how would i figure out cfm rates on 94's or 97's?

i'm looking for some info on the cfm ratings on 94's and 97's. formulas, personal experiance, etc! so.... what do ya know about it?

 

you put your thumb in your mouth and blow hard

 

2 bbl carbs are rated at 3" of vacuum,
while 4 bbl carbs are rated at 1 1/2",
so comparisons can be difficult.

In theory,you could compare the venturi area to a known carb.

 

is someone cranky 'couse they have to work all day tomorrow??!!

 

From Vintage Speed's website. Regarding the Stromberg 48 and 97. Sorry i can't help with the 94.

"The 48 makes a great hot rod carb because of
increased cfm (approx. 170) over the 155 cfm of the "97".

Hope that helps.
Anally extracted, i would think the 94 would be close to the 97.

 

The bigger-is-better thing might work in some cases, but on our flathead powered dragster, the 97s (four of them) outran the same setup with 48s.

For what it's worth, the cfm ratings of any of these carbs that I have heard are all in the 140-180 range. Not sure at what vacuum.

 

Try Rumbleseat's stuff: http://www.flatheadv8.org/rumblest/intro.htm

select "fuel". Stromberg's are on page 9, the C-H/Holley/Ford carbs on page 14.

Mike

 

Traditionally the 97's were rated at about 175 cfm... HOWEVER, I recently read that when they are flowed at the same vacuum as modern carbs are tested, they test at about 225 cfm. It would make sense, when comparing flow rates, that we would all use the same vacuum readings otherwise you are comparings apples to oranges. @ 225 CFM you can easily see why most Flatheads are overcarbed with 3 deuces.

 

I never knew that.

Is there an alternative formula to the approximation CID X RPM / 3456 = CFM for carbs rated at 3" of vacuum?

Here's some information from http://www.btc-bci.com/~billben/fuel.htm
# 48’s had a 1.031’ venturi and are rated at 175 cfm. They were stock on ‘34 and ‘35 V-8’s with 221 cu. inches. Main jets were 48 at sea level.
# 81’s had a 0.812” venturi and are rated at 135 cfm. They were stock on ‘37 and ‘38 V-S 60’s.
# 97’s had a 0.969” venturi and are rated at 150 cfm. They were stock on ‘36 and ‘37 V-S’s with 221 cu. inches. Main jets were 45 and power valves were #65 at sea level.
# L’s had a 1.000” venturi and are rated at 160 cfm. They came on ‘36 and ‘37 Lincoln V-12’s.

--Matt

 

Stromberg 48 rated 175 variations 167-182, St 81 135 CFM v 130-142, St97 150 CFM v144-155, St. LZ 160 CFM v 158-162. Holley 92 142 CFM v 140-145, H.94-59 155 CFM v 150-158, H.94- 8BA 162 CFM 158-165, H. ECG 185 CFM v 184-190. Alt carb formula CIDX2X.8=CFM about the same as 5000 max RPM using other formula.

 

right on for the help guys!the reason i'm asking is, i just picked up a '68 440 to use in a modified project i'm getting together. i have a 2x4 intake i want to run with adapter plates to make it a 4x2. the motor came stock with a carter 750. so i want to figure out how close i can come to that. i don't want to get into recaming, etc. i think my power to weight ratio is fine with out doing anything to the motor!!!!