World's smallest supercharged four-stroke V8 engine now in production


October 2, 2012

The Conley Stinger 609 supercharged four-cycle V8 gasoline engine - 6.09 cubic inches and 9.5 horsepower at 10,000 rpm (Photo: Conley Precision Engines)

The Conley Stinger 609 supercharged four-cycle V8 gasoline engine - 6.09 cubic inches and 9.5 horsepower at 10,000 rpm (Photo: Conley Precision Engines)

Image Gallery (19 images)

Giant-scale model cars (and airplanes) powered by small gasoline engines have been popular with adult racers for quite a few years now. The largest scale models available through conventional RC hobby outlets are one-fifth or one-sixth scale, but the serious racers go quarter-scale. Now the smallest (quarter-scale) blown V8 gasoline engine in commercial production is being turned out by Conley Precision Engines to power.

A quarter-scale gasoline-powered car is about 1.2 m (4 feet) in length, weighs around 50 kg (110 lbs), and can top out at over 160 kph (100 mph). The engines for such large models are usually two-cycle engines not dissimilar from the engines that power weedwackers and leaf blowers, typically beginning at about 33 cc (2.0 cu. in.) displacement, providing 3 to 4 hp at 6-8000 rpm.

Even the larger engines for quarter scale models are simple and relatively inexpensive. For example, a 160 cc (10 cu. in.) displacement gasoline motor that provides 17 hp at 9000 rpm while weighing only 4 kg (8.8 lbs) is available for about US$1000. (I did say relatively inexpensive). This is plenty of power for any quarter-scale wheeled vehicle one might want to race.

Gary Conley holding a production model of his new supercharged V8 engine (Photo: Conley Precision Engines)

Why then is the racing community reacting with crackling excitement over the Conley Stinger 609, a new quarter-scale V8 with supercharging, 100 cc (6.09 cu. in.) displacement, and a power output of 9.5 horsepower at 10,000 rpm – especially with a list price over US$7000? Simply enough, other engines don't look or sound right.

If you are going to spend a significant portion of a year's salary on a scale model car, expecting to own a true scale model isn't unreasonable. For example, the 1969 Dodge Charger Daytona, one of the quintessential Detroit muscle cars, was 5.75 m (18.9 ft.) long, weighed about 1690 kg (3730 lbs), and had a 7.0 l (426 cu in) hemi V8 that put out 425 hp. Scaling to one-quarter the size would give a model 1.44 m (4.7 ft) in length and weighing about 26 kg (57 lb). The scaled engine would have a displacement of 109 cc (6.6 cu in) with an output of 6.6 horsepower.

To some extent, the changes required to make a scale model look and perform in a properly scaled manner can be accomplished by changing the materials of which the model is constructed. For example, using strict scaling the loading on the tires on the pavement is considerably smaller for the scale model than for the original car. This makes for poorer handling and performance, as the power of the engine will cause the tires to break free, wasting power and losing traction in curves. It may be possible to save the performance and the appearance of the model, for example, by substituting a rubber for the tires that either has proportionally larger contact areas (a more compliant material) or a stickier rubber, or both. Such substitutions may allow a scale model to perform properly while keeping its scale appearance.

Quarter-scale model of a 1923 roadster equipped with the Conley Stinger 609 V8 (Photo: Conley Precision Engines)

But a powered scale model of a car isn't just one with the right appearance, or even if properly scale performance is produced. A great deal of the enjoyment of racing is the sound of the car, and especially of the engine. Nothing else in the world quite sounds like a big block V8 turning over, then running up through the power curve. The rumble at low speeds is hypnotic, while the special screaming wail at high rpms adds greatly to the excitement of the race. In short, serious quarter-scale racers want their models to sound right, and this largely drives the demand for the Conley 609. It sounds like the real thing – only two octaves higher in pitch.

Internal parts of the Conley Stinger 609 V8 engine (Photo: Conley Precision Engines)

Of course, a scale-model engine also encounters difficulties associated with simple scaling. A particular problem comes from lubrication – it is very hard to adequately lubricate the cylinder and piston walls to survive running at 10,000 rpm. This problem was eventually solved with the help of manufacturing engineers from Sunnen Products Co., a leader in precision honing who worked with Conley to make the engine's cylinder liners. It proved necessary to deeply hone a cross-hatched pattern in the cylinder liners, and then to plateau hone the liners to remove any lips and edges protruding from the first set of patterns. The cylinder liners then had sufficient excess oil capacity to adjust to the movements of the piston, and were smooth enough to significantly reduce the effects of those movements by maintaining closer tolerances between the pistons and the cylinder liners. The production models can be run for long periods at high rpm without excessive heating or wear.

