engine and drivetrain Need Help! Weber DCOEs Running Rich on Mains. Can't Lean Them Out

[eurotrash]

Not sure what you have seen for calculating jetting, but here is a great page for building your carbs based on motor specifics.  super easy to understand and use..

 

http://cnx.org/contents/a0a6da11-6437-404f-8cd3-10853a08b685@2

 

And here is a great vintage sound bite about emulsion tube functionality..

 

 

https://www.youtube.com/watch?v=1pkFSA_rRFI

[dapbmw]

Did you set all 4 idle mixture screws properly?   Intake manifolds seating properly? Any vacuum leaks? Are all the ignition parts changed recently? Compression on all 4 cylinders are good and within specs? What base gaskets are you using in between the carb and manifold?  

 

Rule of thumb the last thing you want to blame are the carbs themselves. A new Weber DCOE out of the box does not need to have it's float adjusted as they are set correctly at the factory so that is the last thing you want to do.

 

You did not indicate if you had 40's or 45's , a 151 is a 40 DCOE and a 152 is a 45 DCOE .  Saw your jet settings some of them need to addressed. My recommendation are for stock and slightly modified engines (292 cam, 9.5 compression, header, free flow exhaust , etc).  45's work the best even for stock motors.

 

Choke - 32  It's fine but 34 is ideal, but you can deal with that later.

 

Idle Jet - 60F8  That is too big for a stock motor.  I usually drop idle jets of either f8 or f9 in 45, 50 or 55. Not all engines are the same so some will run better on some jet sizes than others. So how do you know if you have the right idle jets? Let's say you have the idle mixture screws all dialled in properly, so if you turn them clockwise or counter clockwise from the reference point the idle should go low on both instances if not then you need to either go up or down in.5 increments. Once you got it right, then you should be fine.

 

Main jet - 115 It's a bit small and you would lean out, it's better to run richer than leaner, spark plugs are cheaper to replace than motor that broke due to a lean running condition.  120, 125 or 130 are ideal.

 

Air corrector - 200  That is too big the engine would fall flat past 5K rpm. 170, 175 or 180 are ideal.

 

Emulsion tube - F11  F11's starts slower on progression phase, use F9 or F16 as you want to the progression phase from the idle jet to emulsion jet to start much earlier so they overlap each other and you won't have a flat spot or stumble at the 1500-2500 range. Emulsion tubes work on vacuum pressure their job is to meter and emulsify the fuel properly.

 

Pump jet - 40 That is fine but 45 is much better, better to run richer than leaner. You don't have to change this one if you prefer.

 

Needle valve: 175  That is a bit small, usually that size is for engines 1300-1600 cc.  200 is ideal.

 

As far as ignition timing, with side drafts you want a little bit of advance so from the reference just bump it a bit and to check it you have it right, it's must be run with a load as in driving it and see.

 

Hope this helps you out.

 

 

 

 

[Beach_Bum]

 

Not sure what you have seen for calculating jetting, but here is a great page for building your carbs based on motor specifics.  super easy to understand and use..

 

http://cnx.org/contents/a0a6da11-6437-404f-8cd3-10853a08b685@2

 

And here is a great vintage sound bite about emulsion tube functionality..

 

 

https://www.youtube.com/watch?v=1pkFSA_rRFI

 

 

Thanks man, I'll dive into that when I get some time.

 

Did you set all 4 idle mixture screws properly?   Intake manifolds seating properly? Any vacuum leaks? Are all the ignition parts changed recently? Compression on all 4 cylinders are good and within specs? What base gaskets are you using in between the carb and manifold?

 

Thanks for the input. To answer your questions...

 

- Carbs are brand new DCOE 40 (151)

- I have checked for vacuum leaks with starter fluid and did not find any.

- Ignition parts changed include: 002 Tii distributor with new Pertronix 1847V, new Karlyn-STI spark plug wires, I'm running NGK BP6ES plugs that have been on the car for about 3k miles before I installed these Webers

- Using standard DCOE base gaskets between carb and manifold

- Have not done compression test

 

Idle screws have been a bit of a problem. This is mainly why I'm using the 60F8 jets because I could not get the idle screws to do much with 45F9, 50F8, 55F9. With all of those jets, I had to turn out the screws at least 4-5 turns, and I was still getting lean popping from the carbs and AFR numbers in the 16-17 range at light cruise. With the 60F8 jets I'm still about 3 1/2 turn out, but I idle in the high 12s - Low 13s and light cruise AFR numbers are 13 - 14.5 I also tried 65F8 jets, but was too rich at idle and light cruise.

