No subsitute?
Paul,
I have done 2 pre-buys on IO-360 A1B6 (angle valve) equipped RV4's one with a Hartzell, the other with a Catto 3 blade. I test flew them both extensively for the customers and reported the following:
Aircraft A (Hartzell) had a 28 lb concorde aircraft battery installed in the baggage compartment lightweight starter/alt, vacuum system, full IFR. It flew very nose-heavy solo with 1/2 fuel.
The perfect RV4 CG occurs with a 50lb tail-wheel weight in level flight attitude. This one had 28 lbs. At full aft trim and 60 knots it required 5-8 lbs of aft stick pressure to hold level flight. It cruised at 200 MPH indicated at 24 squared 11GPH.
Aircraft B (Catto) weighed almost 100 lbs less due to an Odessey PC625 battery (center console), no interior, minimum panel and one coat of light grey paint. It used one of Air Tec's Lexus starters (same as mine) and a B&C mini alt on the accessory case. Level flight Tailwheel weight was 48 lbs. It's performance was stellar, nearly equal to my 290HP HR2 on takeoff. Cruise was at normal RV4 VNE 210 MPH. However, the flying qualities were much better balanced and was much smoother in-flight.
The A1B6 is a tight squeeze under the cowl but if it was engineered well, no worries. All things considered, it's a strong engine, counterbalanced crankshaft, heavy duty everything (Mooney ordered it originally for the 201) and lots in service. The big single mag isn't a problem if you install a flywheel pickup electronic ignition, then you have 1/2 mag for redundancy if the other half breaks away from home. If you can buy it right, go for it. Check the lower Rudder for cracks, elevator as well. Make sure the lower engine mount longerons aren't cracked, something I see alot on big engine RV's. There are many ways to lighten it up, email me offline if I can help.
Questions?
Smokey
[email protected]
PS:
My personal favorite airplane was the A model F16, lighter weight nose.The C has much more thrust, cool avionics and digital flight controls and a better Combat machine for today's environment. For me however it boils down to which one flies better when you "sling it around under G". That applies here too.