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Discussion Starter #1
I have had tripple 40dcoe on my 240 for years with no probs. I now have them on an L28/e31 engine. It has a an aftermarket cam but I don't know the specs.
I can not get my idle mixture lean enough to pass air care. It breezes the dyno test but bombs the idle test.
I am not getting the performance that I should.
I have contacted an out fit called Pierce Manifolds who have been very helpfull. They seggested that I go to a 36mm Aux venturi, they also seggested that the 40s are as they put "borderline" for my application. I wish to order some parts from them but being that I am in Canada it's going to cost quite a bit. What I would like is some input as to jet sizes etc to improve performance so I can keep my expenses down.
Here are the specs for the carbs as they are now.
Main Venturi 28mm
Aux Venturi 38mm
Main jet 120
idle jet 45 F9
Emulsion tube 170
Any input or advice on jets sizes I should try etc would be valued I cant get any of this stuff where I live anymore.
 

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Not really a guru but I'll try. I don't understand your 'aux venturi' numbers. All the books I have refer to aux venturi by 3.5, 4.0, 4.5 etc. and recommended aux size for most Z's would be 4.5 (flowing up to 500 cc's per cylinder). If dyno readings are good for everything except idle, then I would think that you need to work with the idle jet and bleed #s although yours sound fairly low enough now. Are you saying that you can't turn the idle mix screws in enough to get a good idle and pass emissions. If so then it would seem your only choice would be to change idle jets, or perhaps go back over float settings and also make sure the accelerator pumps aren't leaking fuel.
A couple of good books:
'Weber Carburetors' - Pat Braden, HP books, ISBN 0895863774
'How To Build and Power Tune Weber & Dellorto DCOE & DHLA Carburetors' - Des Hammill, ISBN 1901295648
 

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Discussion Starter #3
Thanx for the response

I am fairly sure the problem is idle jets and the aux venturi being too small. I used to know people here who had lots of Parts but no more ! As a result finding the right jets is a pain. It's hard to do when you don't have a huge box of various jet sizes and are faced with ordering everything. I figured the best way to star would be to find out the sizes others are using on an L28. I will check the pumps though, hadn't thought of that.
 
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