40 DCOE Synchronization, HELP!!

[Hans]

The spindle nuts are locked by tabs, not torque.

One more time, soft mounts? Carb springs?

 

Spray quick start or carb cleaner around manifold.

[NickVyse]

don't forget to check for vacuum leaks at the other end of the servo hose, the one way valve and around the servo. My 1600-2 ran like a pig when I bought it - the previous owner had misassembled the remote servo so #4 runner was just sucking air.

 

I'd temporarily plug it to rule any problems out.

Edited June 2, 2023 by NickVyse

[Preyupy]

If carburetor #1 is showing a HIGHER number on the syncrometer than the other 2 carburetors you are flowing MORE air THROUGH the carburetor.  An air leak at the manifold or even the brake booster would cause LESS air to go through the carb not more.  If the other 2 carbs are running correctly you have a problem with the linkage and the #1 carb is open too much. What type of linkage are you using between the carbs?  

[Son of Marty]

Have you removed 2 of the 3 idle stop screws?

[Hans]

On 6/1/2023 at 2:26 PM, Preyupy said:

If you are getting a different reading between the 2 throats of the same carburetor someone has bent the throttle shaft in the process of installing the linkage arm.  The only way to fix it is to bend it back.  People like to put a wrench on the nut on one side of the carburetor while they tighten the one on the other side. You basically need to reverse this process to get them even again.  It will take some trial and error.  

Errrr.........what if it turns out to be something else....?

[Chris_B]

Check the position of your "butterflies" in the progression hole viewing port. Your throttle plates should be lined up under the first progression hole, if all adjusted correctly. If not, then you have a problem with in carb or carb to carb alignment.

Edited June 3, 2023 by Chris_B

[TobyB]

15 hours ago, Hans said:

Errrr.........what if it turns out to be something else....?

 

well, that's the 'joy' of troubleshooting, isn't it?  The thing is, there are a thousand little 

'wtf is that?' things that can go wrong, and to spot them, the car's gotta be sitting right in

front of you (or even on top of you) and staring you in the face.

And there are lots of clues that aren't visual, too, like the way it drops back to idle, the

way the shafts feel when moving, what happens when you block each

throat in succession, yadda et yadda de yadda...

 

And then there's the thing you haven't seen before that, once you see it, you say-

'well, duh, obviously THAT would do it' but it's nothing that would occur to mention

over the interwebs.

 

Since Hal's not all over this thread, there's not a whole lot we can do but say

'this is what's gotten me in the past, and here's how I've found it'

and leave him to it!  Since he's the one with the car in his face...

 

t

 

[Hans]

2 hours ago, TobyB said:

 

well, that's the 'joy' of troubleshooting, isn't it?  The thing is, there are a thousand little 

'wtf is that?' things that can go wrong, and to spot them, the car's gotta be sitting right in

front of you (or even on top of you) and staring you in the face.

And there are lots of clues that aren't visual, too, like the way it drops back to idle, the

way the shafts feel when moving, what happens when you block each

throat in succession, yadda et yadda de yadda...

 

And then there's the thing you haven't seen before that, once you see it, you say-

'well, duh, obviously THAT would do it' but it's nothing that would occur to mention

over the interwebs.

 

Since Hal's not all over this thread, there's not a whole lot we can do but say

'this is what's gotten me in the past, and here's how I've found it'

and leave him to it!  Since he's the one with the car in his face...

 

t

 

t:

Agreed, but before I start twisting my spindle (so to speak), I 'd want to be sure I'd eliminated everything else. Hard to back up on that manoeuver.

 

As I understand it, he swapped #1 carb and got same results. That would suggest it's perhaps not the #1 carb. 

[John76]

48 minutes ago, Hans said:

That would suggest it's perhaps not the #1 carb. 

My thought too.

What are the chances of two DCOEs producing identical symptoms only on the first manifold?

 

[Son of Marty]

17 minutes ago, John76 said:

My thought too.

What are the chances of two DCOEs producing identical symptoms only on the first manifold?

 

<0.

[visionaut]

That’s what I was saying. 2 carbs with identical calibrations, swapped into position 1 (cylinders 1&2 ) both can pull 10s.  The untouched two rear carbs for cylinders 3-4 and 5-6 both pull only 6s.

 

I’d be figuring why the rear two aren’t flowing 10s — but I guess you could try getting the carb in position 1 to flow 6s.

 

All cylinders look great at the head and the bottom end has no cyl 1&2 versus 3-6 variations.

 

He verified the progression holes.

 

manifold or booster leaks, binding or uneven linkage, or reverse-twisted spinlidges…

Edited June 3, 2023 by visionaut

[ray_]

I believe Hal is at Mid-Am. But I don't know what he drove to there.

 

[TobyB]

Bastard.  Now I really hate him*.

 

So maybe there's an air leak on the back 2 carbs?  That's the same?  That's waaaayyyy odd.

 

The thingus is, it should be easy to idle down any particular carb to no airflow, and if it's

not, then SOMETHING is up with that position.  Usually linkage, if it tracks.

But that should be super obvious...

I have found that DCOEs are very physical beasts- as in, I always had to manipulate them 

to really understand what they were doing.  Looking didn't tell the whole story.

Twisting screws and bolts and jets and stuff was far more informative... and educational...

 

t

*just kidding.  Horribly jelly, though.

[halboyles]

I really want to thank everyone for the great ideas in troubleshooting this very odd problem.  As @ray_ mentioned,  Mid-America 02 Fest consumed much of my time last week and, thus,  I have had no chance to test any theories because, paraphrasing @TobyB, I didn't "have the car in my face!"

 

It will take me a while to catch up on orders and correspondence, but I will once again have the car in my face to check out some of the possibilities proposed.  As I mentioned in the original post, I had already tried many of the proposed solutions before writing up the request for help, but I will start over with the basic setup before proceeding with some of the other more exotic possibilities.

 

While down in Eureka Springs I did check with some DCOE pros and received suggestions ranging from "It's the cam!" to "Impossible!"  Terry Sayther very sagely suggested I take to heart Sherlock Holmes famous adage that "when you have eliminated the impossible, whatever remains, however improbable, must be the truth."

 

Thank you everyone again and I'll inform the group when I have resolved the "improbable truth".