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[M30B35] Triple weber 45 DCOE installation

jmackro

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so if I understand the carbs in 40 with 34 chokes for my engine to have the maximum torque
and maybe 36 chokes to get the horses higher rpm
I don't think it's quite that simple, but I'm no authority.

the m30b35 making its maximum power at 5700 rpm
OK, well the numbers I ran in post #17 used a lower RPM figure, so perhaps 36's would be better if you plan to regularly run at 5,700 RPM. But for normal street use, I suspect you'd get a better idle, and plenty of torque & HP with 34's. For a race engine, with a cam that won't let it idle anyways, larger chokes might be preferable.
 
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Ohmess

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Hi guys
thank you for the informations
so if I understand the carbs in 40 with 34 chokes for my engine to have the maximum torque
and maybe 36 chokes to get the horses higher rpm
the m30b35 making its maximum power at 5700 rpm
i will try to install an afr gauge for the set of the jetting
but i will start with the formula for it
Be careful a out going too big.

With larger verturis you are not reducing max torque, but are instead moving the torque curve upward relative to rpm. At any given rpm under 2500 rpm, the engine will not pull as hard, which will make the car feel slower. The engine will not pull as hard from a standing start, you will want to run it up higher in the rev range before shifting into second, and you will be downshifting sooner at higher rpm.

And you probably will need to get above 4500 rpm before you feel your hp gains. Most street cars don't spend a lot of time running above 4500 rpm.
 

Stevehose

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Remember that changing chokes will affect the rest of your jetting which means time, frustration, cursing, and more $$$. Get a set of jet drill bits from Pierce Manifold, download the Weber Tuning Manual and read it, and start with smallest recommended jet and air bleed sizes. Then you can drill out until you like your AFR. I’d say start with 34 and commit your jetting to that, like mentioned above, you won’t spend a lot of time at the redline so jet for torque it is much more sensitive to jetting that the high rpm horsepower number. You’ll notice the lack of acceleration from too big a choke before a few extra hp.
 

jc971

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Ok i understand

after what i read on dave home page
what I could note for my engine: 3.5 220cv 5700rpm
caburator: 40
venturi: 34
main jet: 136/138
air corrector: 190
emulsion tube: F2
idle jet: 45f9 or 55f8
 

jc971

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and what do you think about this configuration :
carburetor :40
venturi : 35
main jet : 140
air corrector : 190
emulsion tube : F2
idle jet : 45/55 F8 or F9

I know I would not have much opportunity to use my engine in high rpm but I'm afraid it lacks power at high rpm
I think the B35 already has power at low rpm
 

jmackro

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and what do you think about this configuration :
I think you should try it and see how it feels. Use an oxygen sensor to measure how it delivers fuel under a variety of conditions. Make adjustments accordingly.

It's pretty tough to just look at a list of specifications and advise you how it will perform - Weber jetting depends on your altitude, the octane of gas you use, your engine's cams, compression ratio, model of 40 DCOE that you're using, phase of the moon, your height & weight, etc. etc. etc.
 

Stevehose

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The 35 will affect your torque and progression more than it will noticeably affect your horsepower. If you want a place to start, start small and drill up:

carburetor :40
venturi : 34
main jet : 130
air corrector : 180
emulsion tube : not sure yet, where did you get F2?
idle jet : 50 F9 (F9 is richer than F8 so can be drilled leaner)

I suspect this will be overall a little lean but can always go richer on fuel bores and leaner on air bleeds with a drill. In order to take advantage of larger chokes you'll really need a hotter cam and some headers.
 

jc971

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I have a camshaft of code 3 which means that it is a 272 degree in my stock
I hesitate to make the change in my b35 cylinder head this will allow me to mount my original ignition system without modifications, and maybe a power gain ?

I quote a conversation I found on this forum

Identifying Stamp

I believe the camshafts all have the same part number, but the grind is identified by a number stamped on the back end or the camshaft. This is edited from a previous discussion:

Remove the Cover on the backside of the head and look at the number that is stamped on the cam.

1 = 260° (2500) lift 6.8471mm (8.9mm at valve)

2 = 264° (early 2800) lift 7.4228mm (9.7mm at valve)

3 = 272° (late 2800 and all 3.0) lift 7.4228mm (9.7mm at valve)

For comparison, the milder Schrick grind has 282º duration and lift of 8.4/10.9mm. There are differences in the lift figures quoted on the various websites, but these are based on a 1.3 rocker arm ratio.
 

rsporsche

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i don't think changing the cam will do anything to the ignition system unless you get the cam for an old school distributor ... which would change things. i would think that a schrick would make the webers come alive
 
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