I have an EXP-390 installed in my RV-8. I originally had a superior XP 400 but when they bought back my engine I ordered the Lycoming 390. One of the main things to be aware of is if you use the FM-200 you will need to either use the RV 14 version of the engine and exhaust with the intake adapter that angles the FM-200 fuel injector body enough for the mixture arm to clear the lower cowling. I had to install a small blister on the bottom side of my cowl to clear the mixture arm when using the superior cold air induction. I also CNC machined a new mixture arm and cut 1/2” off the mixture shaft.
When I sent back the XP 400 I kept the superior cold air induction and installed that on the Lycoming 390. I also have the veteranmen trombone exhaust system. The adapter plate Lycoming uses to angle the fuel injector will not work on anything except for the new Lycoming RV 14 set up.
So basically I have the same layout as the new Lycoming 390 for the RV 14 but my FM-200 is fixed directly to the cold air sump without the angled adapter plate.
Van’s has a video on installing the 390 in the RV 14 which shows the angled adapter plate and mixture/throttle cable mount that you will need.
You will also need to make your own snorkel or modify a Van’s snorkel since the FM-200 is larger diameter and mounts differently than the van’s snorkel.
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Here’s the EAA RV-14 IO-390-EXP video that explains the above, details start at at the 26 mins point