40 IDF-how much hp?

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40 IDF-how much hp?

Post by skipnsb » Fri Sep 05, 2014 2:47 pm

I have a 3 pair of 40 IDF Webbers. I see people have used these on anything from stock 1600 to a 2.7 T4.

I understand the venturis are changeable.

What horsepower will these reasonably support in a occasional street car?

I recently acquired a 912, 914, Thing, a rail, and a Manx, all need engines.

I am hoping to build a strong T4 for the Porsches with the 2.0 heads.

I have a big valve head T1 motor, 1776 I think, older heads make unknown, and some stock 1600 dp.

So I hope to build 2 stout T4 and 3 various T1.

The T4 will be 2056 with stockish 2.0 heads, a better cam don't know which. How bad will the 40's hurt this combination? Should I go bigger?

Does the 40 work well as a single carb on a 1776?

Thank you.

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Dale M.
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Re: 40 IDF-how much hp?

Post by Dale M. » Mon Sep 08, 2014 8:19 am

The 40's will probably be good up to 100-125hp.... For any engine over about 1950cc I would recommends going to 44's though if you want max performance, but if you want good performance and economy the 40's will probably make you happy no matter what size engine you build... Its a great step up over "stock" carbs........

Have two engine both over 2000cc and they produce "about" 110hp at the wheels (figuring about 130-135 hp at crankshaft with about 20% loss through gear train) on the dyno runs, one engine has Weber 44 idf's and one has HPMX 44's....

Was never in favor of single center mount carb.... It requires manifold heat which most manifolds do not provide.... And it will not unleash total capabilities of engine...

Like any setup, its all about jetting and venturi size ... Getting the perfect match requires some work on your part...

Lives his life vicariously through his own self.
1970 "Kellison Sand Piper Roadster"

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