Holey Cowl
Mark/Bill,
As mentioned above, Van's has made several different cowl iterations for the
Ah-Vee-Four over the years.
Initially, the old vinyl-ester cowls most of us original builders dealt with came in two varieties, Fixed Pitch and Constant Speed. The carb air inlet scoops were identical (small) as the FAB, cold air induction, cell phones and VAF for that matter hadn't yet been invented. It was up to us builders to fabricate an air box to effect efficient air induction. The
Redneck Ram Air Box I cobbled together in 1994 with primary ram air/alternate K&N filtered air is still working well on my RV4 to this day.
When Van introduced the FAB in the late 1990's, many of us early builders were suspect of the claimed 1" MP loss through a filter versus our Ram air setups. However comma, having now seen the FAB "in action" over the past 20 years I'm a convert, it really works. Later, Vans would introduce the new Pre-Preg fiberglass cowls now standard on all their kits. The RV4 Pre Preg cowls come in 2 varieties as well for the 0-320 and 0-360. This due to the size difference of the FAB for the different induction systems.
As Axel mentioned, Van's sells the bigger scoop for those with older cowls installing an 0-360 or those upgrading from the lower displacement as Chris so eloquently elaborated. You could easily modify an existing cowl for a snorkel arrangement, buy why? It's a 40+ year old design well proven over time. To quote Einstein,
"why argue with success?" As far as recommended exhaust configurations, from personal experience helping numerous RV4 builders over the years, I would select the Vetterman 4-pipe arrangement for exhaust.
If you desire an Angle valve IO-360 up front, plan to do some "fitting" to shoehorn it into your FWF.
My Dos Centavos...
V/R
Smokey