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  #41 (permalink)  
Old 09-15-2009, 12:15 AM
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Default More testing, more sollutions

After alot of testing, this is what has come up;

I've done all of the above, even run NGK 7 plugs now.

The engine run really well above 4000 (up to somewhere... How long can it be stretched?).

It is still hesitating/ grumbling between 2000 and 4000 after braking through a corner and then accelerating. This is because of excess fuel.

Although shifting into 2. gives the punch, I'm convinced that a leaner bottom end will make the car faster as the time used for downshift + upshift will be larger than the time used for accelerate in 3. from 3000 and up...

What will be tried first is:
Use a smaller main fuel jet (from 165 to 145) and a smaller air jet (from 220 to 200). In theory, according to Mr. John Passini (if I read his words correct...?), this will make a leaner low end while keeping the upper end as is. Sounds smart, or?

The 2. choice is to follow Eljaro,Interesting Weber jetting, and use the F15 emultion tubes ("Tubes with bigger diameter for engines with strong vibration or high compression" and "Leaner low end and throttle response")

Runes
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  #42 (permalink)  
Old 09-28-2009, 02:04 PM
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Hello everyone.

Does any one have any f-19 and/or f-57 tube`s for sale? My carburator is DCOE weber.
If so, please send me a PM or e-mail me at christoffer_johnsen@hotmail.com

In advance, thanks

Tom Johnsen, Norway
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  #43 (permalink)  
Old 09-29-2009, 01:28 AM
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Rune,

Your two next trial procedures both have merit and both are worth trying even if you are happy with the first outcome.

Back-to-back testing with a stopwatch and/or dragstrip acceleration test with a wideband O2 sensor fitted is also worth the effort.
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  #44 (permalink)  
Old 01-21-2010, 05:35 AM
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Hi there

It seems there is alot of experience for this chat.
I would just like to solve the problem i am having without buying 20 different e tubes.
I have a chevy 350 with four weber 40 DCOE's and the engine has a flat spot between 1500 and 2000 rpm. then it coughs and splutters when just cruising!

Any advice on what this could be/
I'm in South Africa and struggling to find a solution to this!

Nic
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  #45 (permalink)  
Old 01-27-2010, 01:34 AM
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Nic. I think your problem with coughing etc while cruising might be adressed to one or more of these:
- Carbs not synchronized
- To lean (spec if exhaust popping) - to small idle jets or not far out enough
- To lean on some of the cylinders due to plugged idle cuircuit. Can be cleaned out.
I've had alot of troubles as you describe, reason was the third above options. Easy to check by using your fingers on the headers. But be quick, or else you'll burn'em.

But first of all you might check your cam to see if all cylinders open equal amount (weared lobes or solid cam need adjustment).
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