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#1363882 - 01/12/13 11:05 AM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
MPerry Offline


Registered: 01/20/03
Posts: 11657
Loc: Fitchburg,Massachusetts
Is it common for carbs to be off much from their advertised cfm?

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#1363883 - 01/12/13 11:08 AM Re: Flow testing carburetors... * DATA ADDED * [Re: MPerry]
tboomer Offline



Registered: 01/20/03
Posts: 21753
Loc: The frozen wasteland of Iowa
Neat testing,Brad! You are thinking outside of the bun again! But come on....Put the damn thing together already!!
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#1363884 - 01/14/13 09:23 AM Re: Flow testing carburetors... * DATA ADDED * [Re: tboomer]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13461
Loc: Valhalla... eventually
I did this for myself, not for Moparts, but am still a bit surprised by the lack of any related comments.

Is the lack of response to this post (despite over 1000 hits) due to the what seems to be a continuing trend on this forum that "tech is boring", or because all of about four people on this board thought this data was even worth discussing?

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#1363885 - 01/14/13 09:25 AM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
tboomer Offline



Registered: 01/20/03
Posts: 21753
Loc: The frozen wasteland of Iowa
I did find it interesting!
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#1363886 - 01/14/13 09:26 AM Re: Flow testing carburetors... * DATA ADDED * [Re: tboomer]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13461
Loc: Valhalla... eventually
Quote:

...Put the damn thing together already!!



Yep, back to working on the engine. The next steps that come to mind are...
- degree the cam and...
- find out what the length of the new pushrods need to be, then...
- assemble the heads.


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#1363887 - 01/14/13 09:40 AM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
MPerry Offline


Registered: 01/20/03
Posts: 11657
Loc: Fitchburg,Massachusetts
Well its easy to be interested. That is why so many views. Its harder to understand what is being done. Myself included. When I see flow data it is usually cylinder heads.

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#1363888 - 01/14/13 02:40 PM Re: Flow testing carburetors... * DATA ADDED * [Re: MPerry]
tex013 Offline
pro stock

Registered: 03/27/09
Posts: 1576
Loc: Sydney,Australia
Brad,
thanks for the post/info.i guess it does show that you can only compare carbs based on their specifications,venturi/throttle size,not what the manufacturer calls them

Tex
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stepped it up a bit more
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#1363889 - 01/14/13 06:38 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
BSB67 Online   content
master

Registered: 02/19/05
Posts: 3411
Loc: Prospect, PA
I too find it interesting, and appreciate the info, but don't know what to make of it either.

I've wondered about the 1.56/1.60 venturi 4150 carbs, and the flow restriction contribution from the throttle shaft and throttle plate. Ideally, the only restriction would the venturi and booster. So, I would find it interesting to see the same tests without the shafts/plates. Not sure what the value of that would be either.
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#1363890 - 01/14/13 08:55 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BSB67]
Triple Threat Offline


Registered: 01/19/03
Posts: 6170
Loc: Renton Washington
Quote:

I too find it interesting, and appreciate the info, but don't know what to make of it either.
/quote]

I think that about sums it up for the average reader. I look forward to an on track comparison as well!


Edited by Triple Threat (01/14/13 08:55 PM)
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#1363891 - 01/14/13 09:46 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
forphorty Offline
pro stock

Registered: 11/26/06
Posts: 1277
Loc: oklahoma
Quote:

I did this for myself, not for Moparts, but am still a bit surprised by the lack of any related comments.

Is the lack of response to this post (despite over 1000 hits) due to the what seems to be a continuing trend on this forum that "tech is boring", or because all of about four people on this board thought this data was even worth discussing?


I appreciate the info. Pretty interesting stuff . I would be interested in seeing how various modifications affect cfm. Example: a stock street type carb flowed OOTB, then with the choke tower chopped off,then thinned shafts and button head butterfly screws, etc.

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#2428513 - 01/03/18 06:50 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
65Fury440 Offline
enthusiast

Registered: 03/09/13
Posts: 388
Loc: Spring Hill Fl
I was looking all over the web for this info, it was right here the whole time.
Thanks BradH for doing this test!

