MOTORES ULTRAVAIR
Introducing the UltraVair 2
cylinder opposed, four stroke ultralight engine.
Stock configuration includes:
The UltraVair engine is made from
a 6 cylinder General Motors Corvair engine cut down to 2 cylinders similar to
the way the VW engine is converted to an ultralight engine. The prototype
produces an estimated 35 hp at 3,500 rpm. It produces this power with stock
pistons, crankshaft and camshaft. The stock Corvair has hydraulic lifters and
strong through-bolts holding the case halves together. It also has the exhaust
ports facing down and a removable top cover and oil pan. No special head or
case boring is needed. This eliminates expense and the removal of material that
weakens engine components
The prototype
has single ignition using a 2 cylinder Fairbanks Morse magneto from a Wisconsin
engine. The carburetor is a side-draft Bendix from a Harley Davidson
motorcycle. The engine only weighs 80 pounds dry and runs very smooth due to
the fact that the stock pistons and rods are very light, reducing reciprocating
weight and the tendency to shuffle. The crankshaft is modified with weld-on
counterweights.
UltraVair cylinder heads are extremely simple to modify and both heads can be
made out of one stock Corvair head. A simple aluminum plate is welded in to
complete the rocker box area and no modification is required for the rocker
arms. The valve covers are cut down from stock covers and bolt on. The stock
Corvair heads are very rugged and well finned. When cut for two cylinder use,
the heads retain fins all the way around.
Stock pistons, cylinders and rods can be used. On the prototype, the best two
cylinders out of the six were honed and re-ringed. The block is completed with
basic machine work. Welding on the block is not required, but can be done to
improve cosmetic appearance. Corvair parts are readily mavailable from several
suppliers and total engine cost is perfect for the homebuilder budget.
Specifications:
Bore |
3.437 inches (87.3 mm) |
Stroke |
2.94 inches (74.7mm) |
Displacement |
54.6 cubic inches (894cc) |
Width |
27.5 inches |
Weight |
80 lbs (includes intake and magneto) |
Horsepower |
35 @ 3,500 rpm (estimated) |
Future changes include, battery ignition, charging system, dual
ignition, fuel pump, and electric starter.