Mixture always too rich- weber 44 idf's Options

[tornik550]

I have dual weber 44 idf's on my 2258. I was having a problem with one of my cylinders and found that the main circuit had some sort of black booger plugging most of the main circuit of cyl 2 and a small on in cyl 3. I completely cleaned everything and reassembled. The car is driving way better. I set the floats at 11.5 without the gasket.

Now I am having the other problem- my car is always too rich. At idle my a/f ratio is 13:1 which is ok for me. If I try to lean it out any more then I get popping on decel at low rpm's. On the main circuit, I am using 125 mains, f11 et, 210 ac and I am consistently around 10.2:1.

I can but smaller mains but it seems like I shouldn't need that small of mains.

My setup-

idles-50
mains-125
et-f11
ac- 210
vents- 34

Any ideas of how to lean the main circuit?

[Jackgerard]

Will the car pop when it is to rich or to lean cause my car pops too and I thoyght it was to rich.

[r_towle]

smaller vents, try 32mm.

increase the velocity of the air charge.

rich

[ThePaintedMan]

smaller vents, try 32mm.

increase the velocity of the air charge.

rich

(IMG:style_emoticons/default/agree.gif) If you're not able to introduce enough velocity through the carbs (even though it's a fairly large displacement motor) you're likely to see a rich condition across the RPM range.

[rhodyguy]

pulls like a demon @3k+ yes?

[tornik550]

pulls like a demon @3k+ yes?

YES!!!

[jmill]

If you're not able to introduce enough velocity through the carbs (even though it's a fairly large displacement motor) you're likely to see a rich condition across the RPM range.

You have that backwards. More velocity = more vacuum signal. Decreasing the vent size would increase the vacuum signal to the mains and cause an even richer mixture.

You can lean the main circuit by either increasing the AC jet size or reducing the main jet size or doing both. I agree that your jetting seems in the ballpark but your AFR says different. A 120 main and a 220 AC jet is also in the ballpark.

Popping on deceleration is usually caused by intake or exhaust leaks. Make sure everything is tightened up.

[ThePaintedMan]

Good call John. Must have read that wrong after a 12 hr day. That's actually a strange scenario with the main jets the OP has. Idle around 13 A/F ratio isn't horrible, but with a 125 main and an F11 ET, that would, in practice seem actually a little small. I run 135s on a 1.8 with an F11 ET. Any smaller on the mains would be on paper, too small, as would an A/C jet of anything larger than the 210 he has now. But in theory it would lean it out some.

What are the float levels like? Have you set them since the carbs have been on the car? How about fuel pressure?

[lonewolfe]

Which cam are your running and how are your heads setup?

[Jake Raby]

When an engine always runs rich I question exhaust efficiency and engine combination.

[rhodyguy]

good insight jake. thanks!

[r_towle]

good insight jake. thanks!

One proven way to deal with a situation like this is to match the vents and jets to the restrictive exhaust/heads/camshaft.

It's not magic.
Smaller vents and smaller fuel jets will make the setup function biased upon what the driver wants to do, driving style etc.

Having an air fuel gauge in situations like this is really helpful, but it can be done the old fashioned way by reading plugs and adjusting as you go.

To start with, I would reduce the size of the vents and tune from there.
It will be easier to tune down, and cheaper then headers, and exhaust.

Just my humble opinion....

Seems there are many opinions about carbs...
Seems like a simple issue to me....less air and less fuel for any given engine will make it run less rich....

One point that has not been discussed, or a missed it.
Is this a street car, a race car, or a bit of both?
Street setup 1-3k rpms typically is quite a bit different then a car tune for 4-6k rpms at the track..

[tornik550]

I decreased the size of my vents to 32 and the car seemed to respond we however my A/f ratios are still off. The other things that I noticed is that with larger vents, if I leaned out the carbs too much- I would get a pop on decel. Now it seems to pop earlier than it did with larger vents. I do not think this is a exhaust leak cause it does go away if I richen the condition slightly. I have also checked with a fog machine and didn't see a leak.

Also- some things that I forgot to mention is that I have 1 5/8 inch headers with a triad exhaust. The car is mainly used for spirited street driving. It seems like most of my driving is done older 3500rpm. I have a very wide variety of jets, vents, et. however the smallest mains that I have is 125 however I have ordered a bunch more so I will have smaller options soon.

[Dr Evil]

(IMG:style_emoticons/default/popcorn[1].gif)

[tornik550]

(IMG:style_emoticons/default/popcorn[1].gif)

Sooooo- have you moved to ohio yet? If so you wanna check out my new house (I may out you to work (IMG:style_emoticons/default/smile.gif)

[Dr Evil]

Looking at houses again next week. Last day at current job Oct 15 unless OH board of medicine holds slows the license down due to bureaucracy issues (IMG:style_emoticons/default/dry.gif) I hate dealing with bureaucracy.

All the places I look at have big man cave garages (IMG:style_emoticons/default/biggrin.gif)

[jmill]

By decreasing the vent size you just lowered the RPM at which you came on the main jets and enriched the mixture throughout the jet range. You also decreased your top end potential. I would have expected it to exacerbate your current problem. What was your AFR reading with the 32's?

The only reason I'd decrease the vent size would be to cure a lean transition issue or enhance low RPM drivability.

On a side note, my handy dandy chart says the 36 vent is right for you with a 6K redline. They should also lean out your mixture.

[tornik550]

By decreasing the vent size you just lowered the RPM at which you came on the main jets and enriched the mixture throughout the jet range. You also decreased your top end potential. I would have expected it to exacerbate your current problem. What was your AFR reading with the 32's?

The only reason I'd decrease the vent size would be to cure a lean transition issue or enhance low RPM drivability.

On a side note, my handy dandy chart says the 36 vent is right for you with a 6K redline. They should also lean out your mixture.

I think I'm gonna go back to my 36 vents. Last time I had then installed I had a lean transition zone however I also found that I had another carb issue which has now been fixed. Hopefully that will help.

Just curious- what ballpark jet sizes do you think I should need if I have 36 vents (just so I can get an idea if I am in the right range)

[jmill]

Initial jetting is always a SWAG and each engine is unique. My gut would say 140-150 mains but I would also never think you'd be at 10-1 with 125's and 34 vents.

I've had 2 sets of Weber 44's with 36 vents on 2 different engines (both 1914 cc's). Main jetting ranged from 135 to 165. 135's with 220 AC jets for the daily driver (Kombi Bus) and 165's with 190 AC jets on my 8,000 RPM drag bug.

I initially had lean transition problems with both of them. Almost lost an eyebrow from a lean pop on the bug. I stepped up to the 55 idle jet and F7 ET and never looked back. Love that ET.

In another thread Racer Chris mentioned increasing the AC jet size to bring the main jet in sooner which would help with lean transition. I've never tried it, it messes with my understanding of the AC jet somewhat but in theory might work. (Purely speculation here since trying to wrap my head around it) A larger AC jet (less restricted) should make it easier for a lower vacuum signal to pull air through the jet stack resulting in flow through the mains sooner.

My understanding was that the AC size didn't come into play until that size started to restrict airflow (higher RPM with more air volume travelling through AC jet). Small sizes restricted sooner, enrichening mixture and larger sizes restricted later giving you a leaner mixture.