The Conley Stinger 609 V-8 has an electric starter and a centrifugal clutch as standard equipment, and is available with or without the supercharger. The list price of the Stinger 609 in its naturally aspirated form is US$5695, although lower prices are available from some suppliers. The supercharger allows the engine to produce about 60 percent more power for an additional cost of US$1700.

Rear end of quarter-scale drag racecar equipped with the Conley Stinger 609 V8 (Photo: Conley Precision Engines)

Giant-scale model car racing is a high-tech sport which can be approached without having to put a new mortgage on the house. It also doesn't require "hold harmless" clauses in life insurance policies against accidents during races. The practitioners are an enthusiastic, outgoing lot who truly enjoy their hobby. More power to them.

Source: Conley Precision Engines via Design News

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer. All articles by Brian Dodson

A video of this would be real nice.


Might have to switch Kymera back to Gas now...

Jason Woods

Since it is supercharged they should look at selling them to UAV manufacturer's. They would have to add variable timing for changing altitudes though....

Brian: Small, amazing - yes but ICE - NO and not in production and available. Big difference.


To all: Feast your eyes (and ears) on the videos here:


Small is beautiful, but what are the emissions/kW?


The most amazing facts about this engine are that it is in limited production and that Mr. Conley appears to have done the difficult engineering of creating a practical power plant. Congratulations, Mr. Conley. I am highly impressed.

Marvin McConoughey

100 cc and still not 10 hp? production motorcycles are already past this onceuponatime barrier. And unsupercharged. Somebody better go back and look at something? 100 cc should come out near 15 horse! no, really! or is it merely that a 8 cyl is massively frictional.

why not use small scale and some "3-d printing" machines? then we could do some r and d ..things like rotary sleive valving for better breathing per volume and be rid of poppet valves which were introduced in the late middle ages in mining water draining pumps and still are the default.

I also notice injectors atop and below the "supercharger" depending the pix? any difference noticable?

Walt Stawicki

It seems clear that Conley was not trying to develop an engine for pratical future use. He was developing a scale model engine for a particular purpose. On that concept he has succeeded in a grand manner!



Cutest toy I have ever seen. Now do a Rolls Royce Merlin!!


Brian MCC, that V-12 is an air motor, not an internal combustion engine.

There is a super tiny Ferrari V-12 that is an ICE, with a complete scale model Ferrari wrapped around it.

Gregg Eshelman

Why not use it in a full-scale car? When I visited France in 1963 I test-drove a 2-hp Citroen. Not exactly a sports car but it provided basic transportation at low cost. This is 9.5 hp, enough to move such a lightweight car. What kind of mileage does it get?

Jon Roland

Although not a production model I have seen some years ago a fully functional 1/4 scale model of Ferrari in one of the CNC related magazines. It was a garage project of a production engineer.


I can just imagine running a pair of these in a small 'hot' hatch designed for 4WD. The existing computer wizardry should be able to 'split' the power between ends and the sound would be amazing! Actually, being that small, it should be possible to squeeze into a skooter or moped (V8 Vespa, anyone?) for enjoyable and incredulous looks from passers-by! Or - how about a tiny hybrid electric Citycar?

The Skud

I think you are on to something The Skud. Perhaps one can have a small hybrid where the tiny v8 could power a generator and not be attached to the drive system. One could still brag about having a V8 in ones small car and it would be true.

I think it would make any RC vehicle faster; boats, planes, cars, etc. :)


Gregg mentions driving a Citroen with only 2 horsepower. Apparently he doesn't realize that the designation "2 CV" - cheval vapeur if I remember my French from a years-ago class, which translates to "2 steam horses," was not an actual dynamometer-measure of the output power, but some sort of legal calculation for taxation or licensing purposes. I'm sure a bit of web-searching could find the actual power, and probably also the way the CV rating was determined. It was probably in the range of the early VW Beetles of the same era, which was 25 hp in the earliest models imported, and 40 in 1963 (I have owned both).


Re 2 CV,

Apparently my memory of French spelling wasn't very good - the actual word for horse is chevaux. Searching 2 CV in Wikipedia will get a lengthy article, including horsepower ratings in 1963 of 15 or 18 - probably because of its lightweight construction. Unfortunately I didn't find weights in the Wikipedia article. A 1953 Beetle with me in it (about 150 lb. at the time) weighed almost exactly a ton (2000 lb.). Its engine produced 25 hp, and a 1963 one - 40 hp (my latest Beetle, now with a somewhat larger engine).


Gregg Eshelman, I love that little V12, but it's actuated with compressed air and does not produce work :(

William Wayne
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