Hello Buick V8 forumites: My ride is a bit different than most on your site however I thought it would be interesting to join you as there appears to be a wealth of expertise on board and I look forward to tapping it on occasion with engine-related queries. Under the cowling of my camouflaged mistress (a 70% scale replica 1940 Mk1 Spitfire fighter) resides an all-aluminum Buick 215 V8, from a convertible 1962 Skylark. The scale of the aircraft was determined from the width between exhaust flange faces of the 215, exactly 70% that of the legendary Rolls-Royce Merlin II from Battle of Britain fame. The 215 (sitting backwards in the mounts) has been modified a fair bit for operation in a scaled warbird including: a 231 V6 timing cover and high volume oil pump with remote filter and Stewart-Warner in-wing oil cooler, a hand-built high volume coolant pump plumbed to the under-wing custom 4-row radiator (fitted with saddle-type expansion tank), TR-8 heads, Egge high compression (11.5:1) pistons, forged rods, Erson high-torque cam, Offenhauser(John Wolff Racing) ultra-low-profile dual-plane intake manifold mounting an Edelbrock 1404 de-choked and ported carb. She sports authentic Rolls-Royce fish-tail exhausts that give her a reasonable semblance of that unmistakable Merlin V-12 symphony. Propeller speed reduction is 1.67:1 achieved through a purpose-built Autoflight (NZ) gearbox bolted to the 215's original crankshaft/light-weight flywheel through an elastomeric coupling. The engine is currently being re-assembled after a failure of the original oil pump and further modifications. Prior to the engine rebuild, level flight cruise at 3600 engine RPM was an honest 160 mph with a 1200 fpm rate-of-climb. With anticipated post-modification power gains, I am hoping for a cruise of 170+ mph and 1500 fpm rate-of climb. As an interesting closing side note: the Skylark's original hydraulic convertible top pump still manages to power the Spit's characteristic outward retracting landing gear. Best regards, 1940Spitguy
No idea yet. Your question is certainly valid Jim as most aircraft engines cruise in the 2200-2400 rpm range with 1500-2000 hr TBO's. This bird was built to fly mainly on rare and special occasions (Battle of Britain Day(Sept 15th), Remembrance Day(Nov 11th) and the occasional airshow and fly-in. Even if she were to show signs of needing overhaul in 300-400 hrs, that would be plenty of TBO.
I assume that you are using a manual prop rpm control. How many RPMs for the engine during the take off run? Same elliptical wing design as that used by Mitchell?
Prop is only ground adjustable at this point as original cog-belt PSRU would not support constant speed. Prior to mods, I saw 4300 rpm on takeoff and 3500-3600 in cruise at 1.62:1 reduction. I upped the ratio a bit anticipating a bit more power and torque. If she runs a bit too fast in cruise at current pitch setting, I will coarsen the prop another degree or two. Ultimately I will get Whirlwind or Craig Catto in Oregon to build me a constant speed prop when I know what the real numbers are. The wing is pretty much an exact copy of Mitchell's incredible elliptical airfoil. It flies like a dream.
