Which FAB, RV-6A, SDS O-360 vertical draft with O-320 lower cowl

Not sure which FAB to purchase. Any insight appreciated.

I'm building an RV-6A and have an O-320 lower cowl.

Engine will be vertical draft O-360 except you could call it an IO since it will have SDS EFI.

I gather:
* The O-360 lower cowl has a taller scoop to accept the taller O-360 carburetor versus O-320.
* The O-360 lower cowl has a larger IML(1) versus O-320 and the O-360 FAB has a larger OML(1) to match.
* So only an O-320 FAB will fit into my O-320 lower cowl.
* I know about the add-on O-360 lower scoop but why go that way if I don't have to?

Since the SDS IO-360 throttle body is shorter than an O-320 carburetor even with an aluminum flange attached to mate to the FAB, I'm thinking I can use my O-320 lower cowl with an O-360 engine. Something I don't know is whether the elevation of the carburetor surface on the sump is different O-360 versus O-320.

Here are some photos of an O-320 carburetor, SDS IO-360 throttle body, and 2-/12" dia aluminum flange. Not shown is the silicone hose coupler that will attach the throttle body to the flange; this hose can be adjusted in length to make the overall height from sump face to FAB face whatever it needs to be.

And to add to my confusion, Vans offers six different FABs, three -320 and three -360.

FAB-320-1 O-320 Carbureted
FAB-360/540 O-360/540 Vertical Draft with Carburetor or Fuel Injection; also IO-320 with Bendix Fuel Injection
FAB-320 ELLISON-1 O-320 with Ellison Throttle Body
FAB-360/540 ELLISON O-360/540 with Ellison Throttle Body
FAB-320 AP-1 O-320 with Airflow Performance System
FAB-360/540 AP O-360/540 with Airflow Performance System







1) Outer Mold Line, an aeroshell's outer surface, mainly used in the context of aviation. Inner Mold Line, an aeroshell's inner surface, mainly used in the context of aviation.

SDS Throttle Body Vertical Induction to FAB Photos

I am installing SDS EFI system on RV10. Anybody have pictures of how they transitioned from SDS throttle body on vertical induction engine to Vans FAB?

Interface SDSEFI TB to Vans FAB

To interface SDSEFI throttle body to Vans FAB simply use an aluminum flange at the FAB, a silicone hose coupling, and a new FAB top plate you make yourself.

2-1/2" hose is shown for the O-360 on page 15 of the SDS installation manual (the hose is sitting on the flange pipe rather than the pipe being inserted so don't be fooled by that): http://www.sdsefi.com/em5aeromanrev14.pdf

For O-540 the hose will be 3-1/2" ID as stated by SDS for 80 mm TB: http://www.sdsefi.com/lycoming.htm

Hose such as Vibrant 2716B (blue, they also have 2716 black and 2716R red) is 3-1/2" ID: https://www.summitracing.com/parts/vpe-2716b/overview/

ACS has aluminum flanges but only up to 3". Hopefully SDS has a solution.

Here's a photo of my O-360 TB: