engine and drivetrain Weber 38/38 Tuning

[roadhog0]

1 hour ago, mattio523 said:

 

perfect, just got two f66 emulsion tubes and a 250 needle off there. thanks!

 

I've been known to get them from Carquest or somewhere like that (worldpac distributor). If it were me, I would probably drop your idles as well, but they're not that far off. Just depends on your car really.

[theNomad]

I fiddled with the setup today after having the idle drop way too low after highway running. Its an odd process like every time I tune for best lean idle it doesnt react the same. Now im set at 1/2 turn on each lean idle screw, and 1/4 turn on idle screw. This gives an idle of around 1200 rpm. I may have to go lower in idle jet and see what it does. Ill get some driving in tonight and see if itll stay consistent on idle after higher rpmsother than high idle it feels great, nice power, smooth running. I need an exhaust though as mine leaks t the header and its blowing glass from the muffler.

[4wheelforay]

On November 2, 2014 at 0:58 PM, Tombonetoo said:

One way that I found to improve the lean-out in the transition phase was to change from an F50 to F66 emulsion tubes.   I experimented with several emulsion tubes on my 38/38 (not a cheap proposition), and the F66 with its lower drilled holes eliminated the transition phase lean out as measured with an WBO2 sensor.   Final configuration:

 

Mains                               155  (stock 145)

Idles                                   55  (stock 45)

Air Correction                   165 (stock 185)

E-Tubes                            F66 (stock F50)

 

We are at 600 feet above sea level here in Fort Worth.    As you can see I took a different route in dialing this carb.   I should note that the 38/38 I am running has a 250 Needle Valve (not a 200 as noted by the ealier poster), 60 Pump Jet (slightly smaller than stock size) and 35 Pump Bleed (slightly larger size).  

 

I have a completely stock 69 2002 with a newly installed Weber 38. I fiddled with the idle mixture screws and kept them within the recommended settings on the redline weber tuning page. I do not believe I have the idle (not idle mixture) screw in too far. It was running great for a while, pulling hard, idling well, no hesitation between shifts once warmed up. I drove it 200+ miles with this "stock" carb setup. The other day I was driving it and in second gear the car developed a disconcerting hesitation at about 3k RPM. It was almost a violent cut in power. It was 95+ degrees and by far the hottest day I had driven the car with the new carb. I pulled the plugs today to see if I could get a read off of them, the pictures are below, it looks like the car might be running rich? I quoted Tombonetoo because we are at similar elevations and he seems to have the most stock engine on this thread; should try to copy his setup as a "jumping-off" point?

 

I am not sure what the carb is currently jetted at, the only thing I can see is "170" on the top of what I believe to be the air correctors. The only thing I noticed that was off before the cars recent troubles was that it would spit quite a bit of water while running, especially warming up. 

 

Thanks for the help!

 

Plugs 4-3

Plugs 2-1

Edited June 29, 2016 by 4wheelforay

[Zorac]

the plugs look a bit rich, but not bad (the left one looks like it might be wet, then it might be fouled).  ive had my 38/38 foul plugs, which might do whats happening to you (i would expect them to be black then though)?  when mine fouled, it was hard starting and running on 3 cylinders when cold.  put new plugs in and it was off like nothing happened.

[76ohtwo]

My engine was just put in the car and seemed to be running well when the car wasn't moving when the timing was being set, but according to the shop they took it out and it was bogging and felt like it had no power. (Fresh rebuilt engine, shouldn't have no power).

 

My set up is a 90mm 10.5:1 compression pistons, 292 cam, E21 head, shorty header.

 

The carb is a 38/38 with the following specs:

 

Mains: 140

Airs: 180

Idles: 55

Emulsion: F66

Needle: 250

 

Any ideas as to what might be happening? Could it have to do with the carb setup? I thought it would run close to well with that setup and not need a ton of adjustment. 

 

I'm hoping that the problem will solve itself with some fresh gas - the gas in the tank is kinda old.

 

Thanks

 

UPDATE: it was a bad ignitor - don't forget to run resistors everyone!

Edited August 9, 2016 by mattio523
update

[76ohtwo]

Hi everyone!

 

Hate to revive this thread (again) but oh well. Going to do some tuning on the 02 this week and was wondering if anyone had any tips for swapping jets out. Should I take the carb off the car and swap them out that way, or is it easier (as it seems in my head) to change them while the carb is on the car?

 

Thanks!

[Dudeland]

I just put in a new carb, the old 32/36 had a shaft bent so bad I couldn't install the bearing kit.  I would leave it on the car, unless it needs to be rebuilt.  They are kinda designed to be able to change out the jets on the car.  

 

[bento]

Yep, leave the carb in place. Everything is accessible and you'll be able to get it back up and running in about 5 minutes to try each jetting change.

[Zorac]

since the topic has been bumped from the dead...

