Wideband A/F help - 3x Webers running very rich

[Stevehose]

I installed a wideband gauge as the next step in trying to get my triple webers set up. My numbers are from what I've read on the internet, atrocious.

Lean best idle = 11.7
Hard acceleration = 11.5-12.5
WOT = 12
Cruise at 3500 rpm = 12.5
Over run = 13.5

I can't get the idle above 11.7, I have different idle jets and it seems the engine simply likes this number no matter what. Idles smoothly.

Here are my current specs:

40DCOE32 carb
4.5 aux venturi
32mm choke
125 main jet
F9 emulsion tube
200 air jet
50F9 idle jet
40 pump jet
60 pump bleed
200 float needle valve

Timing is 14BTC at idle and 34BTC all in.

2 things - I have new 32mm chokes because I was missing one when I bought them and the size of the exising ones was unidentifiable. Should I be running 34mm chokes for these jets? Would larger chokes lean up the overall powerband? Although very rich, the readings are pretty consistent throughout the rev range. Are smaller chokes sucking more fuel mixture in as well as sooner?

It does not like leaner idle jets, I tried F8 and it spit at me.

Should I try a smaller main? Seems like I already have a wide diparity between the 125 main and the 200 air jets.

Runs well, but rich obviously, with no smoke out the exhaust. No bogs or transitional issues - revs nicely.

Suggestions?

 

[DaveG]

Which WB did you use? The LC-1 won't read correctly unless you do the free air calibration...Not sure how the others handle that....
DaveG

 

[DaveG]

The f numbers on the idle jet denote the air correction holes.... Try a 45F9 idle jet.... That is one step leaner on the fuel side. Webers typically cruise on the idle jet. The mains only work fully at high power. At WOT the pump jet gets into the act as well...
DaveG

 

[Stevehose]

I have the LC-1 and I did the free air calibration before installing per the instructions.

Which WB did you use? The LC-1 won't read correctly unless you do the free air calibration...Not sure how the others handle that....
DaveG

 

[Stevehose]

Duly noted, perhaps my mains are also activating sooner - I will pull the main jets and see how far the idles take me.

The f numbers on the idle jet denote the air correction holes.... Try a 45F9 idle jet.... That is one step leaner on the fuel side. Webers typically cruise on the idle jet. The mains only work fully at high power. At WOT the pump jet gets into the act as well...
DaveG

 

[kasbatts]

My 2 cents worth,

your possibly trying to save money by tuning yourself and / or your enjoying the challenge, but after may years of racing and playing with cars with DCOE carbs, the best thing you can do is find someone who knows what there doing that has a dyno / rolling road and have them tune for you, doing it yourself and getting it wrong can lead to tears
Mixture to rich and you end up with washed bores which leads to bore wear problems, to lean and you will melt pistons or valves, I know you have your air / fuel ratio meter to help, but these carbs are complex beasties to get right all the way through the rev range.

Dyno tuning was for me money well spent, in all the years with these carbs I never had a problem, all I had to do was do the balance and adjust the idle mixture occasionally.

Job done!

 

[Stevehose]

Installing webers and saving money are mutually exclusive lol. That's a great idea but unfortunately where I live the rare dyno shops are not familiar with what a carburetor is. I'd do that in a heartbeat if I lived in CA.

My 2 cents worth,

your possibly trying to save money by tuning yourself and / or your enjoying the challenge, but after may years of racing and playing with cars with DCOE carbs, the best thing you can do is find someone who knows what there doing that has a dyno / rolling road and have them tune for you, doing it yourself and getting it wrong can lead to tears
Mixture to rich and you end up with washed bores which leads to bore wear problems, to lean and you will melt pistons or valves, I know you have your air / fuel ratio meter to help, but these carbs are complex beasties to get right all the way through the rev range.

Dyno tuning was for me money well spent, in all the years with these carbs I never had a problem, all I had to do was do the balance and adjust the idle mixture occasionally.

Job done!

 

[kasbatts]

Ah, ok, so the next best thing I guess ( and you may have done this) is to start with the same set up that some of the other guys have, maybe take a look at the choke and jet specs of three different cars to try and hit on some kind of average set up ( guys with DCOE's please help here, all info much appreciated) then fine tune from there

Some good sites on the web

Just found these which have all the right info for a good start


joltfreak.tripod.com

cnx.org/content/m37431/latest/

 

[61porsche]

Idle

scews are where?

