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Weber Tuning
A question for all you Weber Gurus out there:
I have just completed building a 2.7L engine built to the following specs:
1. 9.5:1 C/R
2. 911 S cams
3. Standard 2.7L valve sizes but heads & manifolds ported & careflly matched.
4. Case mods for air flow as per Bruce Anderson.
5. 1-5/8" exhaust headers into Super Trap 'mufflers'
6. Standard single plug ignition
7. Weber 40 IDA 3C caburetors with 34mm chokes
In other words, nothing radical...
On a chassis dyno, the engine makes good power (about 180hp at the wheels at 6000rpm) but has an annoying hole in the power curve from 3000rpm to about 4200rpm where the power curve is completely flat. At 3000rpm, the fuel/air ratio falls vertically from about 14:1 to less than 11:1 (i.e. VERY rich) until at 4200 (i.e. the exact range of the flat spot) it starts to lean out until at 6000rpm it is over 14.5:1 (i.e. way too lean) at which point we shut the engine down! Because we didn't have a box of compatible jets to hand, we had to call it quits and think about the problem.
Sooo... my question is - does anyone have a similar setup and if so, can you tell me what emulsion tubes, main jets and air correctors you run? We currently have F3 emulsion tubes, 170 main jets (and I can't remember what the air correctors are).
Our gut feel is we need smaller main jets and smaller air correctors but are unsure of the effect of the various emulsion tubes available.
I would be very greatful of any input from those of you who may have direct experience of this before we start changing things...
Kindest regards,
Mark Lamberton
Sydney
Australia
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