DIY_EFI Digest V4 #591

[Doug Dayson]

> Date: Wed, 20 Oct 1999 07:44:46 -0600
> From: bearbvd at cmn.net (Greg Hermann)
> Subject: Re: DIY_EFI Digest V4 #591
> 
> >
> >Currently my engine only consumes somewhere around 625 cfm max...I believe
> >that the BB TBI's flow 670 cfm so I too have thought about a BB TBI...Holley
> >makes a SB TBI manifold good for 6000 rpm as well...I'll have to check it's
> >height though?
> >
> Hi Doug--
> 
> Watch out for the flow on things like Holley Pro-Jection. 2 barrel carbs
> are rated for flow (in cfm) at 3 inches of Hg pressure drop. 4 barrel carbs
> are rated for flow at 1.5 in. Hg pressure drop--NOBODY seems to publish the
> pressure drop at which things like pro-jection are flow rated---BUT--I have
> talked to folks who have tried the pro-jection, and found, by
> experience--their engine does _ NOT _ flow nearly as well as with a 4
> barrel of similar flow rating--that Holley must be rating the projection
> units at some (unknown) higher pressure drop!!!
> 
>  (Just for general info, the multiplier for comparing 2 barrel carbs to 4
> barrels is .707. A 350 cfm rated 2 barrel only flows 247.5 cfm if rated
> using the same test conditions which are used for rating a 4 barrel!)
> 
> Regards, Greg

Thanks Greg...I had completely forgotten that fact...quite right you are!

I'll try Holley's Tech Support and report back...

Doug