Don't get fooled by best lean. The object is where are the butterflies in relation to the progression holes. Small adjustments to enable the edge of the butterfly to slightly open. Very small. Try a larger air jet.

The old tuners would actually scrape the butterfly away for more air.

What are your floats set at? Lower them a smidge.

If you're averaging 12.5 that's fine.

 

[kasbatts]

Another thing to check is fuel pressure and volume, (you probably have enough volume) but these carbs don't like much fuel pressure, only 3.5 psi max, any more and the float valves get pushed of their seats, this can lead to nastiness !!
FIRE! I learnt the hard way when I first got my DCOE's ( managed to put it out.. Lucky!) make sure pressure is right.. Very very important, And buy a fire extinguisher and keep in the car at all times!!

 

[Stevehose]

Yep - 3.5 lbs regulated from the Carter pump. Fire extinguisher in driver's footwell!

Another thing to check is fuel pressure and volume, (you probably have enough volume) but these carbs don't like much fuel pressure, only 3.5 psi max, any more and the float valves get pushed of their seats, this can lead to nastiness !!
FIRE! I learnt the hard way when I first got my DCOE's ( managed to put it out.. Lucky!) make sure pressure is right.. Very very important, And buy a fire extinguisher and keep in the car at all times!!

 

[Stevehose]

Yes I am close to the other guys' setups except for my32 vs their 34 mm chokes which is why I was wondering if the smaller ones would draw more fuel through similar jets?

Ah, ok, so the next best thing I guess ( and you may have done this) is to start with the same set up that some of the other guys have, maybe take a look at the choke and jet specs of three different cars to try and hit on some kind of average set up ( guys with DCOE's please help here, all info much appreciated) then fine tune from there

Some good sites on the web

Just found these which have all the right info for a good start


joltfreak.tripod.com

cnx.org/content/m37431/latest/

 

[Stevehose]

My butterflies cover the first progression hole per spec, I have been closing throttle plates to about 800rpm to set the mixtures then bring the idle up to 1000 and tweak 1/8 turn or so to where I will keep it at 1000rpm-doing this doesn't affect the AFR reading but it does eliminate any pops during initial revs. Screws are about 3/4 out, when I put the leaner 50F8 in place of the 50F9 it spit which I think is why DaveG suggested trying a leaner 45F9 size for the fuel inlet side. When I had the 50F8 in there I had to back out the mixture screws to compensate which is what the books all say would happen.

My floats are set at spec 8.5mm with 6.5mm travel. How much should I lower them, and should I keep the same travel or just reduce the level?

Right now at average 12.5 I am getting the black powdery exhaust pipe deposits, otherwise it seemingly runs well with no fuel odors.

Thanks.

scews are where?

Don't get fooled by best lean. The object is where are the butterflies in relation to the progression holes. Small adjustments to enable the edge of the butterfly to slightly open. Very small. Try a larger air jet.

The old tuners would actually scrape the butterfly away for more air.

What are your floats set at? Lower them a smidge.

If you're averaging 12.5 that's fine.

 

[61porsche]

Where is you OX sender? Exactly? Got a infrared thermometer to see if one downpipe is hotter than the other?

Drop the level no more than 1mm.

Yes, smaller chokes move faster at lower rpms- that's why your torque is better vs larger. Think of it as similar to a cam where it shifts power upward to make use of increasaed hp. Smaller chokes- more torque down low. Less hp up top ( past 5500) not an issue for you till you change cams, etc.

The progression hole- Think of that hole being slightly uncovered vs. covered. Uncovered to let more air to lean. That small area is what the books don't tell you about.

Are you sure it's all carbs and not one? Like the rear.( Statistical probability due to engine cant.) Other wise go back to that one. Leaking pump, ball not seating? The specific gravity of fuels is not what Weber had in mind- the recommended float level was for ancient fuel. Yes, they had that part down cold, like zeniths that float had better be a specific weight. Pulsing- are you detecting any? New needles? Get some dental floss on your air jets and idles- yeah sounds stupid. Don't trust the stampings on your jets. Buy a cheap VW jet guage/ reamer set. You don't know what you don't know.

