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

[downhillwolf]

You have a deal with 2 gasoline reservoirs, and 4 carburetors. So if you have too high fuel pressure and one of the needle valves gave up you have one carb floded and other lean...
But i must advise you to go by steps. Checking everything to be OK starting with fuel pressure to be good at all rpms. Only then you can surely determine what should be wrong...
We could advise you here hundred things but it may not be OK and you ll lose some serius amount of $.
Start by checking this:

-fuel pressure regulator

-Check fuel level on both(the same height)
-F16 emulsion tubes
-synchronisation(check it again)
-distributor advance

-...

Are your carbs new from store or second hand? If so, check each if they have same progression holes(covers with codes like yours 40DCOE151 can be changed)...

P.S.: If fuel pressure is a little over 4psi, at high rpm vibrations from engine can make needle valve failiure and one carb is floded. Once i tested one carb on my working table with too much fuel pressure it holded, but on car it was floded... Not new carb but old one...

Edited March 28, 2015 by downhillwolf

[Beach_Bum]

I hear you, already spent a bunch in jets. To answer some of your question:

- Carbs are brand new DCOE 151

- Both carbs fuel level is at 28.5mm measured with a Micrometer from the machined surface where the jets sit until the fuel "jumps" at me

- Distributor advance is 30 degrees at 2000 RPM

- Needle valve moves smoothly. Checked multiple times when adjusting float heights

One thing I've noticed is that DCOE 151s have two types of top covet gaskets. One is paper and one is a rubber material. I have the paper gasket and it is very thin. I'm not sure if the recommended float settings of 12.5mm/25mm are with the paper or rubber. I suspect rubber, which is probably a bit thicker than my paper one, but I'm not sure if that would make any difference anyway. Just wanted to throw it out there.

[downhillwolf]

I im measuring on my brass floats with gasket always on. So then is really a micrometers difference with paper or rubber gasket(only pressure deformation of gasket).
Anyway fuel pressure regulator is what you need. At 3000rpm at 13AFR pooping is a bit strange... looks like you have one reservoir too full... Just to give that out of equation and anyway you will need it even if you decide to go on electric fuel pump...

[Stevenola]

Measuring floats when they are in the car is more accurate than the book method & ruler.  Just keep the float drop the same for each.  So you've got that covered.

 

I thought you had an electric pump - so under 4psi at idle is good (like others say, it could be 3 or so as long as the volume is there) - what does it go to at higer revs?  A fuel regulator may be in order if it's higher.  I run a Carter p4070 pump and a Holley regulator.  Lots of volume and low pressure. 3psi.

 

Can you observe your fuel pressure while driving?

 

Since you've measured from the top of the carbs you've already accounted for gasket thickness.  The original method is based on paper gaskets.  I also measure floats from the top and run rubber gaskets and they eliminated all gas seepage and most of the fuel odor under the hood.  I highly recommend them. 

 

You're richer now at WOT so put the smaller mains in and let's see what the e-tubes do.

 

 

I hear you, already spent a bunch in jets. To answer some of your question:

- Carbs are brand new DCOE 151
- Both carbs fuel level is at 28.5mm measured with a Micrometer from the machined surface where the jets sit until the fuel "jumps" at me
- Distributor advance is 30 degrees at 2000 RPM
- Needle valve moves smoothly. Checked multiple times when adjusting float heights

One thing I've noticed is that DCOE 151s have two types of top covet gaskets. One is paper and one is a rubber material. I have the paper gasket and it is very thin. I'm not sure if the recommended float settings of 12.5mm/25mm are with the paper or rubber. I suspect rubber, which is probably a bit thicker than my paper one, but I'm not sure if that would make any difference anyway. Just wanted to throw it out there.

Edited March 29, 2015 by Stevenola

[Beach_Bum]

Measuring floats when they are in the car is more accurate than the book method & ruler.  Just keep the float drop the same for each.  So you've got that covered.

 

I thought you had an electric pump - so under 4psi at idle is good (like others say, it could be 3 or so as long as the volume is there) - what does it go to at higer revs?  A fuel regulator may be in order if it's higher.  I run a Carter p4070 pump and a Holley regulator.  Lots of volume and low pressure. 3psi.

 

Can you observe your fuel pressure while driving?

 

Since you've measured from the top of the carbs you've already accounted for gasket thickness.  The original method is based on paper gaskets.  I also measure floats from the top and run rubber gaskets and they eliminated all gas seepage and most of the fuel odor under the hood.  I highly recommend them. 

 

You're richer now at WOT so put the smaller mains in and let's see what the e-tubes do.

I haven't checked the fuel pressure at higher revs, and I don't have any way of checking it while driving, but if the E-tubes don't help I'll put that on my list. I think I will order a set of the rubber gaskets because the fuel smell from the engine bay after driving is really strong.

Thanks again for everyone's help, you guys are awesome! I'm hoping to have the E-tubes by Tuesday and the IE stacks/filters by Wednesday and will report back after installing them.

