HELP please! DCOE’s stumbling (leaning out) at ‘tip in’...

[Hans]

You do have plastic floats, right?

Edited May 14, 2021 by Hans
Clarity

[sam1904]

53 minutes ago, Hans said:

You do have plastic floats, right?

Indeed I do! New 151 carbs. 

[Dudeland]

I have heard a lot of people say on this forum that 98% of "carb problems" are actually ignition problems.   I haven't gone through every post, so excuse me if I am misinformed. 

 

Food for thought. 

[Chris_B]

Wait. I thought it was 98% of ignition problems are carb problems.

[Hans]

12 hours ago, sam1904 said:

Thank you for all the comments which I need to read and digest. Between waiting on some different tubes to arrive and then spending three days searching for gas so I could drive the damn thing it's been a while since I gave an update so while I digest the content here is a quick update on the last few days.

 

I changed to F16 tubes as suggested by a couple and worked on fuel level. I am still struggling (or over thinking it) as measured with the tip of my calipers I am now sitting at around 28mm fuel level but this required going to 10mm (not 12mm) float clearance at center. To get in the 27 range will move me to 8-9mm which I will try later.

 

With the new F16 tubes, jetting as shown at start of thread and idle screws out 2 turns my A/F at idle is close to / slightly above 11:1. I still have the stumble but it is slightly better and can now be (mostly) driven around. I also have Chris Joyner here in town and as I have a couple of other things I have worked on I would like him to cast an experienced eye over I will see what his highly calibrated ear makes of this next Thursday!

 

Will review the thread above and get to 27mm and update further.

 

Thanks

Sam

It seems odd you would need to go 8mm. How are you measuring depth?

[Chris_B]

It is pointless to be concerned with precise float measurements except to the extent they affect your fuel level... 

 

11:1 is pretty darn rich. You should be swapping idle jets, not E-tubes. 

[2002Scoob]

Make sure you're also adjusting float drop as well. If you don't, and you're running a higher than normal fuel pressure you can trigger a whole variety of symptoms as well due to surges of fuel in the bowl, floats binding under certain driving conditions, etc etc. I run around 1.8. I'm convinced on a mild motor like yours and mine you don't need more than 2. And yes, cranking it up, at least on my car, does affect richness. Dunno why. 

 

and yah... 11:1 idle is waaay too rich, you're just masking the issue of needing a richer progression circuit. 

 

Up your Idle jet so you can back off your adjustment screws. 

 

 I tend to aim for 13, but AFR at idle on the gauge tends to flutter around 12.5-13.5, and it might occasionally spike high or low with an errant 11.5 or a 14.5-which I chalk up to 60's technology. 

 

When I was getting deep in the weeds, I scoped out a business park that was quiet after work and on weekends, with a shaded parking lot next to a nearby highway and exit and entrance ramps that could let me do runs and get back to my starting place.

 

That way I could swap jetting, test it around the park without too many people around to judge me, and make adjustments if I had to. And if all seemed good, I could then take it on the highway to do higher RPM/ WOT pulls. The entrance and exit ramps also served well to test the affects of cornering loads.

Edited May 15, 2021 by 2002Scoob

[2002Scoob]

One last question that I don't think I saw addressed.... 

 

What size chokes are you running? On a stock motor, 32's is all you probably need, and the restriction might help ease some of your tuning woes. 

 

FWIW.... I never had the tip-in problem TILL I went from 32's to 34's after building a new bottom end with 9.5:1 compression and a 292 cam. I even ran that motor for a while with the 32's, and didnt have the issue. 

 

It was only after I went to 34's hoping to let it breathe better I started to experience that lean-tip in, and via the butt-dyno it indeed pulls harder and better in most scenarios, the 32's were probably a better choice for drivability. 

Edited May 15, 2021 by 2002Scoob

[Carlos_M]

On 5/14/2021 at 10:11 AM, sam1904 said:

Thank you for all the comments which I need to read and digest. Between waiting on some different tubes to arrive and then spending three days searching for gas so I could drive the damn thing it's been a while since I gave an update so while I digest the content here is a quick update on the last few days.

 

I changed to F16 tubes as suggested by a couple and worked on fuel level. I am still struggling (or over thinking it) as measured with the tip of my calipers I am now sitting at around 28mm fuel level but this required going to 10mm (not 12mm) float clearance at center. To get in the 27 range will move me to 8-9mm which I will try later.

