Is my engine really at TDC?

[vraned]

David, based on your exhaust note and the pics of your plugs it looks like you are dropping #3. Check the #3 wire and #3 position on the cap. If you are running pertronix, you should swap in a different ring, or put your primary coil signal on a scope to make sure that all of the magnets in the pertronix rotor are healthy. With my most recently purchased pertronix I could not get the coupe to idle smoothly. I swapped in the ring from my bavaria and it idled perfectly. The attached pics show what I found when I put the suspect setup on the scope. The pronounced gap in the signal chain is a defective/missing magnet in the pertronix ring. I ended up ordering a replacement ring from Jegs for about $25. The defective ring now resides on my refrigerator.

deQuincy, your plugs meet the Colin Campbell definition of perfection: "light brown or greyish tan deposits on insulator nose."

 

[David]

Wow. I am honored to have your input on my humble couple. The work on yours is second to none.

I don't have a scope, but I'll swing by Mesa Performance tomorrow to order a new ring. Thanks for your help.

-David
P.S. For anyone looking for humbling inspiration, check out vrandes work:
http://www.vranedom.com/

 

[Stevehose]

While idling, put your hand over the secondary barrels, if the idle changes a lot then the throttle plate is open at idle. I will check my Weber book tonight to verify if it should be fully closed at idle and not drawing that much air, there is an adjustment screw on the secondary linkage for this purpose. Open secondaries will cause poor idle, transition, mixture, weak power, etc. I had this issue with my Zeniths.

 

[Stevehose]

According to the STE synchometer instructions, the flow rate at idle for a weber secondary should be between 1.8 and 2.5 kgh at idle and low rpm.

The Weber manual says to adust the secondary throttle valve gap between the outer edge of the valve and the barrel to .05mm (.0002 in.).

While idling, put your hand over the secondary barrels, if the idle changes a lot then the throttle plate is open at idle. I will check my Weber book tonight to verify if it should be fully closed at idle and not drawing that much air, there is an adjustment screw on the secondary linkage for this purpose. Open secondaries will cause poor idle, transition, mixture, weak power, etc. I had this issue with my Zeniths.

 

[David]

While idling, put your hand over the secondary barrels, if the idle changes a lot then the throttle plate is open at idle. I will check my Weber book tonight to verify if it should be fully closed at idle and not drawing that much air, there is an adjustment screw on the secondary linkage for this purpose. Open secondaries will cause poor idle, transition, mixture, weak power, etc. I had this issue with my Zeniths.

Thanks Steve. As always, very helpful. But where is the secondary linkage idle screw ? Is that 72 in this image ? It looks like you access that from under the carb.

http://www.carburetion.com/diags/3236DGAVDiaginfo.asp

 

[Stevehose]

That's the screw, but I don't have those Webers so I don't know how/where to access it. On my old Zeniths I think I could get to it by opening the throttles all the way and getting a very small screwdriver in there somehow. Same with the cold idle adjustment.

How much gap do your secondaries have now? Not really sure what to accurately measure it with, the tiny gap is likely set in order to prevent the valve from binding in the barrel. If you can get to the screw then maybe loosen it with the air flow meter as your guide.

Thanks Steve. As always, very helpful. But where is the secondary linkage idle screw ? Is that 72 in this image ? It looks like you access that from under the carb.

http://www.carburetion.com/diags/3236DGAVDiaginfo.asp

 

[deQuincey]

Somewhat. It is better. Click on this to hear the idle:

http://s627.photobucket.com/user/david91107/media/E9/IMG_1342.mp4.html

hi david,
yes better, you are on the right way

as promissed, here is a link to a video to hear my iddling, click on the image

 

[David]

That sounds absolutely perfect. Wow.

As Vraned pointed out, I wasnt getting a spark at #3. I put my strobe lead on the #3 wire and I was getting current from the distributor. I replaced the spark plug and it runs better now. Better, but still not right.

Following Steve's advice, I also checked my secondaries. When I cover the secondary on the front carb with my hand, the idle doesnt move. But on the rear carb it did. I think I need to pull the carb off to gap that throttle. That's going to have to wait for another day.

 

[Peter Coomaraswamy]

Does anyone run with a centrifugal cut-off rotor? Just wondering if this could be the cause of some of my problems?

