No response to idle mix DCOE 40s - what would you try next?

[rcf925]

The diagram showed is not for Italian webers, They don't have cup and rubber o-ring under spring on idle screw

[Golfcar]

35 minutes ago, man_mark_7 said:

Yes, using an SK(?) sync. All the bores read just a hair over 5 at about 1300RPM.

Looking at original post I think most of your problem is this high idle. 

Idle screws have little or no effect at 1300 RPM. 

Get the idle down. The sync number is not important only used to compare each throttle to the others. 

Loosen the bolt on the dist, start the car, slowly turn the dist and listen to idle. Try to get down to 800 or so. 

You can't hurt anything here. It may stall and you may have to restart. 

Then go through and adjust the idle screws and see how it does. The long screws like this will be out 2.5 turns or more. 

You AFR numbers should be 12.5 +- My hopped up motor is at 11.5-12. 

AFR will probably never get above about 13.5 if it is jetted correctly. 

It will run like crap at 15 and above with no power. 

With the 123 you can set the timing advance low at start up as it makes it easier to start but at or above 3000 RPM it should be all in. 

Max Advance on the M10 is probably 35 degrees or more. 

Sorry still learning my M10 engine but my M30 which is very similar is at 36 degrees at full advance. 

Your working hard and I admire you for this. It's a steep learning curve but your getting there. 

Gary 

 

[man_mark_7]

1 hour ago, m5bb said:

Looking at original post I think most of your problem is this high idle. 

Idle screws have little or no effect at 1300 RPM. 

Get the idle down. The sync number is not important only used to compare each throttle to the others. 

Loosen the bolt on the dist, start the car, slowly turn the dist and listen to idle. Try to get down to 800 or so. 

You can't hurt anything here. It may stall and you may have to restart. 

Then go through and adjust the idle screws and see how it does. The long screws like this will be out 2.5 turns or more. 

You AFR numbers should be 12.5 +- My hopped up motor is at 11.5-12. 

AFR will probably never get above about 13.5 if it is jetted correctly. 

It will run like crap at 15 and above with no power. 

With the 123 you can set the timing advance low at start up as it makes it easier to start but at or above 3000 RPM it should be all in. 

Max Advance on the M10 is probably 35 degrees or more. 

Sorry still learning my M10 engine but my M30 which is very similar is at 36 degrees at full advance. 

Your working hard and I admire you for this. It's a steep learning curve but your getting there. 

Gary 

 

Thanks for the words of encouragement. I just keep remembering tuning prior cars and when something clicked and everything works right, it's a great feeling. 

 

I'm going to go play with the timing to see if I can reduce idle speed. Is it odd that it idled at around 900 with the 32/36 that this setup is replacing?

 

mm

[man_mark_7]

Retarded the timing about 5 degrees and that dropped the idle by ~500RPM - Nice! This (800RPM0 is as low as I can go right now. It does appear that a piece of the linkage might be contacting the carb body at this point w/ screw fully out. I'm going to let car cool down a bit, then check more closely. Don't know that I need to go much below this, but if i tweak some things and the RPM bumps back up i'll need to be able to close the plates more.*(see below)

 

At this RPM I now seem to have more or less equal response to the idle mix screws on all bores - Nice again.

 

On the other hand, after setting idle mix screws by listening to where engine doesn't increase RPM / run smoother when backing screws out, it seems to pop a lot more when I try to increase RPM using the throttle. - Not so nice. (too lean?) Am I correct that retarding timing too much can cause popping through the carb too?

 

I'm nearly ready to pull the carbs and confirm the throttle plates are fully closing. Is this true - *should they be really totally closed?! Doesn't a little bit or air need to leak in around them even at low RPMs? My 55f8 & 60f8 idle jets are due here tomorrow. If they don't help, then I guess i'll pull the carbs.

 

Thank you everyone for your help. I promise to keep posting until (and after) we've figured this out!

 

mm

 

 

[Golfcar]

14 minutes ago, man_mark_7 said:

Retarded the timing about 5 degrees and that dropped the idle by ~500RPM - Nice! This (800RPM0 is as low as I can go right now. It does appear that a piece of the linkage might be contacting the carb body at this point w/ screw fully out. I'm going to let car cool down a bit, then check more closely. Don't know that I need to go much below this, but if i tweak some things and the RPM bumps back up i'll need to be able to close the plates more.*(see below)

 

At this RPM I now seem to have more or less equal response to the idle mix screws on all bores - Nice again.

 

On the other hand, after setting idle mix screws by listening to where engine doesn't increase RPM / run smoother when backing screws out, it seems to pop a lot more when I try to increase RPM using the throttle. - Not so nice. (too lean?) Am I correct that retarding timing too much can cause popping through the carb too?

 

I'm nearly ready to pull the carbs and confirm the throttle plates are fully closing. Is this true - *should they be really totally closed?! Doesn't a little bit or air need to leak in around them even at low RPMs? My 55f8 & 60f8 idle jets are due here tomorrow. If they don't help, then I guess i'll pull the carbs.