 

With the new F16 tubes, jetting as shown at start of thread and idle screws out 2 turns my A/F at idle is close to / slightly above 11:1. I still have the stumble but it is slightly better and can now be (mostly) driven around. I also have Chris Joyner here in town and as I have a couple of other things I have worked on I would like him to cast an experienced eye over I will see what his highly calibrated ear makes of this next Thursday!

 

Will review the thread above and get to 27mm and update further.

 

Thanks

Sam

Sam1904 -

  Do you have an update on your situation?  I'm running into the same issue, which is a new development after I was forced to replace my manifold.  While I was at it, I replace my linkage, moved the fuel filter to after the mechanical fuel pump; and it's been a complete mess.  I seem to balance at idle but then take it for a test drive and it bogs exactly as you explained at the top.  The redline rep had me check my idle jets... 3 x 55, 1 x 45 oops... I'd love to hear how you're sorted it.  Oh and this is after 2 years of driving with the new carbs, perfectly tuned and zero problems.  

 

Thanks!

  

[Chris_B]

The first question that comes to mind is what, if anything, else did you change- no matter how inconsequential. Why were you forced to replace your manifold, and how does the new manifold differ from the old?

[Carlos_M]

51 minutes ago, Chris_B said:

The first question that comes to mind is what, if anything, else did you change- no matter how inconsequential. Why were you forced to replace your manifold, and how does the new manifold differ from the old?

?  well.. it all started with what I thought was a bad fan belt so I asked my mechanic to put one aside and I would grab it on my way through town.  The mechanics discovered that I had an air leak from a broken manifold bolt, lower below the water divider. 

 

I replace the broken bolt and did not realize that I needed smaller head 8m x 1.25 nuts an I eventually broke the ear off of the manifold.  Called around, couldn't source 1 manifold of the redline kit that IE sells so I bought a 1 piece warneford.  Those are a lot easier to install than the redline ones.  I installed new linkage and seemed to get the car tuned  very nicely but I noticed a slight bog in 5th gear, 3500 RPM while cruising.  Thinking it would be an easy adjustment I proceeded to goober up everything and was luck to get home in 4th gear at 4000 RPM.  I tried for days to set it back up to no avail.  I finally connected with a redline rep who sourced a replacement for my broken manifold and proceeded to  return the car to it's previous state.  Tonight is when I noticed the idle jet problem, which hadn't been a problem until I looked for it... Ha!  The only difference now is that I have a K&N fuel filter just forward of the firewall, replacing the standard bosch.  I tried the K&N after the fuel pump, before the carbs but now I'm just trying to get back to 2 weeks ago when things were great!  I've also tried 1 1/2 turns out on the mixture screw per redline rep's guidance and the car pops all over the place.  Rep said when I change out the idle jets to 60's, 1 1/2 turns out should be perfect...

 

I also noticed the venturi's were all lose and rattling around so I adjusted the screw without checking to see if they were still in the proper configuration.  I'll check that next week...

Edited May 28, 2021 by Carlos_M

[Chris_B]

Would you pls restate your problem? It is kind of hard from your description to determine what symptoms your are having, Is it anything other than the bog at 3500 you described?

[Carlos_M]

14 minutes ago, Chris_B said:

Would you pls restate your problem? It is kind of hard from your description to determine what symptoms your are having, Is it anything other than the bog at 3500 you described?

exact same as sam1904.  Idles fine then when I attempt to drive, 1st gear bogs down, super lean at 2500, 2nd gear not much better but if I can feather the accelerator to above 3500 RPM then I can get to where I need to get but when RPM drop down and I gas, slightly or even step on it... nothing - no power, nothing.  I can then get off accelerator and feather a bit to get some gas into into the system.  I've got both carbs balance before I begin adjustments and airflow meter to make final adjustments.

[Chris_B]

This problem sounds kind of familiar (most DCOE installs on 02 motors). So, the only thing you changed was your intake manifold (not a trivial change). Do you have a wideband AFM? If so, what are your readings at idle? In any event, I suggest you crank open your idle mixture screws to the point where your motor almost dies (and open your idle speed screws a bit to keep your motor running at idle..). Then go for a ride and see if your get better performance at those "bog" points.

[Carlos_M]

I do not have an afm but will look into it. Thanks for the input. When I receive the new idle jets, and they are all the same, I will do as suggested. Next week sometime. Thanks for taking the time to help.