What's your fuel pressure? 2.5?

Spark- what coil? More spark, longer duration, wider gaps, different range plugs? What do yours look like?

Initial advance at what rpm? Let's say that those webers like more -say 16 would be normal for mechanical advance dizzy typical sweet spot.

What rpm and advance are you at at 12.5?

Wideband and numbers-what wideband meter? Is it digital? Is the Ox heated? Remember a modern engine is going to run much hotter.

Drop your octane.

Take those o-rings off and see if you can get a bit more air.

 

[Stevehose]

Answers and more questions

Where is you OX sender? Exactly?

It's in the piece of pipe that replaced the middle resonator. Seems to respond quickly to slight mixture adjustments with minimal lag time.

Drop the level no more than 1mm.

I made a dipstick to check float level and it is not too high, if anything they all are a little low by a mm or two.

Yes, smaller chokes move faster at lower rpms- that's why your torque is better vs larger. Think of it as similar to a cam where it shifts power upward to make use of increasaed hp. Smaller chokes- more torque down low. Less hp up top ( past 5500) not an issue for you till you change cams, etc.

My idle jets finally crap out at 3800 rpm, wouldn't a larger choke lean this and the mains out, regardless effect on low end touque?

The progression hole- Think of that hole being slightly uncovered vs. covered. Uncovered to let more air to lean. That small area is what the books don't tell you about.

Uncovering the first progression hole doesn't seem to lean it out, it just raises the idle because mixture is then drawn from that hole as well as the idle mixture hole. I would think this would work if a hole was drilled in the fully closed butterfly, but as soon as it's opened then the first of 3 progression holes kick in.

Are you sure it's all carbs and not one? Like the rear.( Statistical probability due to engine cant.)

All carbs appear to be working and adjusting correctly, the 3rd responds very well to adjustments and it's float level looks ok.

Other wise go back to that one. Leaking pump, ball not seating?

I will check for leaking accelerator pump tubes, although it seems unlikely that all would be leaking.

Pulsing- are you detecting any? No.

New needles? Yes.

Get some dental floss on your air jets and idles- yeah sounds stupid. Don't trust the stampings on your jets. Buy a cheap VW jet guage/ reamer set. You don't know what you don't know.

I cleaned them when rebuilt but who knows....

What's your fuel pressure? 2.5? It's 3-3.5 I forgot exactly what I set it at-doesn't seem too much - no spilling of fuel etc.

Spark- what coil? Bosch red with pertronix, gapped at .025


More spark, longer duration, wider gaps, different range plugs? What do yours look like? I run Bosch W8DC - hotter due to my primary city driving and my car has loved them in the past.

Plug insulators are not totally black but there are deposits of carbon on the threaded portion.

Initial advance at what rpm? Let's say that those webers like more -say 16 would be normal for mechanical advance dizzy typical sweet spot. 14 at 1000RPM and 34 all in.

What rpm and advance are you at at 12.5? Don't remember but probably 3400rpm full advance.

Wideband and numbers-what wideband meter? Is it digital? Is the Ox heated? Remember a modern engine is going to run much hotter. Digital Innovate LC-1 with heated bosch O2 sensor, calibrated before install.

Drop your octane. Please explain this?

Take those o-rings off and see if you can get a bit more air. Will do on next round.

I have F9 emulsion tubes, the book by Pat Braden lists the 6cyl BMW using an F11 tube and 45F9 idle jets which are both leaner - thoughts?

THANKS!

 

[61porsche]

mmm... more suggestions

. Did your water temperature change? Colder.

Chokes- In theory yes. In practice, both are near the same flow curve and at some point you're chasing your tail. ( back to rejetting, etc.)

Don't drill.

Drop your fuel pressure.

Open your plug gap to .28 and or get a hotter coil.

Plugs a little dark, but not bad. Take it for a hard run and then look.

You can try the others, If you can get near to 13, 13.5 quit.

Octane- your gas. Mid grade and lower actually burns hotter. You could hook up your lawn mower gas can!