engine and drivetrain Weber 38/38 Tuning

[76ohtwo]

I didn't leave it stock, Interestingly they have 135 as the mains and 185 as the air correction. Each moves towards lean.

Mine, on stock internals is currently:

 

Yeah, when it's all done I'm going to test her on the dyno to see where I'm at in terms of AFR and where to go from there. But I figure that's a good baseline, I think IE knows what they're doing.

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[theNomad]

Certainly, report back! I don't have an O2 sensor.

Edited May 28, 2016 by theNomad

[theNomad]

Got her fired up this morning thanks to arminyak giving me some valve eccentric nuts. Made it to Bimmerfest on her maiden voyage. Set idle to 800 perfectly, nce smooth idle. I believe a slight exhaust leak causes popping on deceleration. Ran smoothly at 65-70mph 3500 - 4000 rpm on the freeway. 

After the freeway run though the idle dropped to around 200 and it was sputtering and needed feathering constantly. Just not happy at idle.

After a few stalls it cleaned up its act and idled as needed so not sure why the constant change. I'll be fiddling with timing, and carb tuning over the next few days.

[wtinker]

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.

 

Edited May 29, 2016 by wtinker
Typo

[76ohtwo]

I've just checked my carb and it looks like my specs are as follows:

 

Mains: 140

Air Correctors: 180

Idle: 55

I couldn't figure out how to remove the emulsion tubes, jet needle, or pump jet so I did not check those. It seems the carb is set up to run slightly richer than previously expected.

 

I would really like to be able to check if the needle is a 250, any tips on this would be appreciated. 

 

[roadhog0]

8 hours ago, mattio523 said:

I've just checked my carb and it looks like my specs are as follows:

 

Mains: 140

Air Correctors: 180

Idle: 55

I couldn't figure out how to remove the emulsion tubes, jet needle, or pump jet so I did not check those. It seems the carb is set up to run slightly richer than previously expected.

 

I would really like to be able to check if the needle is a 250, any tips on this would be appreciated. 

 

 

I believe it will say on it. As far as removing emulsion tubes, I've had good luck with sticking a screwdriver in them and pulling up. I know, real scientific.... Since last time I commented I have upjetted to a 50 idle which helped my cruise AFR but I now idle at 13. Arguably that helps with keeping the motor cool... Still have a tip in past cruise lean out, so a bigger emulsion tube probably wouldnt hurt.

[bento]

8 hours ago, mattio523 said:

I've just checked my carb and it looks like my specs are as follows:

 

Mains: 140

Air Correctors: 180

Idle: 55

I couldn't figure out how to remove the emulsion tubes, jet needle, or pump jet so I did not check those. It seems the carb is set up to run slightly richer than previously expected.

 

I would really like to be able to check if the needle is a 250, any tips on this would be appreciated. 

 

Emulsion tubes are under the air correctors. I think I fished mine out with a pick after removing the air correctors.

 

The needle valve just unscrews from the seat in the carb cover.  I don't recall whether they're labeled. You didn't mention any details on your motor. Is it stock? If so, the 200 (stock) needle valve is fine. If not, you'll know when you need it. It has no effect on how your engine runs unless you aren't getting enough fuel in the float bowl at high rpm/high load.

 

Edit:Fixed description of needle valve location. 

Edited June 19, 2016 by bento
Fixed needle valve location description.

['76mintgrün'02]

Emulsion tubes are soft (thin) brass, so be gentle with them.  I looked closely at mine, when I had things apart, and someone had taken them out with a pocket knife, or something.  The opening at the top was chewed up.  I honed that back to smooth, with a conically shaped dremel stone... very lightly, until I did not feel the resistance of the burrs.  That resistance I felt was an illustration of the 'drag' they would cause to the air flow and things should flow smoooother now.

 

I had a pair of tubes which were frozen in place.  If the carb has sat around with moisture in it, or ethanol flavored gasoline, there can be corrosion issues between the brass tubes and the aluminum body.  At least that is my theory.  The 'glue' in mine was a sort of white powdery substance, which seemed like aluminum oxide.  There is minor pitting in the brass as well, which is probably where the zinc 'washed out of' the brass, forming 'glue'.

 

I put a little PB in each tube and let them sit.  Then whittled down a larger sized bamboo skewer, to just fit inside the tubes.  Once inside, I gave it some side pressure and pulled up.  The bamboo grips on the holes in the tube and pulls pretty well.  Remember, the tubes are thin and soft.  I am pretty sure the tip indexes the bottom of the hole in the body, so they shouldn't bend, but do be careful with them.  Once out, the pointy tip of the skewer makes a good scrubber, to clean them up.  I liked my skewer-puller so much I gave it a rubber handle and added it to the tool kit.  VW washer hose rubber, of course.

 

As I mentioned, these were stuck, so I used a small piece of soft aluminum to tap on them and help break them free, before pulling them out.  That little dental brush made a nice scrubber.
Tom

 

[theNomad]

In this photo you see the top center pump jet hole, the two air corrector holes on the sides, the emulsion tubes drop into these passages. Everything comes out with a flathead screwdriver.

 

I used a paperclip with a tiny section bent to a right angle to reach into the emulsion tube, grab through a hole and give a strong pull up. One was a lot harder to get out than the other. These are F50 but I replaced them with F66.

 

 

At the bottom of the bowl is the large power valve and the two small main jets.

 

The needle valve and seat is attached to the cover with the floats and is marked with a 200 if it is original and (from what I've read) when you buy a new one it'll be a 250.

 

I tried to put as many photos as I could on my blog.

[vinceg14]

Nice assist Nomad. 

[76ohtwo]

On 6/19/2016 at 0:58 AM, bento said:

Emulsion tubes are under the air correctors. I think I fished mine out with a pick after removing the air correctors.

 

The needle valve just unscrews from the seat in the carb cover.  I don't recall whether they're labeled. You didn't mention any details on your motor. Is it stock? If so, the 200 (stock) needle valve is fine. If not, you'll know when you need it. It has no effect on how your engine runs unless you aren't getting enough fuel in the float bowl at high rpm/high load.

 

Edit:Fixed description of needle valve location. 

My engine has 10.5:1 compression and a 292 cam, which is why I want to make sure I have the 250. I can't figure out how to take it off. Just unscrew by hand? 

[theNomad]

Its a nut so use small spanner or a socket.

[76ohtwo]

Alright, was able to check everything today.

 

Mains: 140

Airs: 180

Idles: 55

Emulsion: F50

Needle: 200

 

Guess I am going to order at least a 250 needle and probably F66 emulsion tubes. Where does everyone order this type of thing? Thanks. 

[theNomad]

I ordered from Carbs Unlimited just fine.

 

http://www.carburetion.com/Weber/weberparts2.asp

[76ohtwo]

15 minutes ago, theNomad said:

I ordered from Carbs Unlimited just fine.

 

http://www.carburetion.com/Weber/weberparts2.asp

 

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