 

i have always had a bit of an issue with transition which closely corresponds with cursing on the highway.

 

currently:

idles 50

mains 150

air 215

emulsion tube f50

 

for afr, i run a bit rich around town (12 to 12.5) and bit rich at wot (12ish) but about 14 on the highway and a if there is a slight load around 15.  i was playing with emulsion tubes (i read more holes lower down should encourage transition sooner).  f7 and f66 were worse, but then I recently tried f24 and the whole thing went to crap.  running 10 to 11 around town with a 40 idle jet (changing idle jets don't make any difference, still running the 150 main and 215 air).  not fully understanding what happening, i think its essentially has the main running most of the time now, do i need to either make the main smaller for less fuel, or smaller air to limit the flow through the circuit? or is a f24 just not right for what im trying to do?

[kbmb02]

10 minutes ago, Zorac said:

currently:

idles 50

mains 150

air 215

emulsion tube f50

 

 

I can't speak to your issue(s) overall.

 

However, it seems to me that's a large (*too large) difference between main and air corrector sizes (*the guru at Weber would take issue with that setup). In my experience, going larger with air correctors leans out the mid-range and top end (say, 5 - 7k RPM).

 

Suggest: make one change at a time, test and change again same day / weather conditions (density altitude is a factor, so what works when it's 60°F will behave differently at 95°F with varying amount of moisture in the air).

 

[Zorac]

54 minutes ago, kbmb02 said:

 

I can't speak to your issue(s) overall.

 

However, it seems to me that's a large (*too large) difference between main and air corrector sizes (*the guru at Weber would take issue with that setup). In my experience, going larger with air correctors leans out the mid-range and top end (say, 5 - 7k RPM).

 

Suggest: make one change at a time, test and change again same day / weather conditions (density altitude is a factor, so what works when it's 60°F will behave differently at 95°F with varying amount of moisture in the air).

 

 

its a bit of a balance, if i go smaller on the air, it helps on the transition but goes too rich on wot.  if i go smaller on the main to make up for it, then the transition goes way to lean.  i started off with cd's recommendations and worked up from there.  when i was jetting i actually went the other way, started much smaller (if i remember right, i started  with 145 mains and 185 air, have it written down in the garage), then worked up.  air was the last thing i adjusted before i started messing with the emulsion tubes.  weather does make a noticeable difference as well.

[76ohtwo]

Did a little rejetting this morning, then took the car for a drive.

 

Mains: 140 150

Airs: 180 190

Idles: 55

Emulsion: F66

Needle: 250

 

Car does much better in the top end (above 4000 RPM) than with the 140s and 180s. Used to definitely feel like it was running out of breath up there and now it pulls all the way through the range. Very happy with the results.

[rstclark]

Despite the title saying 38/38. I think the current discussion is about a 32/36 on a fairly stock motor Yes ?

If so I'll offer this set up on my 32:36

motor is fresh 9.5 compression 284 cam and shorty header 123 tune distributor

pI 65. Pm. 150 PAC 170

si 55 am 145 sac 160

stock emulsion tubes ?  Don't know what they are.

Needle valve is stock.  I believe it's 200

Good idle no stumble or transition issues

pulls to redline

tail pipe is black. No air ratio readings

but I'm more comfortable with a little rich than a little lean.

Hope this helps

[xr4tic]

As far as I know, this is a 38/38 thread, and I'd like to keep it that way if possible, lots of good info in here that mostly applies to the 38.

[wtinker]

On 5/28/2016 at 8:06 PM, wtinker said:

I had the same experience recently. Took mine to the Vintage is Nashville NC.  On the way back idle got very squirrely. Coming off highway cruse pegged ATF lean and stalled everyime.

 

Now idle is super lean and rough.  I will play with it tonight to see if it will dial back in.

 

Next will be to order/change Em Tubes to the F66 to see if it can fixe the lean stumble coming off idles.

 

 

Ok, well seems like I only get to this around this at this time of year!  Thus I reviewed the 7 pages on the thread, summarized what you guys did,

ordered up some parts and went at it.

 

Note: Since last posted we have rebuild the M10.   The package is now 10:1, 292 IE Cam/Rockers, shorty header and the 38/38.

 

So here we go:

                             Idles      Airs     Mains   E-Tubes

As Rec'vd:             50         185      140        F50                Ran real rich (9-12 ATF) at cruse,

                                                                                           worse on hard accel and real lean stumble on when easing back into throttle

 

5/16/2017a:           50         185      135        F66                14 ATF on hard accel and MAJOR leaning on off throttle

 

5/17/2017b:           50         170      135        F66                 Cruses at 14-15,   13-14 on medium accel, 12 on max axcel,  still 18+ lean stumble 

                                                                                             light pedal

 

I need to order some smaller Airs so see what that does.   I fell like I aught to stay with the F66 since the majority of you all did good with it.

 

I'll welcome any suggestions to fix the lean stumble......