 

[Stevehose]

I do but I pulled out the spring/guts and use it as a static one. Worth a try.

Does anyone run with a centrifugal cut-off rotor? Just wondering if this could be the cause of some of my problems?

 

[Mike Goble]

Does anyone run with a centrifugal cut-off rotor? Just wondering if this could be the cause of some of my problems?

I have one in my Bav - seems to work just fine up to 6500 rpm or so.

 

[David]

hi david,
yes better, you are on the right way

as promissed, here is a link to a video to hear my iddling, click on the image

I'm curious.What exhaust are you running ?

 

[deQuincey]

I'm curious.What exhaust are you running ?

hi david,
my exhaust is original NOS from germany
regards

 

[David]

According to the STE synchometer instructions, the flow rate at idle for a weber secondary should be between 1.8 and 2.5 kgh at idle and low rpm.

The Weber manual says to adust the secondary throttle valve gap between the outer edge of the valve and the barrel to .05mm (.0002 in.).

Well, I finally gave up and started to rebuild the carbs. I found the secondary throttle adjustment screw but my feeler gage doesn't go down to .002.

 

[Stevehose]

Good deal, I suggest verifying that the sections of the carbs are not warped by putting them on a flat surface and checking for trueness/light underneath, I taped 500 grit sandpaper to our granite counter and wet sanded them flat, while my wife was not there of course...

Well, I finally gave up and started to rebuild the carbs. I found the secondary throttle adjustment screw but my feeler gage doesn't go down to .002.

 

[David]

When we last left this drama, the car wasnt idling well and the rear carb (Carb #2) wanted 3 1/2 turns out on the idle mix screw to be near balanced. Then, after fiddling with the mixture screws, idle speed screws and the timing, it started to diesel.

So fast fwd to today. I pulled the carbs apart.

1. Replaced the throttle shaft bushings with bearings
2. Set the float levels
3. Replaced the gasket in the carb, and the gaskets at the manifold
4. Went to a 55 idle jet (primary and secondary). It had been a 50.
5. Replaced the idle jet rubber o-rings
6. Gapped the secondary throttle at .002

Carb #1: I think this one is a Spanish casting. Using a vacuum gauge on the carb I can get the vacuum and the syncrometer to move smoothly in response to changes to the idle speed screw.

Carb #2: This is an Italian casting. This is the one that wanted 3 1/2 turns out before. Using a vacuum gauge I can get the vacuum to change in response to changes to the idle speed screw, but the synchrometer reading doesn't seem to move much. The reading is very high. North of 20 on the gauge.

It's just as rough as it was before the carb work listed above. Something in the Italian weber just aint right.

 

[David]

Does the vacuum port on the carb get fed just by the primary ? Maybe my secondary is stuck open somehow. That might make sense.

 

[deQuincey]

italy vs. spain ?
ha, ha, ha
how can you tell it is a spanish casting ?

When we last left this drama, the car wasnt idling well and the rear carb (Carb #2) wanted 3 1/2 turns out on the idle mix screw to be near balanced. Then, after fiddling with the mixture screws, idle speed screws and the timing, it started to diesel.

So fast fwd to today. I pulled the carbs apart.

1. Replaced the throttle shaft bushings with bearings
2. Set the float levels
3. Replaced the gasket in the carb, and the gaskets at the manifold
4. Went to a 55 idle jet (primary and secondary). It had been a 50.
5. Replaced the idle jet rubber o-rings
6. Gapped the secondary throttle at .002

Carb #1: I think this one is a Spanish casting. Using a vacuum gauge on the carb I can get the vacuum and the syncrometer to move smoothly in response to changes to the idle speed screw.

Carb #2: This is an Italian casting. This is the one that wanted 3 1/2 turns out before. Using a vacuum gauge I can get the vacuum to change in response to changes to the idle speed screw, but the synchrometer reading doesn't seem to move much. The reading is very high. North of 20 on the gauge.

It's just as rough as it was before the carb work listed above. Something in the Italian weber just aint right.

 

[Arde]

italy vs. spain ?
ha, ha, ha
how can you tell it is a spanish casting ?

He noticed it takes a siesta break ...

 

[deQuincey]

He noticed it takes a siesta break ...

inaccurate ! siesta is a matter of all mediterranean countries, including south of italy
must be something else ...