Flow testing carburetors... * DATA ADDED *

Although I have taken some pics, I haven't downloaded them from the digi-cam, yet. In the mean time, here's some data from what I've tested:

Carb ------------------------------------------------------------ (TM) --Dry Flow -- Calc'd Wet

Holley 3310-2 with choke ----------------------------------- (A) ----- 796.6 ----- 732.9
Holley 3310-2 with choke ----------------------------------- (B) ----- 811.6 ----- 746.7

Quick Fuel “950” 1.45 v body on Demon RS baseplate -(C) ----- 964.4 ----- 887.2
Quick Fuel “950” 1.45 v body on Demon RS baseplate -(D) ----- 963.0 ----- 886.0

BG (Gold Claw / Demon RS) 1.425 venturi sleeve ------ (C) ----- 960.4 ----- 883.6
BG (Gold Claw / Demon RS) 1.425 venturi sleeve ------ (D) ----- 958.1 ----- 881.5

BG (Gold Claw / Demon RS) 1.500 venturi sleeve ------ (C) ----- 982.9 ----- 904.3
BG (Gold Claw / Demon RS) 1.500 venturi sleeve ------ (D) ---- 1001.3 ----- 921.2

BG (Gold Claw / Demon RS) 1.562 venturi sleeve ------ (C) ----- 994.1 ----- 914.6
BG (Gold Claw / Demon RS) 1.562 venturi sleeve ------ (D) ---- 1012.0 ----- 931.0


Test Methods (TM):
1. Method “A” means this test was of a single primary bore AND then a single secondary bore with the results being added together and the sum multiplied x 2 for a Total Dry Flow #
2. Method “B” means this test was of both primary bores AND then both secondary bores with the results being added together for a Total Dry Flow #
3. Method “C” means this test was of a single bore (either primary OR secondary since the venturi have symmetrical entries) and multiplied the result x 4 for a Total Dry Flow #
4. Method “D” means this test was of either both primary OR both secondary bores (all venturi have symmetrical entries) and multiplied the result x 2 for a Total Dry Flow #

Other comments:
A. Not sure about the discrepancy between why the “A” and “B” results for the Holley 3310-2 varied as much as they did. The primary bore(s) results were virtually identical with both methods; all the variation was experienced during the tests of the secondary bores. I've read where some carbs when testing multiple venturi at the same time show better results than trying to combine the results of the individual venturi... this seems to be an example of that.

B. Test Methods “B” and “D” required lowering the test pressure significantly due to the small capacity of my SF-110. However, trying to test the two highest-flowing combinations using Method “D” required dropping the test pressure so low that I believe that lower pressure introduced a level of inaccuracy not experienced with the other tests.

C. The Calc'd Wet Flow results are simply the Total Dry Flow #s x .92 to subtract some flow for a theoretical 12.5:1 A/F ratio. I have no idea how close this comes to the reality of actually wet-flowing a carb, but it's something of an industry standard. I also suspect that – if it's an "in the ballpark" correction value – that .92 adjustment probably doesn't work for something like an annular booster which has different atomization characteristics that “use” more of the available airflow.

D. The Total Dry Flow #s posted include a 2% temperature correction (reduction) factor on my flow bench for intake results. If you want the “raw” Dry Flow #s, take my Total Dry Flow # and divide by .98 to get the pre-correction #. Example: 982.9 + .98 = 1003.0

E. The Demon RS 1.75” baseplate used for testing the Quick Fuel main body and the various BG (Gold Claw / Demon RS) venturi combinations has slabbed throttle shafts which are supposed to be worth 20 +/- cfm over standard “round” throttle shafts used by most Holley carbs, Proform carbs, Mighty Demon, etc. Quick Fuel uses a similar slabbed throttle shaft with their Q-Series and Race Q carbs.

F. I have no idea how BG came up w/ the wet flow #s they published when the Gold / Silver Claws came out (see the #s I listed in an earlier post on this thread). I know my test equipment is freakin' primitive, and maybe not having a "big gun" flow bench is skewing the peak #s lower for the larger venturi combinations, but...

Great post.

As I read it,
Method A & C blocked off 3 of 4 venturii
Method B & D blocked off 2 of 4 venturii

What were the typical test pressure drops?

When would it be important to flow a carburetor? I don't mean to sound ignorant. I'm just trying to understand the purpose.

Here I am think there was some dark hidden secret.
Like matching 2 carbs for a 2 x 4 tunnel ram.

I was looking all over the web for this info, it was right here the whole time.
Thanks BradH for doing this test!

Same here.

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

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:


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.

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?

Just caught this thread.
Ever considered flow a couple of TQ’s?

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

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.

It would be interesting to know what the actual flow is of the different aftermarket main bodies available. That would be some great data.........

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.

The Super Flow carb testing fixture is pretty similar to what Brad used, only it comes with a 4 hole spacer.
The spacer has a small hole in the center of it to locate it on the pin in the plate.
Then you just rotate it around to test all 4 holes.

The hole in the plate is 1.750, but the holes in the supplied spacer are only 1.687, which is fine if you're testing carbs that don't have a 1.750 throttle bore.

I found a spacer with 1.750 bores to use on the big carbs, and drilled the hole to locate it on the pin.

I also made one to use with 4500 series carbs.

found this on the www http://www.ryanbrownracing.com/Bill_Jones_Page_4.html

I just threw one on my bench and it said 820cfm

Ray, could you pull 20.4" with flowing all barrels?

IDK. Im sorry but I have no idea.

I just threw my 1050 dominator that had the boosters changed to skirted boosters for e85 and it says it flows 1000.

Well, i just tried a 600cfm performer and it says 670cfm.

My method is probably not accurate but I would think comparable for me checking different carbs

You don't know what the test pressure is?

Edit:
Okay, I looked at the site where you got your electronics from.
The picture of the display box isn't all that clear.

Is one of the options for the display 20.4"?
If not, are you using one of the other depressions and converting the numbers to 20.4"?

Thanks. What model number & primary size?

Thanks as well sixpac ! same question as rob.

Guys, I really dont think the way Im doing this is accurate. Im just throwing it on the bench with it converting at 28".

The TQ I have is 9379s. Pri 1.370

Edit: fast68 is schooling me on flowing carbs. My numbers are not accurate and he is making me depressed. lol