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#2428671 - 01/03/18 10:57 PM Re: Flow testing carburetors... * DATA ADDED * [Re: 65Fury440]
Sport440 Offline
master

Registered: 01/20/03
Posts: 6428
Loc: Canton, Ohio
Same here.

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#2428723 - 01/04/18 01:03 AM Re: Flow testing carburetors... * DATA ADDED * [Re: Sport440]
sixpackgut Offline
Drag Week Mod Champion

Registered: 06/08/03
Posts: 9031
Loc: Charleston
When I made my flow bench I used a 4150 pattern to mount my bore adapter to. So I have just flowed carbs all 4 bbls all at once.

One day Im on the phone with Eddie Miller, he is telling me he is putting 2 90mm throttle bodies on his tunnel ram. Says they flow 1100 cfm each. Im like BS, no way. Hold on, I have a 90 here. Throw it on my bench. 1086. Wow. Ok

On the phone with Thumper, i ask him what a particular carb I have is supposed to flow, he said he thinks 1200. I throw it on the bench and it reads 1168 or something. Ok

You just tested a bunch on the dyno which seems to be a much better indicator of what might work best unless to much data has you scratching your head from that test session
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#2428838 - 01/04/18 10:00 AM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10540
Loc: So. Burlington, Vt.
When I flow a carb, I test all barrels individually, then add the numbers together.

4bbl carbs are rated at 1.5"hg test pressure, which is like 20.4"h2o.
I could probably pull 20.4" of pressure flowing 2bbls at a time for most 4150 carbs, but I'd have to make a different fixture to do it that way.

I very rarely flow test carbs anymore.
Pick the size you feel you need....... Then most of the power is in the metering.

To that point:
Quote:
You just tested a bunch on the dyno which seems to be a much better indicator of what might work best unless to much data has you scratching your head from that test session


Of the carbs we ran on Brads motor, only one had the metering off far enough where we couldn't make pulls without fear of doing some damage.
Of the other carbs tested, the one with the smallest venturi(and least flow) made as much power as any of the others.
It was doing a better job of mixing the fuel.
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#2429688 - 01/05/18 08:39 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
astjp2 Offline
master

Registered: 01/18/11
Posts: 4106
Loc: Utah and Alaska
I wish someone would build a billet carb base that has a built in shear plate bottoms...maybe you could test a shear plate vs a regular carb bottom?
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#2429700 - 01/05/18 09:01 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
Rob C Offline
super stock

Registered: 03/04/05
Posts: 709
Loc: Earth
Just caught this thread.
Ever considered flow a couple of TQ’s?

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#2429867 - 01/06/18 09:40 AM Re: Flow testing carburetors... * DATA ADDED * [Re: Rob C]
moparx Offline
master

Registered: 09/03/03
Posts: 8119
Loc: north of coder
Originally Posted By Rob C

Ever considered flow a couple of TQ’s?

i really like those carbs, and that would be of interest to me as well.
beer

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#2429947 - 01/06/18 11:35 AM Re: Flow testing carburetors... * DATA ADDED * [Re: moparx]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13461
Loc: Valhalla... eventually
Originally Posted By moparx
Originally Posted By Rob C

Ever considered flow a couple of TQ’s?

i really like those carbs, and that would be of interest to me as well.
beer

Sorry folks, but this is really old data... 5 years. I won't be doing any carb flow bench testing in the foreseeable future, nor do I have a spreadbore test fixture for a TQ.

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#2430009 - 01/06/18 12:47 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
ccdave Online   content
The Ultimate

Registered: 01/22/03
Posts: 1705
Loc: Mopar Country, Mi
It would be interesting to know what the actual flow is of the different aftermarket main bodies available. That would be some great data.........

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#2430030 - 01/06/18 01:26 PM Re: Flow testing carburetors... * DATA ADDED * [Re: BradH]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10540
Loc: So. Burlington, Vt.
If you want what I would consider even close to "accurate" flow data from carbs, they really should be flowed with all barrels at the same time, at full capacity(1.5"hg).
And that means you need a big honkin flow bench.

And even better yet....... Wet flow tested.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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