Tuning 40 DCOE Weber 151 on an L24

[LeonV]

You may want to try out a 190 air corrector to see if it counteracts the richening trend at the higher revs.

The air corrector should not be used to correct upper rpm mixture, that is primarily the main jet's job. Enlarging the air corrector will affect the transition to the mains (larger AC makes mains come in later, increased potential for flat spot). The AFR curve at WOT is controlled by the emulsion tube/main choke combo. The "right" combo will yield a flat curve.

[Zedyone_kenobi]

I think the main culprit of it richening is the 30mm chokes. I am going to invest in some 32mm to see how they feel. I mentioned above about getting some of the Keith Franck E tubes, but for the money I think 32mm chokes are a better investment. The F11 Etube just seems to be a great fit to Lseries engines.

[cygnusx1]

Without swapping emulsion tubes, and no flat spots apparent in your setup, the air corrector can take out some high-rev fuel. Not correct, but it works to some extent. I went from 28 to 32 mm chokes in my 151's. It's worth doing. I didn't also change the aux venturis to be "by the book" but it runs fine.

Edited August 28, 2012 by cygnusx1

[Zedyone_kenobi]

Can I change out the venturies with the carbs still on the car? It looks like they just pull out.

[cygnusx1]

Yes, with the vel. stacks off, they should slide out with little effort.

Edited August 28, 2012 by cygnusx1

[conedodger]

Perhaps I can add to the body of knowledge being assembled here. I am in Reno Nevada at 4500ft above sea-level. Ambient in August is a balmy 90+ degrees with 20% humidity. I was running extremely rich this spring when I got her running. (I just moved here). The following was my set up:

Idle jet 50F9

E-tube F11

Main jet 145

Air correction 170

Fuel pressure 2psi at idle

Brass floats set to 5.5

Mixture screws were 2 turns out

It ran pretty well with this set-up. But I do have an Innovate LM set up installed in the original ashtray so I can hide it when I want. I would start up and idle at 9.5:1 and pretty much never got much better than 13:1. I made the following changes and took it for a little cruise in the night air just a bit ago. It feels better but I imagine I will need to do some daytime testing and let her get warmed up to tell for sure.

Idle jet 50F8

E-tube F11 (stayed the same)

Main jet 140

Air correction 180

Fuel pressure 2psi at idle (stayed the same)

Brass floats set to 8

Mixture screws 1.5 turns out

[Zedyone_kenobi]

Very nice install!

That 50F8 idle jet should really lean you out ! It was almost 2 points leaner than my 55F9 jets

[conedodger]

I should mention, my carbs are 42 DCOE 8 triples not 40's. After a little drive this morning I find that I have developed a flat spot on tip in, especially aggressive tip in. But, my A:F numbers are much improved. It idles in the 11:1 range and except for when I drop the throttle, it stays in the 12 and 13:1 range. Drop throttle gets you 15:1 and there about... I have found some throttle response and power that wasn't there before which is really nice. Now, how to deal with the flat spot?

Thanks for the props on the install.

Edited August 28, 2012 by conedodger

[240260280z]

I should mention, my carbs are 42 DCOE 8 triples not 40's. After a little drive this morning I find that I have developed a flat spot on tip in, especially aggressive tip in. But, my A:F numbers are much improved. It idles in the 11:1 range and except for when I drop the throttle, it stays in the 12 and 13:1 range. Drop throttle gets you 15:1 and there about... I have found some throttle response and power that wasn't there before which is really nice. Now, how to deal with the flat spot?

Thanks for the props on the install.

For flat spot:

1. Set fuel surface from the top of the casting ledge of the main jet well.

2. Play with bleed back hole size and accel pump length if you lean-out on punching it. (Old racers say to "squeeze" the pedal rather than punch it...I am thinking they ran Webers that were not transitioning well.)

[Zedyone_kenobi]

I would also go down one size on your air corrector. It may help with the flat spot.

well it worked for me!

[conedodger]

I would also go down one size on your air corrector. It may help with the flat spot.

well it worked for me!

I just ordered the Franck fuel level tool. I will set my fuel level with that first. I believe he says 25mm is ideal? I can't wait to see how this thing works.

[LeonV]

I just ordered the Franck fuel level tool. I will set my fuel level with that first. I believe he says 25mm is ideal? I can't wait to see how this thing works.

It's a great tool, but might take a little practice to use. Dip it in and out of the fuel a few times and look inside the center of the PC tube. You'll get the hang of it quickly, it's an awesome tool!