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Weber 40ies and the 2.4

2297 Views 3 Replies 3 Participants Last post by  Travis
Weber 40ies and the 2.4

The source of my less than stellar top end is beginning to come to light…

For any of you who make or buy a 2.4 here the weber 40ies are NOT the car best for the engine (as Bob clearly advised and warned about) as they are too small. For those of you who didn’t listen (sheepish grin, thinner pocketbook now and no comment) or just happened to have a set of 40ies and were sure you could make them work.... here is the patch, just understand you are losing a lot of HP with the dinky carbs. If you race get 48ies, for street 45ies

But the 40ies are great for low end up to 70mph or so (which is fine for solo) but will fall off after 4500-5000 rpms. That is my current problem.

I have already added bigger fuel line and an electric fuel pump.

Here is what can be done if you have 40ies and need to run them for some reason till you save enough to get the proper carbs. My source fore this is Mike Pierce of Pierce manifold a weber distributer in Ca. He has owned and raced Opel’s before (1900 rally kadets) and has a soft spot for them. He also advises 40ies are not the the carbs for a 2.4

Please note Dual DCOE’s are fine for a 1900 on the street.

What I have right now in the DCOE 40ies

F16 emulsion tubes
165-195 and all in between main jets --------------
180 air to 210 ----------------------
45 idle ------------------------ Idles fine with these
36 choke ------------------------ this is a big as they get
50 exhaust jet ------------------
175.w needle ------------------THIS IS WAY TO SMALLL!!!!

I am getting going to 300 needles and it has been suggested that I remove the chokes entirely. I am awaiting the parts and will first try it with the bigger needles, which should gain me some top end and then again with the chokes removed which should get me more.

I eventually will be going to the DCOE 45/48 and selling my 40ies with a VAST assortment (including the correct jetting for a stock 1900 which is not is listed above) for Webers jets, tube, correctors etc. when I become once again gainfully employed

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Calvin, you could also consider retarding your cam timing a little bit to improve mid/top end power. This is assuming you have sufficient exhaust valve-to-piston clearance.

Or at a later date, a bigger camshaft altogether maybe?

For a big engine like a 2.4 they seem to 'like' a wider lobe separation angle (112 degrees) than a typical 1.9/2.0 Opel engine (they do well with 108 degrees). You will also find that a 2.4 can handle a lot of duration, 245-250 degrees duration @.050" is not that radical for a big 2.4, and you'll need this much cam to make power to 7000 rpms or so.

Hey thanks for that tip. I will think about that. Right now I will rescue what I have as the Carbs work like an unplanned rev limiter and Pierce Manifold seemed to think that I would see a big improvement with the needle change. I will post result.

what do you think about their idea of yanking the main chokes? They said it was an old rally trick. Can it hurt something?

Do you think that adding/changing the air horns might improve things at all? Is there a formula to follow with those?

Thank you,

I wouldn't expect the small carbs to act 'like a rev limiter'. Once you've maxed out the flow of the carb your torque should start dropping but I'd expect your HP to remain constant as the revs increase until the point that the motor is processing less air than the carbs can flow.

Thoughts Bob?

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