DIY_EFI Digest V4 #591

[Greg Hermann]

>
>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