[73tiiguy]

Hey Bum, what an adventure your having.  I'm pretty happy with my 40's on a stock 2.0L - no headers or aftermarket exhaust.  Mine popped a bit while driving too.  I fiddled with synchronization until I knew it was as good as it will ever be.  I then adjusted the engine timing (tried a little advance or retard) until the popping went away - Yes, the Italian way   did the same with my Tii and every other old car I've ever owned.  Nothing like a road test to give you the required feed back.

 

Your motor is stock with IE full exhaust - If I were you, I'd maybe go back to the jets and tubes loaded up by weber/redline. 

 

Also (not that I think this is your core issue), have you checked your ignition dwell? 52-53 degrees just to be sure the pertronix ignition is OK.

[Beach_Bum]

Hey Bum, what an adventure your having.  I'm pretty happy with my 40's on a stock 2.0L - no headers or aftermarket exhaust.  Mine popped a bit while driving too.  I fiddled with synchronization until I knew it was as good as it will ever be.  I then adjusted the engine timing (tried a little advance or retard) until the popping went away - Yes, the Italian way   did the same with my Tii and every other old car I've ever owned.  Nothing like a road test to give you the required feed back.

 

Your motor is stock with IE full exhaust - If I were you, I'd maybe go back to the jets and tubes loaded up by weber/redline. 

 

Also (not that I think this is your core issue), have you checked your ignition dwell? 52-53 degrees just to be sure the pertronix ignition is OK.

 

Yes it is quite the adventure Not necessarily the one I wanted to take, but I am learning a lot about the carbs.

 

I'm actually running most of the jets that came with the carbs minus the idles. They came with 45F9 and I'm currently running 55F9. Have not checked dwell

[zinz]

As I remember, Jeff, you are running a Tii dizzy with a Pertronix igniter? With that setup, there is no dwell to check. 

 

whew... this really has turned into an adventure for you.  I had hoped you'd be set by now. But it is so very good to see the amount of assistance your are getting from the others here on FAQ.

 

I am curious about your AFR #s... Steve and I have been bouncing some general things around about carbs and WBO2 sensors... Here we are using a precision sensor to read AFR, but we use a "toilet bowl" to deliver the fuel.... I'm not saying we can't get good AFR#s across a broad range, but even the best carburetor will only be most efficient in narrow power band; that's just the nature of the beast.  You are right in trying to pursue the best jetting, but also know that you might never find perfection across all parameters.  Personally, I think your idle jet is too small, because your have to set the idle screws too many turns out...  But we've already been down that path a couple weeks ago.  There MUST be a middle ground somewhere, right?

 

Now... I've been thinking about with your problem of being rich at cruise.  For 2 years I've been using an aftermarket Tii dizzy with no vacuum advance and have had a consistent stumbling/over-rich at cruise and especially when decelerating to a stop from say... 45mph+.  I was always needing to blip the throttles to clear the fuel bog.  I now have the programmable 123Ignition distributer with a vacuum port and I can program a vacuum advance into the dizzy. Guess what??? Allllllll of that stumbling/over-richness has disappeared. Why?  Because I am now able to light that air-fuel mixture at part-throttle with a properly advanced ignition curve.

 

Soooo... perhaps you are experiencing the old "90% of your carb problems are ignition-related?"  I don't know... but it could be a piece of the puzzle.  The DCOE gurus here are obviously providing a lot of useful jetting info and you are obviously not intimidated to get it right.  Am I saying you need a $500 distributer? No.  Plenty of folks run sidedrafts without a vacuum-advance dizzy.  We just need to figure out what's going on with YOUR carbs.

 

Have you done some plug chops?  The WBO2 will tell you the AFR in the entire exhaust plume, but it will not differentiate if one carb is running richer/leaner than the other.  Checking plug color/condition will tell you immediately which cylinder is acting up.  Since you know there is some imbalance somewhere between the carbs, I'd find an empty stretch of road to run the car at high cruise, then kill the motor, coast to a safe spot and pull the plugs and determine if you have richness in all cylinders or just one or two, and if they are on the same carburetor.  This exercise only takes a few minutes but provides invaluable information about running condition of individual cylinders.

 

Keep pushing... we'll get your carbs figured out!!!

 

Ed Z

[Beach_Bum]

F16 Emulsion tubes showed up today. Earlier than expected thanks to Pierce's quick shipping.

Here's what I found tonight. These results are still with standard velocity stacks and no filters:

F16 em tubes

55f9 idles

115 main

200 air

Idle screws 4 turns out

Idle AFR 12-12.5

Cruising at 2500 rpm 14-15 with some surging

Cruising at 3000 rpm 12.5-13

Cruising at 65-70 mph (3500 rpm) 12-12.5

WOT 13.5

Accelerating through gears normally normally:average of 13.5

I'm pretty happy with theses numbers and the way the car drives (minus the surging at 2500) and I'm sure dar_on tell me to leave it alone BUT I can't help thinking that I'm just masking a bigger problem by using small mains and very large airs. One member told me offline that I'll damage the motor in the long run if I keep running these jets. Any truth to this even though the AFRs are good?

