Carb flow

D

dunlop01

Member
Ok I picked up a carb this week and it was tagged 9.1 Is that air flow or what I am no motor builder or carb guy so what do you think the 9.1 is
 
On the old Simmons carb compare bench the manometer read from 0 to 10.0. a good one on mine would be anything over 9.0. A carb used as a standard was compared to the carb you were testing so no two builders would use the same numbers as standard, one builder may test the same carb as another builder and get different results. -- Chuck
 
Chuck is spot on.
FWIW, we have a Simmons carb comparator for sale if anyone is interested.
I picked it up in a buy-out and already have two Superflow benches.
148928912_910170319806174_6764919530815824169_n.jpg


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Ok so : is it a air flow or fuel signal ?
I understand not cfm .
My Initial thought must be wrong . Y'all are too kind :giggle: .
 
dunlop01:

It is an air flow number for the Simmons Carb Comparator. The Simmons simply "compared" one carb to another. A 9.1, if compared to a pretty good carb is actually very good. However, if 9.1 is compared to a stock, never reamed carb (if memory serves me, such a carb would be in the 7.8-8.1 range) it would not be nearly as good. It is simply air through the air horn and bore and is not a measurement of fuel flow. CMac
 
It's not a measurement of airflow as much as it is a comparison of airflow.
Think of a scale from 1-10 with 10 being the best.
If your very best carb flowed 10 - then a 9.1 would be pretty decent.
Now, it would not necessarily be in the top 10%, as other carbs wouldn't fall below about 7 or 7.5 typically if they are all built the same.
It works quite well for it's intended purpose (much like a dyno - to "compare" rather than to match numbers from one machine to another.)

At one time there was a sticky post on this site for building your own homemade flow bench - very similar to this unit.
 
CarlsonMotorsports said:
It's not a measurement of airflow as much as it is a comparison of airflow.
Think of a scale from 1-10 with 10 being the best.
If your very best carb flowed 10 - then a 9.1 would be pretty decent.
Now, it would not necessarily be in the top 10%, as other carbs wouldn't fall below about 7 or 7.5 typically if they are all built the same.
It works quite well for it's intended purpose (much like a dyno - to "compare" rather than to match numbers from one machine to another.)

At one time there was a sticky post on this site for building your own homemade flow bench - very similar to this unit.
Click to expand...
CarlsonMotorsports said:
Chuck is spot on.
FWIW, we have a Simmons carb comparator for sale if anyone is interested.
I picked it up in a buy-out and already have two Superflow benches.
View attachment 14163

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
How much are you trying to get out of this flow bench Brian?
 
CarlsonMotorsports said:
It's not a measurement of airflow as much as it is a comparison of airflow.
Think of a scale from 1-10 with 10 being the best.
If your very best carb flowed 10 - then a 9.1 would be pretty decent.
Now, it would not necessarily be in the top 10%, as other carbs wouldn't fall below about 7 or 7.5 typically if they are all built the same.
It works quite well for it's intended purpose (much like a dyno - to "compare" rather than to match numbers from one machine to another.)

At one time there was a sticky post on this site for building your own homemade flow bench - very similar to this unit.
Click to expand...
That's when I joined the site...though now it says I joined in 2020 :-(
 
I have a Simmons, it is a valuable tool. I need to replace the horizontal manometer. Does anyone have any suggestions on replacing it with something that may make it even better? Anyone try digital?
 
one of the flowbench designs I had in my book was basically a Simmons. used the same Dwyer manometers.. Chip the one you see at the top with red oil in it is a 40-1.. Check out Dwyer web site for other styles that would work. the 40-1 is actually is reading 1" of air flow they just divided it into tenths then hundreds.. first design we used had a pitot tube on the output side of the wet/dry vac we used to pull air.. later design used an orifice and measured the difference in vacuum across it..(differential style of bench)

hopefully lots of folks made their own from the article.
 
Chipg56 said:
I have a Simmons, it is a valuable tool. I need to replace the horizontal manometer. Does anyone have any suggestions on replacing it with something that may make it even better? Anyone try digital?
Click to expand...
Chip, I have 2 or 3 new manometers like used on the Simmons. -- Chuck
 
A guy told me to run a .750" reamer through my Carbs. I haven't but, what's y'alls thoughts on this being done by the Backyard Mechanic?
 
Oh, and should I keep the Swirly things that are in there? Probably wouldn't fit after Reaming, now that I think about it.
 
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