1963 - 289 Rocker Covers

[Dan Case]

Originally Posted by CompClassics

SAI utilized both 48 IDM and 48 IDA Weber systems on the engines they built. Both systems were very tunable for small block Ford applications and can be used on bib block applications as well. 48s have als been used successfully on four cylinder VW and Porsche engines as well. I know of several stock to mildly built Ford small block engines that run 48 IDA Weber systems. Yes, the 48 Webers might be challenging to properly tune but the performance gain once dialed in is awesome!

Part of tunable means several sizes of factory and aftermarket "chokes" (slip in main venturi) can be swapped in and out. The flow "size" can be changed dramatically to suit driver tastes, altitudes, fuel mixes, engine size, and degree of other modifications from inlet air temperature to size and lengths of exhaust components. Of course there is an near limitless set of combinations of fuel jets, air bleeds, air horn heights (two different ones Cobra wise 1964-65), different inlet valve sizes, different auxiliary venturi sizes, and different auxiliary venturi designs (A style for Porsches was claimed to help signal strength as camshaft designs got more aggressive.) to go along with "tuning" for different engines and conditions.

[Gaz64]

Originally Posted by Dan Case

Part of tunable means several sizes of factory and aftermarket "chokes" (slip in main venturi) can be swapped in and out. The flow "size" can be changed dramatically to suit driver tastes, altitudes, engine size, and degree of other modifications from inlet air temperature to size and lengths of exhaust components. Of course there is an near limitless set of combinations of fuel jets and air bleeds to go along with "tuning" for different engines and conditions.

Yes, that's correct.

Factory choke size is 37mm.

48s are fine on mild 289s to near wild BBs.

You can 45 chokes for 48s, which is just like a sleeve.