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Author Topic: Weber carb idle air jet mod  (Read 6118 times)

Offline a2ndopinion

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Weber carb idle air jet mod
« on: Feb 14, 2010, 07:55:21 am »
After spending weeks on jetting and getting nowhere, only to find out that the catalytic converter was coming apart and plugging the exhaust, I finally got the header and 2.25" exhaust on, so can get to the nitty-gritty on carb tuning.
With the highly polished, knife-edged and air-foiled carb, I'm having one hell of a time getting the idle/part throttle/cruise jetting correct. I stopped 7 (seven) times during my 300 mile drive on Friday to swap jets - idle, main, air correctors and E-tubes. Reducing the idle jet size to get it lean enough to part throttle cruise at just under stoichiometric causes it to not idle and the mixture screw is way out, but this way I can run a larger main jet so the mixture stays closer to stoichiometric all of the time. The problem is that it won't idle worth a damn. I came across an article about the fairly new "Mighty Demon" carbs by Barry Grant, used on larger V8s, and figured there had to be a way to adapt one of their options to the Weber 32/36.
This is what I came up with.

1) Take the carb off and unscrew the lid...

2) ...then remove the lid

3) Carefully clamp the carb in a soft-jawed vise. This is the idle air bleed - between the venturi and the bowl.

4) Remove the idle jet

5) Drill out the idle air hole with a 5/32 bit - all of the way into the idle jet passage

6) The remains of the air bleed

7) Idle air hole with the bleed removed

8) Get a M5x8 tap...

9) ...and tap the hole

10) The idle air bleed hole is now tapped for...

11) ...what is now an idle air jet! That was a main jet. The air bleed hole was 1.70mm, which would be a 170 jet.

12) The next issue is that the lid doesn't fit

13) So grab your Dremel (die grinder, whatever) and grind the gap in the lid where the jet resides wider and deeper

14) Now the lid gasket doesn't fit...

15) ...so grab your hollow punch set...

16) ...find the one that fits the jet...

17) ...and punch the gasket

18) Now the gasket fits

Viola! You now have an idle jet in your Weber carb for ultra-fine tuning!

Now onto the next project...
« Last Edit: Feb 15, 2010, 03:30:52 am by a2ndopinion »
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Offline hayabusa

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Re: Weber carb idle air jet mod
« Reply #1 on: Mar 20, 2010, 10:30:58 am »
nice. very nice ;)
Chop cut rebuild. Stock sucks FOR MOST CARS.

Offline 93cc

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Re: Weber carb idle air jet mod
« Reply #2 on: Jan 02, 2011, 11:04:05 pm »
now that is what I call a mod...  how did it work out?