Question about Jay Browns Intake Comparo. Book

[FERoadster]

Jay: From a discussion on the FEForum.  Your test of the Edelbrock F380 3X2 intake stated that at WOT there was still 2.2" of vacuum.

Is there a way to back into the amount of CFM that actually went through the carbs?  I got rid of all of my 94's and 81's and have standardized on Stromberg WW's since they are considerably larger,a newer (better?) design and have parts readily available.

I'm wondering CFM differences from the Ford-Holley 94's and the Strombergs. I have read that the WW's flow over 250 CFM where 94's flow someplace around 150 CFM. Your test is the only one I've seen that maxes out flow.

Richard >>> FERoadster

[Heo]

I have one of those intakes and you could order
them for 2bbl Rochester so there is material
att the base to drill them for Rochester
and open upp the runners to match
if that make any difference i dont know
but im going to try that when and if i have
any spare time
Stromberg WW wich carb is that?
The early y-Block got a 3 bolt carb thats
look like the 94 but is much bigger ...well
over one inch throtlle blades ..1 inch and
some /16 dont remember now
Think 56 is the biggest one

[jayb]

Jay: From a discussion on the FEForum.  Your test of the Edelbrock F380 3X2 intake stated that at WOT there was still 2.2" of vacuum.

Is there a way to back into the amount of CFM that actually went through the carbs? 
Richard >>> FERoadster

Normally yes, because the dyno measures the cfm taken by the engine.  However, in the case of that test I don't know if I had the dyno's inlet air turbines connected; it would have been difficult to fit them over the 3 small carb openings without leaks, so I would have had to make a box with three holes for the carbs, tape that in place, and then cut one or two larger holes for the air turbines to flow air into the box.  I probably still have the dyno data from that test; I will look it up and try to post what I find later - Jay

[FERoadster]

Jay: Thanks for the reply.  My ides was that if you had some data on what the 428 pulled (CFM) at a certain RPM and the vacuum there you could relate it and make a SWAG about how much flowed thru the 94's. If vacuum on a certain carb-intake combo was say 1" and the 94's were say 3.5  it would be possible to calculate flow.

It's been 43 years since my fluid flow class in University but I did work for the natural Gas industry so I was exposed to the calculations. I'll have to check some of my books from the GasCo.

Heo: yes  my Edelbrock 3X2 has the Stromberg WW's  and was the 4 bolt base version of the F380. The larger Holley-Ford carbs were the 81 and I think the 48. 97 was the smallest then 94,81 and 48.

Thanks  Richard

[jayb]

OK, I found the data for the 390 Stroker dyno mule and it looks like I did take the time to make up an airbox so I could get the airflow data on the F380 intake.  Here are two charts; the first chart shows the manifold vacuum over the course of the dyno pull, and the second chart shows the airflow.  Sorry about the graphs, they are a little difficult to read:





Just for a point of comparison, here is a graph of the airflow from the Blue Thunder 2X4 intake, which basically showed zero manifold vacuum:



Hope that helps, Richard.  If you come up with some kind of a calculation on this for the carbs, please post it here for interest - Jay

[FERoadster]

Jay and others: Did some searching  on HAMB  for a short time today and looked for CFM data on 94's
Here is my preliminary finding. First off. 2bbl carbs are rated at 3" vacuum where 4bbl carbs are at 1.5" so I'm including some # for each.
The Holley-Ford carbs are designated by the venturi size in decimals of an inch. ie 94=.94, 81, 48 and Stromberg 97 as well .97

So flow ratings are as follows

Carb Model    CFM@3.0"  CFM@1.5"

94                   251            176
81                   192            135
48                   250            175
LZ                   229            160
ECG                264             185

Strom 97         214             150
Strom WW       357             250   not sure of which venturi size 2 variations one @ 1.125 and another @ 1.1875

So in the Graph above 585 CFM out of the trio of 94's exceeded the 1.5" calculation and the chart shows 2.2" vacuum or nearing the 2bbl manufacturers design data #3".

Good for me to know. Jay thanks for the info and publishing the book. A picture of my WW's
 

[Heo]

The ouestion is how much the intake is capable to flow
it got pretty small runners

[machoneman]

Neat. Never saw the two different flow ratings for two barrel carbs side by side before, even knowing though 3.0 was used for them. I'm a tad amazed at just how little cfm even 3 carbs flow, other than the WW series. 'Course, when three deuces were highly popular long ago engines of that era did not have great overall flow from poor heads, tortured exhausts, small camshafts and rpms were a lot lower too. Thanks for the posts!   

[Mike Caruso]

Neat. Never saw the two different flow ratings for two barrel carbs side by side before, even knowing though 3.0 was used for them. I'm a tad amazed at just how little cfm even 3 carbs flow, other than the WW series. 'Course, when three deuces were highly popular long ago engines of that era did not have great overall flow from poor heads, tortured exhausts, small camshafts and rpms were a lot lower too. Thanks for the posts!

Bob now that you have seen it once side by side you will never forget there is a big difference in numbers at different test pressure's.
Mike

[FERoadster]

My take on this whole scenario is that whatever the engineering test/design pressure was you can go into chaotic flow parameters and F#@CK up all calculations.
Jay's stroker pulled more than the manifold or carb's were designed and just went thru pure dynamics.  Kind of "damn the torpedo's"
Now I'd like to post other 2bbl flows especially the Ford 3X2 carbs and the venerable Holley 500cfm 2bbl.

Richard