Twin Weber Idle Issues

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71rocket
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Twin Weber Idle Issues

Post by 71rocket » Tue Nov 10, 2015 3:32 am

I need some advice with overly rich idle with twin 45dcoes on a holden 308(A9X style).I started a thread here some months ago regarding set-up which is now pretty close thanks to some good advice but I still have one little problem...weak or rich idle.
If I go lean on the idle jets,say 45/1.20 air or 50/1.50 air,idle is weak and stumbles off idle but if I go richer(bigger fuel or smaller air) stumble's gone but fouled plugs at light cruise and spitting fuel at warm-up.
I don't think its a accelerator pump issue though.
ATM Idle jet is 50 with 150 air hole
50 pump jet
45 spill jet
Throttle blades are in right position and engine has 7hg vac @ 1000rpm with 16-34 degrees timing........Any thoughts???

Runit
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Re: Twin Weber Idle Issues

Post by Runit » Tue Nov 10, 2015 10:01 am

Have you tried different model number 45s? I'm thinking that the transfer ports aren't appropriate for your setup.

71rocket
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Re: Twin Weber Idle Issues

Post by 71rocket » Tue Nov 10, 2015 5:27 pm

I have thought that,dcoe 13 only 2 progression holes but I dont know enough about them to start drilling holes

Runit
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Re: Twin Weber Idle Issues

Post by Runit » Wed Nov 11, 2015 9:39 am

Try some 3 port 9s or 152s. 15s+16s are 2 port.

Geoff2
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Re: Twin Weber Idle Issues

Post by Geoff2 » Wed Nov 11, 2015 3:39 pm

Rocket,
Check your PM box.

Runit
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Re: Twin Weber Idle Issues

Post by Runit » Wed Nov 11, 2015 6:24 pm

Scalloped throttle plates might help too.

71rocket
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Re: Twin Weber Idle Issues

Post by 71rocket » Wed Nov 11, 2015 8:25 pm

Runit wrote:Scalloped throttle plates might help too.
I have drilled 1mm holes in blades to get them to close and cover 1st progression hole at idle(maybe wrong move) cos have only 7hg vac @ idle.Thing is,I go bigger on mains and get good performance with good plug colour racing around but then fouls plugs at cruise....different idle jets have only subtle effects :(

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Re: Twin Weber Idle Issues

Post by chimpvalet » Thu Nov 12, 2015 12:45 pm

Suggest you search Yahoo discussion groups for < Sidedraft Central > , hosted by Keith Franck. He's been working up a very technical approach to sorting DCOE issues for years and has developed a number of components for improved behaviour. Lots of techniques also expressed for dealing with the transition gaps inherent in most DCOE applications.
Steve

71rocket
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Re: Twin Weber Idle Issues

Post by 71rocket » Thu Nov 12, 2015 4:16 pm

Yes ,I was reading some of Keith Francks info yesterday and it has answered some of my questions,most stuff I've found just repeats the same old baseline setting thing but not 'how and why'.Looks like I'll be making some big changes with fuel levels and main/ac selection...and hopefully stop chasing my tail.

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Re: Twin Weber Idle Issues

Post by Runit » Fri Nov 13, 2015 10:10 am

This morning I remembered working on a Weber that was one of a pair on a sidedraft adapter for a SB Chevy. The customer wanted new low speed jets installed which I had to make. I thought I jotted the calibration down but I can't find the notes. I do I remember seeking guidance from Mike Pierce at Pierce Manifolds if that helps.

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