wrote:=20 Ed, Lynn, Bill or anyone. I'm trying to figure out how to extrapolate various air flow figures = which have different vacuum testing parameters such as those with 10" of = water verses those with 12" of water and 20.4" of water. I don't know = where the 20.4" of water comes from, but apparently it does exist. I assume there is some calculation which can be applied? I'm only concerned with extrapolating from one ( known value like = 10") to another ( like 12") - for comparison purposes. George ( down under) -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.484 / Virus Database: 269.12.4/969 - Release Date: = 23/08/2007 4:04 PM ------=_NextPart_000_009E_01C7E7C9.30D22670 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Tracy

Thanks for that info.

I have been trying to get my mind around how to establish the best = vacuum=20 signal around idle, and like you said it's a pretty small signal.

The flat ground needles seem to have = overcome this=20 with their design as they claim that the flat side ( rear) of the needle = creates=20 a vacuum sufficient to lift fuel 6" to 8" with 1 PSI fuel pressure = - which=20 I found difficult to comprehend. These carbs have the so called 'perfect = inlet=20 shape', I assume by this they mean no venturi ( choke) or butterfly=20 restrictions.

What also amazes me is that in all the = Internet=20 carb calculators provide answers in CFM, yet these carb manufacturers = rarely=20 give that type of flow information, especially Edelbrock and Aero Carb - = I=20 wonder why?

Revmaster didn't have it readily to = hand but did go=20 to the trouble to find out. It all seems very strange to = me!!

Further investigation = required!!

George ( down under)

I think this is the spec on ventury vacuum (V V) at max specified = CFM. Performance carbs (generally 4 barrels) are designed with = about 1/2=20 the ventury drop as "grocery getter" carb designs. The less the = V V, the=20 better WOT performance (more MAP) but the harder it is to = design due to=20 the smaller signal. 10" H2O is a pretty small signal for MAX = CFM.

BTW, This is unrelated to throat size.

Tracy Crook

On 8/23/07, George=20 Lendich <lendich@optusnet.com.au>=20 wrote:=20

Ed, Lynn, Bill or = anyone.

I'm trying to figure out how to = extrapolate=20 various air flow figures which have different vacuum testing = parameters such=20 as those with 10" of water verses those with 12" of water and 20.4" = of=20 water. I don't know where the 20.4" of water comes from, but = apparently it=20 does exist.

I assume there is some calculation = which can be=20 applied?

I'm only concerned with = extrapolating from one=20 ( known value like 10") to another ( like 12") - for comparison = purposes.

George ( down=20 under)

No virus found in this incoming message.
Checked by AVG Free = Edition.
Version: 7.5.484 / Virus Database: 269.12.4/969 - Release = Date:=20 23/08/2007 4:04 PM
------=_NextPart_000_009E_01C7E7C9.30D22670--