Valach Motors VM-170 B2-4T
Completely encapsulated valve train 
CNC milled crankcase 
Sensational smooth running and high torque 
Spontaneous throttle response and smooth midrange transition 
Extremely low vibration throughout the RPM range because of the four stroke principle 
Honda valves and valve seats 
Walbro carburetor 
Valach microprocessor controlled ignition with auto advance and retard 
An ignition integrated voltage converter allows the use of two LiPo cells 
VM-engines are now being produced with state of the art machines and methods

The Valach engines VM 170B2-4T Mk.2 looks just like an original aero engine, only smaller, it runs smoothly like an original aero engine and above all it sounds like an original aero engine. 
Due to being a four stroke, the low vibration is nothing but sensational, and torque is really high. The response to the throttle being opened is so smooth without the slightest attempt to surge, making the Valach VM 170B2-4T Mk.2 absolutely ideal for your big aerobatic model.

Being a four stroke with a large capacity produces a very realistic full-size aircraft sound. With a relatively small silencer the sound level is very low rather like a small saloon car.

The Valach VM 170B2-4T Mk.2 is a four stroke OHV engine running on petrol/oil mixture. Valves and their seats are manufactured by Honda, ensuring a very high quality. The totally encapsulated valve train reduces sound, as well as ensuring the rocker arms are well lubricated. Due to the steel cylinder liners this engine will have a long life.

The recommended RPM range for the VM 170B2-4T Mk.2 on the ground is 4,500?5,000.
 
We have measured the following RPM rates on a well run in VM 170B2-4T:

Fiala 2 blade propellers:
32x14" ca. 5050 RPM
34x12" ca. 5000 RPM  good static thrust/sound
34x14" ca. 4700 RPM  higher speed
36x14" ca. 4050 RPM  this is too big

Fiala 3 blade propellers:
30x14" ca. 4850 RPM

Super Silence CF-2-blade:
32x19" ca. 4700 RPM
 
On the VM 170B2-4T installed in the Pitts Special S1-S we use the Fiala 34x12" prop as this has proven to be ideal. Immediately after landing, that means with a hot engine, 28.5 kp static thrust was measured. When  winds are strong  I change over to a 34x14" Fiala. As would be expected the ground speed is increased, unfortunately the Pitts sound is partly lost thereby.
The Fiala propellers are very efficient, this being due to minimal blade thickness. They sound especially good on four stroke engines.
 
Specifications:
Displacement:  170 cc
Output:  ca. 13 hp
Bore:  52 mm
Stroke:  40 mm
Width:  352 mm
Length from engine mount to prop hub:  185 mm
Weight: complete with ignition, two exhaust stacks, prop washer and prop bolts  5545 g
Ignition voltage range:  4.8 - 9 V
Idle RPM:  900 rpm
Max RPM:  6200 rpm
Fiala Prop 2-Blade: 32x14", 34x12", 34x14", 36x14"
 
Fiala Prop 3-Blade: 30x14"