I also tried some other jets just to see:

F16 em tubes

60f8 idles

120 main

175 air

Idle screws 3-1/2 turns out

Idle AFR 12-12.5

Cruising at 2500 rpm 13.5-14 some surging

Cruising at 3000 rpm 10.5-11 some surging

Cruising at 65-70 (3500 rpm) low 11s

WOT 10.5-11

Accelerating through gears normally 11s

Here are some of my thoughts and concerns. I'm far from knowledgeable on this stuff so please correct me if I'm wrong.

First, I'm concerned about the number of turns out on my idle screws. 4 turns seems excessive. The car won't idle properly without it though. Also, if I go from screw to screw and separately turn each one clockwise one turn the idle stumbles each time, but if I turn the screw counterclockwise one turn, no stumble. According to Dap, it should stumble either way you turn.

Secondly, the more I think about it, the more I'm leaning towards the fuel pressure being too high. If it's idling at almost 4psi, then surely when it revs it's greater than that. After looking into it last night, seems that DCOEs like pressure up to 3.5psi. I may buy one of the cheap hockey puck regulators from Pep Boys just to see if it makes a difference. Problem is, since I'm using the Bavaria pump, It would have to be hanging in-line between the pump and carbs. Not sure if that's ok, because it has some weight to it.

[Beach_Bum]

 

Keep pushing... we'll get your carbs figured out!!!

 

Ed Z

Thanks for the encouragement Ed. I sure hope we can get all of this figured out...very frustrating!

I agree about the AFRs, and I'm not trying to get them perfect across the board (although that would be nice), just trying to find a happy medium somewhere. As I said above, I would be happy where they're at but I feel like I'm masking a bigger problem by running small mains, large airs, and an idle jet that is too many turns out.

Interesting about the 123 distributor. I've actually been following that thread, but most of the conversation is over my head It's definitely something for me to keep in mind for the future.

[Stevenola]

Pierce is great, order on Sunday, arrive on Wed.  The best investment I made was a set of jet drill bits, saves a bunch of money.

 

Try to only change one thing at a time, it is easier to trace problems/results that way.  I like your first batch of numbers so perhaps go back to those.

 

Adjust for best lean idle then turn in the idle screw to about 1800 rpm.  Open and close the mixture screws to see how it affects rpm.  If by opening them you get an increase in rpm then your jets are too small or you have a vacuum leak that bigger jets are compensating for.  Check the throttle shaft bearings and the mixture screws for air leaks (you've already checked the mainfolds and gaskets, yes?).  Grease the threads of the idle screws to ensure an air tight fit if suspect.  Put the 60's back in with the 115 main and see what the 2500 rpm cruise is.

 

I have found a rich stumble is harder to detect than a lean one when adjusting the mix screws.  I just go in until stumble/rpm drop then back out 1/4 or so to get in ballpark.

 

Go to 160 air correctors to see about getting the wot down to 12.5.  I have extra jets if you need some.

 

I think Ed Z has a mechanical pump which works but he has Solex's so maybe that's different.  If your pressure is wack at higher rpm consider the standard electric pump and regulator most DCOE users have.

 

Accel pumps contribute to the main mix, what size are yours and what is your bleed valve size?  Do the pump jets have the little washers to seal them to the body?

 

Edited March 31, 2015 by Stevenola

[Guest_anonymous]

I'm pretty happy with theses numbers and the way the car drives (minus the surging at 2500) and I'm sure dar_on tell me to leave it alone

 

 

I love plug chops, maybe its a motocross thing, just don't turn the key all the way back and lock your steering. BAD JUJU

[zinz]

Yikes... Important safety tip I failed to mention. Thanks, Daron.

[zinz]

With soooo many different combinations you have tried and the carbs are still showing evidence of richness, I believe you are correct in thinking you are masking an underlying problem...it's gotta be the Pierburg.

 

You have fuel pressure of 4psi at idle?  That's too much.  I should have sent my regulator to you last week....  Run down to your local parts store and get a Mr Gasket hockey puck regulator and I'll buy the beers if that doesn't solve your problem.

 

Ed Z

[Stevenola]

Another option is the Holley 12-084, it goes from 1-4 psi perfect for side drafts.

 

With soooo many different combinations you have tried and the carbs are still showing evidence of richness, I believe you are correct in thinking you are masking an underlying problem...it's gotta be the Pierburg.

 

You have fuel pressure of 4psi at idle?  That's too much.  I should have sent my regulator to you last week....  Run down to your local parts store and get a Mr Gasket hockey puck regulator and I'll buy the beers if that doesn't solve your problem.

 

Ed Z