 

Thank you everyone for your help. I promise to keep posting until (and after) we've figured this out!

 

mm

 

 

You're getting there Mark, good job. 

Yes, the throttle plates will be closed in an ideal setup. Webers have their own idle circuit and don't need an open butterfly and in fact that is what can make them so hard to get set at idle. Took me a long time to get this straight. Make sure the screws on the side that open and close the butterflies are out all the way. Not keeping the butterflies open. It's hard to get to this point sometimes. 

Popping is usually too lean. I doubt you've moved the timing enough to cause that. It takes a lot. 

Open those idle screws a little at a time. Even 1/8 of a turn can change it. 

You're getting close. 

Gary 

 

[man_mark_7]

3 hours ago, rcf925 said:

The diagram showed is not for Italian webers, They don't have cup and rubber o-ring under spring on idle screw

Thanks - I did a little research on this. Seems you are absolutely correct. 

 

The needles with the o-rings look like this and have a stepped tip. My needle type is shown below. Is this correct for a 151? Yes, it has a spring, I just didn't show it.

[man_mark_7]

One last bit of odd info. The carb top plates say "Weber Italy", but they have plastic floats and the air bypass screws. Pierce seems to indicate that "Italian" webers were all brass float? Do I have a hodge-podge of Italian and Spanish webers?

 

https://www.piercemanifolds.com/category_s/484.htm

 

thx

 

 

[jp5Touring]

Maybe you have this.

https://www.carburetion.com/diags/40DCOEDiaginfo.asp

 

Mine are 40-2 not 151 with brass floats made in Italy.  With no needle o-ring or the brass cup.

 

I'm no expert ? have a couple members message me has been great help.

Good luck with this,I have great interest.  

 

[edgefinder]

I know you have a synchrometer but you should also try a short length of hose around 1/2" diameter, one end at carb throat and one end at your ear. If you hear an odd sound from one throat it can help with diagnosis. Its also an easy way to synchronize if meter doesn't fit

[man_mark_7]

3 hours ago, jp5Touring said:

Maybe you have this.

https://www.carburetion.com/diags/40DCOEDiaginfo.asp

 

Mine are 40-2 not 151 with brass floats made in Italy.  With no needle o-ring or the brass cup.

 

I'm no expert ? have a couple members message me has been great help.

Good luck with this,I have great interest.  

 

Yes - it looks exactly like this, plastic floats and all. My question was, did someone swap an "Italian" weber float cover onto this type of carb? Were any 151s made in Italy?

[man_mark_7]

2 hours ago, edgefinder said:

I know you have a synchrometer but you should also try a short length of hose around 1/2" diameter, one end at carb throat and one end at your ear. If you hear an odd sound from one throat it can help with diagnosis. Its also an easy way to synchronize if meter doesn't fit

 

Thanks - will try this! I find that if i angle the SK sync meter just right I can get it to fully seal in all the trumpets (holding it at the same angle for all of them) and just barely avoid my Tii booster.

[Golfcar]

4 hours ago, man_mark_7 said:

 

Thanks - will try this! I find that if i angle the SK sync meter just right I can get it to fully seal in all the trumpets (holding it at the same angle for all of them) and just barely avoid my Tii booster.

You can make a manifold out of cardboard to put on the synchrometer to make it fit better to the webers. Just tape it to front of sync meter. 

The hole size is not that important as you are just using the sync to measure the flow and see if each carb is the same. 

Weber parts mixed up. Weird. 

Still though you are getting there.

Once you get a good idle and smoothness then drive the car and see how it runs. 

Can you watch the AFR and still drive? 

I have my gauge in my center console. 

Watch carefully.... when you accelerate the value should go lower like to 11 because the accelerator pump has activated but only for the movement of the pump. A second or two.  Now continue to test and stomp on it. AFR should go 11 or maybe even high tens. See how smooth it is and notice RPM of any flat spots. Also note how the power feels. 

Give us some feedback and will go back and look at jetting. 

Also see if it is popping a lot on deceleration. 

We'll evaluate then. 

Good luck! 

Gary  

[man_mark_7]

Well - New idle jets did arrive today, but I messed up and only ordered 2ea of 55s and 60s. Don't know what I was thinking. I managed to get an order in early enough for Pegasus to ship more jets today so I should receive them by Friday. Will give me something to play with over the weekend.

[Golfcar]

1 hour ago, man_mark_7 said:

Well - New idle jets did arrive today, but I messed up and only ordered 2ea of 55s and 60s. Don't know what I was thinking. I managed to get an order in early enough for Pegasus to ship more jets today so I should receive them by Friday. Will give me something to play with over the weekend.

Like I said if you're going bigger get a drill set from Pierce or another. It's easy and it's done in a few minutes, no waiting a week for a delivery. 

[Golfcar]

This is my M30 motor in my 3.0 CS. 

I built this in 2014. 

10.5:1 pistons.

Custom cam. 

Headers 

Larger valves. 

B35 head, the best one for this motor. 

Dual valve springs with titanium retainers. 

All custom balanced. 

Lightened flywheel 

45 DCOE Webers

123 ignition