carb flowing what depression

[msj442]

ok i have always been into carbs mainly holleys and was wondering what the industry uses for depression? i always modified carbs and then tuned on the motor but never really flowed them to see what i gained. i have heard that its 3". so do i flow it at 3" and look at comparison flow for 28" then thats the figure? shed some light on this it would be greatly appreciated.

max


well did some searching and it seems that the standard is 20" , right?

[Flash]

[2seater]

To expand a little more: typical Holley 2-barrels are rated @ 3" Hg and 4-barrel @ 1.5" Hg. You need to convert to inches of H2O as Flash mentioned to get a direct comparison to the carb. flow rating.

[Tony]

Yup,
Traditionally two barrel carbies are flowed (and rated) at three inches of mercury, because that is fairly typical of the depressions measured at flat out full power on the "low performance" workhorse engines two barrels are normally fitted to.

Four barrels are measured (and rated) at 1.5 inches of mercury. That is fairly typical of what you might measure on typical higher performance factory engines these carbs are usually found on.

And therefore logically, a 300 CFM rated two barrel carb will be a lot smaller than a 300 CFM rated four barrel carb.

[49-1183904562]

[color=#000000]Max;

Thomas is the Carb Guy, from a prior post but allready stated above

[quote]While I agree with the vast part of your reply Rick, I have to make a correction/modification to your post:

"During the carburetor wars Holly and Carter both had advertised CFM these carbs were flowed at 40

[msj442]

thanks guys.

max

[thomasvaught-1]

Yep, I worked at one time for the Holley Engineering (Research/WHO) in Warren, Michigan many years ago.

You might recognize a name in this information.



Good Holley Tri-Power website.

Tom Vaught