Weber Info - Cfm

[A20A1]

Well I decided to spend a few hours seeing what performance, well actually CFM gains the 32/36 and 38 weber carbs really have to offer. All I need now is the Stock CFM of the Keihin.

This is just a list of what I found. I don't think there was a positive CFM for either carb, as each site had their own different CFM rating for each carb... I made my own average at the bottom of the list.

- 255 CFM 32/36
- 300 CFM 32/36
- 325 CFM 32/36
- 330 CFM 32/36

- 350 CFM 38
- 360 CFM 38
- 370 CFM 38
- 380 CFM 38
- 390 CFM 38
- 400 CFM 38

- APROXIMATELY 325 CFM 32/36 AVERAGE
- APROXIMATELY 375 CFM 38/38 AVERAGE

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I've found a few more sites that said the 32/36 was 325 CFM
I'm still looking for more 38 ratings since they seem to be all over the place.

[shepherd79]

hmmm very interesting.
so 325-350 cfm Holley should do just fine.

[A20A1]

If I find anymore 360+ CFM's for the 38, I'll start to get worried about getting it.

[shepherd79]

how many did you find so far?
why would you worry about it? dual sidedrafters pull more than 360cfm and it seems to be just fine.

[grocerygetter]

Originally posted by shepherd79

so 325-350 cfm Holley should do just fine.

i like the sound of this


now if i could just come up with an adapter to bolt a 390 holley 4bbl.:super:

[A20A1]

Originally posted by shepherd79
how many did you find so far?

Everytime I find a different CFM I add it to the list above.

Then I just adjust the average.

[shepherd79]

Originally posted by grocerygetter
i like the sound of this


now if i could just come up with an adapter to bolt a 390 holley 4bbl.:super:

well, i am woking on 2bbl Holley right now, Mike is working on 4bbl carb. i am planning to finish my project at the end of the summer.

[grocerygetter]

well, i am woking on 2bbl Holley right now, Mike is working on 4bbl carb. i am planning to finish my project at the end of the summer.

wow, i new for sure i was going to get blasted for that remark.
you used to be able to buy manifolds to bolt 390 holleys to 2000cc fords. so hey, why not. figure you'll just have to jet that baby down a bit.

[A20A1]

350 is more then enough unless you plan to split the carb down the center.... then you could use a 390 - 400 cfm carb and split the carb into 2.... so you'd have 2 barrels feed only 2 cylinders.

and maybe some type of vaccum connection between the 2 halvs of the manifold to equalise vacuum...

[A20A1]

I found a site listing more on rating CFM and all that other jazz. But I lost it.
There was good info on carbs and how important the CFM rating really is.

[lostforawhile]

i like the sound of this


now if i could just come up with an adapter to bolt a 390 holley 4bbl.:super:

why not get an aluminum holley spacer and weld it into an extra manifold? just do a cut out and weld off the coolant passage going to the carb. i was looking at an extra one and thinking about doing that.

[A20A1]

Yup thats how you do it.

[A20A1]

wow, i new for sure i was going to get blasted for that remark.
you used to be able to buy manifolds to bolt 390 holleys to 2000cc fords. so hey, why not. figure you'll just have to jet that baby down a bit.

I was looking for manifolds from the Pontiac Super Duty 4 Cylinder Motor I think it was 2.5 L ?

[FyreDaug]

Not to jack the thread, but if you were to run 4 carbs instead of 2 (1 cylinder for 1 carb) what would be the cfm you would use?

[A20A1]

I dunno, 40mm - 45mm webers seem to be good on our cars. If you can find the CFM for one of their barrels then I guess that is the number, but DCOE's you can change the chokes... so I dunno

- 400 cfm Weber 45 DCOE
- 530 cfm Weber 45 DCOE


As long as it flows 60 CFM @ 6,800 RPM @ 100% VE ( Volumetric Efficiency )
That doesn't seem right, does it?

1995 cc displacement
211 to 250 cfm Single Plane Manifold @ 6,800 RPM
230 - 288 cfm Divided Plane Manifold @ 6,800 RPM


2366 cc
257 to 304 cfm Single Plane Manifold @ 6,800 RPM
281 to 351 cfm Divided Plane Manifold @ 6,800 RPM


I did more searching

http://www.mergetel.com/~fraso/RasoE.../Carb-Flow.htm

here is a nice article.


http://www.triumphspitfire.com/carbchoices.html

Can I assume you want to use motorcycle carbs?
"The Mikuni and Keihin high performance motorcycle carburetors. So you ask. Motorcycle carburetors on a car? Why not? A carburetor is a carburetor, and does not care what it is mounted too, nor will it react differently. These motorcycle racing carburetors flow a tremendous amount of cfm over their best competitors (Weber DCOE) matched size"
http://www.triumphspitfire.com/images/carbs/figA.jpg

http://www.prirace.com/

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[A20A1]

22R
Stock Asian 326 cfm
Weber 32/36 325 cfm
Weber 38/38 390 cfm

[Cant Stop]

how about the dual carbs off the 86-87 preludes anyone ever get that done yet? i still havent gotten it started yet.
still trying to find someone to rejet them.

[RamThis]

Yup thats how you do it.

Holey Schnikeys, someone's droppin a 4 holer on a little Honda??? Wont this lose all the low end torque the car ever had? I knew that bigger carbs were better in most instances, but, there is a give and take with carb sizes right? Smaller carb will give great velocity and be peppy around town driving, and large carbs will make the car feel like a dog around town, but when you hit WOT on the hiway, it will wind out faster. Or am I wrong on this?

[A20A1]

I guess you missed the thread about the manifold.
https://www.3geez.com/showthread.php?t=37554

[RamThis]

I guess you missed the thread about the manifold.
https://www.3geez.com/showthread.php?t=37554

Man you guys sure get serious with the mods on these Hondas!!! I dont think Im ever going to really mod this car, at least, no where near this extent, as I dont plan to keep it very long.

But, you guys sure are creative with your carb and intake systems. How much power are you guys creating with these little 2.0's? Im curious as to how well these highly modded cars run on the street. Are you guys racing them, or just trying to make them perform like a more modern EFI engine that puts out alot more power than the 3G stock motor? Either way, kudos, guys, looks like some good work to me!

[A20A1]

Nice info on ignition timing, idle adjustment and air filter sizing per application.
http://www.mgbmga.com/tech/mgb19.htm