valve opening.

race-it · #7 (**permalink**) 06-19-2009, 10:55 AM

OK, I will go down from 115 to 110 to 100 and maby I can make my low end 2300 RPM to 2800 RPM AFM leaner to stay around 12.5 . Now you have me spoiled and to settle for less than perfection is unacceptable!!!!!!!
Thanks Alot

Another question: I smoothed out my LM-1 to take readings every 4 seconds instead of every second. Is that to long?

Zoom This · #8 (**permalink**) 06-26-2009, 08:51 AM

You have a PM from me.

Bill