Weber selection and initial jet tuning

[sweatybetty]

On 4/25/2017 at 2:53 PM, 240260280 said:

Because both throats are controlled by a single idle set screw, sometimes wear or manufacturing variations cause one throat to flow more than the other at idle.  The bypass is used to balance air flow between the two throats.

 

Normally the bypass valves are closed off but if one throat is flowing more air than the other at idle, you can balance the carb by opening the bypass on the throat flowing less air.  This procedure is only needed at idle.

 

FYI: The old way was to drill small holes in the throttle plate to balance (see photo below). (btw the holes solder-up nicely if over-drilled).

 

where is the bypass valve? im not seeing it

[240260280]

the carb above is an early one w/o bypass valve so a small hole was drilled in the brass plate as a bypass to balance air flow at idle.

[blodi]

Got the 165/225 combo back in as well as the .35 exhaust jet.  Removed wideband sensor and re calibrated it.  I'll report back later with results. 

 

 

[blodi]

165/225 with 35 exhaust.....

oddly it's half a point richer than this same combo before. 4 pulls all confirm.  Back to 155/225? 

81617-165225 by blodi, on Flickr

Edited August 16, 2017 by blodi

[240260280]

I guess the calibration must have drifted in past runs... oh well, it looks flat which is good.  Yes please try the 155 again  

 

btw how does the butt dyno sense the rich lean changes?

[blodi]

I'll get the 155's back in tonight.

Butt dyno....not sure I feel a huge difference between each of the setups. I felt more change when changing the choke sizes. 

Honestly, the car starts, runs, drives and pulls well with any of the setups.  It's more about me obsessing over the numbers I guess.

 

 

[blodi]

155/225 35 exhaust...

8-20-17-155225 by blodi, on Flickr

[240260280]

That looks great!  13+/- 0.5 for most of the run. I'll overlay it later today after church.

[240260280]

OK I think you are there.  13 AF +/- 0.5  

 

If you want to go one step further, it will take another fuel jet and air corrector based on the data below. A 160 fuel and 230 air would be as good as it could get.

 

 

  

[blodi]

You've got me tempted. Let me think about it. Might order one last setup.  I'm going to have one large collection of mains/airs/chokes/accel pump jets to get rid of when I'm done. 

 

 

[Patcon]

When I start tuning some triples I might be able to help lighten your load...

[240260280]

I looked at E tubes and F2 are going to be sent. Still deciding on a second set.

We have to tame that lean spike at start too.