Edited March 24, 2015 by Beach_Bum

[Stevenola]

Report back when you've done the dirve sans air filters.

 

151's - are your air bypass valves closed all the way or at least one closed and the other balanced with the opposing barrel?

[Beach_Bum]

Report back when you've done the dirve sans air filters.

 

151's - are your air bypass valves closed all the way or at least one closed and the other balanced with the opposing barrel?

 

I will. New jet holder will be here tomorrow.

 

Yes, all of the bypass valves are closed all the way.

[Beach_Bum]

I had a chance to run the car tonight without the RamFlo filters.

- Steady cruise at anything under 3,000 RPM and my AFR numbers are 12.5 - 14

- Steady cruise at anything 3,000 RPM (~55 mph) and up and my AFR numbers are in the low 11s and the car bucks. If I step on the throttle from there in 4th gear, the AFRs go leaner to 12.5 - 13 range

- WOT from a rolling start through the gears and AFRs start in the 10s and Steadily go up to 12.5 right before I upshift at redline

These results are with the same jets as before...60f8, 115 main, 200 airs

I have to say, the car feels pretty good, minus the bucking at freeway cruise speeds. There's no hesitation and it pulls strong all the way through the RPMs. On the flip side of that, there is a pretty strong gas smell when I park it in the garage, and the highway cruise AFRs worry me a bit.

What should I do? Throw a fuel pressure gauge on it?

Edited March 26, 2015 by Beach_Bum

[Guest_anonymous]

Don't smoke in the garage

[Stevenola]

It appears these numbers are leaner than with the filters or no?

 

It also appears your overlap between idle and main jets is too much, in other words they're both contributing at +3k cruise.  When you go WOT, the idles run out and you are on full mains.  Low rpm cruise, you're still on idles.

 

I will look at your previous idle jet sizes and see if there is anything there.

Edited March 26, 2015 by Stevenola

[Stevenola]

Try again your 55f9 jets, even if you have to open the screws a little.  Then drive again as above and see what your numbers look like. 

[Beach_Bum]

It appears these numbers are leaner than with the filters or no?

 

It also appears your overlap between idle and main jets is too much, in other words they're both contributing at +3k cruise.  When you go WOT, the idles run out and you are on full mains.  Low rpm cruise, you're still on idles.

 

I will look at your previous idle jet sizes and see if there is anything there.

Yeah, everything seems good except for when cruising at freeway speeds. I forgot to add that it bucks too at these speeds. I've edited my post to reflect that. Also, I'm idling at 12.5 - ish and my screws are about 3-1/2 turns out. Thanks!

Edited March 26, 2015 by Beach_Bum

[Beach_Bum]

N/T

Edited March 26, 2015 by Beach_Bum

[Beach_Bum]

N/T

Edited March 26, 2015 by Beach_Bum

[downhillwolf]

Crusing speeds at what rpm? If throttle is open more than 1/3 then is compromise between idle and main circuit if more then its on mains... Try leaner air corrector... for above 3000rpm and f9 idle for lower rpm...
This measuments are for drive without filters?
I suggest you buy fuel pressure valve also electric facet pump is adviced, i will change it to facet pump because i drive car occasionally and fuel evaporates from carbs so i need to start it a bit more. I also have pressure valve and return line...

[Beach_Bum]

Crusing speeds at what rpm? If throttle is open more than 1/3 then is compromise between idle and main circuit if more then its on mains... Try leaner air corrector... for above 3000rpm and f9 idle for lower rpm...

This measuments are for drive without filters?

I suggest you buy fuel pressure valve also electric facet pump is adviced, i will change it to facet pump because i drive car occasionally and fuel evaporates from carbs so i need to start it a bit more. I also have pressure valve and return line...

 

Yes, this is driving without the filters. Cruising speed below 3,000 RPM and 1/3 throttle is good 12.5 - 14 on AFR. Cruising speed at, or above 3,000 RPM (55mph and above) and 1/3 throttle is too rich...low 11s and the car surges.

 

I'm going to try the 55F9 idles and report back. The weather is pretty crappy here today, so it may have to wait until tomorrow.

 

Thanks again for everyone's help!

[downhillwolf]

First thing i would try is replace emulsion tubes. Anyone from here lives near you, or from USA, so someone can borrow you F16 or F9 emulsion tubes... (postage from here to USA and back is as much as it would cost you to buy new emulsion tubes). idles should be fine 50f9...