 How big of an engine are Weber 44IDFs good for? |
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| Tdskip |
 Aug 17 2020, 07:52 PM
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#1
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Advanced Member  Group: Members Posts: 3,736 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None 
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I have a pair of good Weber 44 IDF carbs but thinking they may be too small for the 2.7l Type4 being rebuilt. Anyone have some coaching on carb sizing?
Edit - maybe up to a 2256? Thanks! |
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| yeahmag |
Aug 18 2020, 12:02 AM
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#2
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Advanced Member Group: Members Posts: 2,448 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California
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See the following for a formula on cylinder volume vs. rpm vs. venturi.
http://www.performanceoriented.com/throttl...-venturi-sizing My guess is you would want a 40mm venturi, so a 48mm IDF or DRLA. |
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| Mark Henry |
Aug 18 2020, 06:00 AM
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#3
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Run the 44's, I'd use 36mm vents for a car that sees the street.
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| Tdskip |
Aug 18 2020, 08:18 AM
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#4
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Advanced Member Group: Members Posts: 3,736 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None
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Thank you for the responses.
Guidance on this seems to be all over the map, but I think I’m more concerned about giving it too much carb rather than not enough. I’d rather have good off idle behavior and what worries me about the 48s is they may ultimately produce more power but it’s at a RPM that all rarely be at in a streetcar. I assume that’s behind your suggestion Mark Henry? Great resource @yeahmag |
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| Mark Henry |
Aug 18 2020, 10:21 AM
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#5
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
The Performance Oriented site info is for a six and IDA Webers.
I'd spend my coin on better heads, etc. before I worried about the 44's. |
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| yeahmag |
Aug 18 2020, 10:22 AM
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#6
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Advanced Member Group: Members Posts: 2,448 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California
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The single cylinder chart still works. It's similar, if not the same as what is in the CB Superformance book for Dellortos and I've used the model many times. Granted, I'm not really after low end for my cars, but I drive them around town easily.
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| VaccaRabite |
Aug 18 2020, 12:47 PM
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#7
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En Garde! Group: Admin Posts: 13,728 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region
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I ran dual 44s on a 2056 and they were necked down as far as I could get them and they were still too big. All my power was from 4k-6K rpm. For a 2270 44s would be about perfect.
That said - Get fuel injection. Zach |
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| Tdskip |
Aug 18 2020, 12:53 PM
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#8
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Advanced Member Group: Members Posts: 3,736 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None
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Thanks for all of the ongoing discussion, very helpful.
@VaccaRabite - I have a barely used set of Weber 44 IDF carbs that came with the race car, so I would love to put fuel injection on this but I think I’m gonna try running these first. FI would be a great upgrade at some point however! |
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| JmuRiz |
Aug 19 2020, 08:07 AM
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#9
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914 Guru Group: Members Posts: 5,567 Joined: 30-December 02 From: NoVA Member No.: 50 Region Association: MidAtlantic Region
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QUOTE(VaccaRabite @ Aug 18 2020, 10:47 AM)  I ran dual 44s on a 2056 and they were necked down as far as I could get them and they were still too big. All my power was from 4k-6K rpm. For a 2270 44s would be about perfect. That said - Get fuel injection. Zach (IMG:style_emoticons/default/agree.gif) ...if you can afford it. In a perfect world I'd have EFI and electric a/c on the 914 and 356 |
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| Mark Henry |
Aug 19 2020, 09:49 AM
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#10
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
I built a 2.7 engine for a speedster replica back in the mid 2000's and I used 44's. I know I posted some pics but I did a search and I can't find it. Very fast little car, but the bug gearing was too short.
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| stownsen914 |
Aug 20 2020, 08:55 AM
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#11
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Senior Member Group: Members Posts: 946 Joined: 3-October 06 From: Ossining, NY Member No.: 6,985 Region Association: None |
QUOTE(VaccaRabite @ Aug 18 2020, 02:47 PM) I ran dual 44s on a 2056 and they were necked down as far as I could get them and they were still too big. All my power was from 4k-6K rpm. Similar experience here. I ran 44's on a modified 2.0L with headers. The carbs were too big and powerband was similar to what is mentioned above. |
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| Tdskip |
Aug 20 2020, 09:47 AM
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#12
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Advanced Member Group: Members Posts: 3,736 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None
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Thanks for all of the responses and shared experiences.
Brought the 44's to the shop and explained my drivability goals and they agreed with the coaching you all have provided. It has been very helpful to get all of this feedback from you - thank you again. |
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