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Difference between IDA & IDF Webber Carbs?

General engine tech -- Drag Racing to Circle Track

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Caprimaniac
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Re: Difference between IDA & IDF Webber Carbs?

Post by Caprimaniac »

Remembet - he’s NOT putting these on an IR manifold, but a hi- ram manifold with a plenum....
How to turn GURU in an instant.....
frnkeore
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Re: Difference between IDA & IDF Webber Carbs?

Post by frnkeore »

Ok, let me add a little more info and ask some more questions.

First the reason I bought this Holley 300-275 manifold, was to mount four 4412's on it as I had 3 on hand and bought another about 2 weeks ago. My assumption was that this manifold, would flow, a little better than the Weiand tunnel ram. i.e. the carbs can be set, directly over the straight runners and within 2" of the runners.

This 306, will turn at least 8K, with a 260/266 @ .050 cam and .69 lift with 280 cfm heads. I also have a Super Vic and 850 cfm to try on it first, for a base line and then swap manifolds on the dyno.

Flow numbers are thrown around for Webers. The 45 DCOE's that I used on my DOHC Cosworth, were said to flow about 600 cfm with the largest chokes but, no one offered the Hg for that. Does anyone have any real cfm numbers and Hg ratings? I'm going to assume the 48 IDA would be at least 625 with the largest chokes. 48 IDF, who knows?

The idle circuit is adjustable and the off idle, on the Webers are totally adjustable (E-tube, air corrector and main jets). What am I missing on them not being adjustable to a plenum?

The Holleys, that no one seem to have a reversion to would be a metric 43mm throttle with 35mm chokes, similar to a 44 IDF with 35mm chokes. The 4412 Holley, should flow 1414 cfm @ 1.5 Hg, for 4 carbs. I wouldn't think that a 44 IDF would flow much more than 1500 cfm for 4 of those? But, I asked this because I have a opportunity to get four 48 IDF's at a very good price.

David V, I hope you post the results of you aux venturi work. Are you trying to make them work the same as the IDA?
chimpvalet
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Re: Difference between IDA & IDF Webber Carbs?

Post by chimpvalet »

as I recall, a Dave Bean catalogue listed flow of 485 CFM with 45DCOE using 38 mm venturi when measured at 1.5 inches Hg pressure drop,, as was the standard method for rating 4 bbls.
frnkeore
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Re: Difference between IDA & IDF Webber Carbs?

Post by frnkeore »

chimpvalet, thank you for that.

That would be 685 @ 3Hg if tested under the 2v std.

It's to bad that they came up with 2 different standards for carb testing.
Geoff2
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Re: Difference between IDA & IDF Webber Carbs?

Post by Geoff2 »

In one of DVs books, he shows a chart for 40 & 45 DCOE carb with various choke sizes measured at 1.5"Hg. 45 DCOE with 38mm chokes 218 cfm [ one barrel ].
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Re: Difference between IDA & IDF Webber Carbs?

Post by chimpvalet »

Review of the Bean catalog confirms I recalled correctly, 485CFM for 45DCOE w/ 38mm chokes. This info was, in fact, attributed in the catalog to David Vizard's work. Don't know how to square the discrepancy with figures above.
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