Perfection is Almost Good Enough
The world’s smallest production V-8 engine is smokin’ hot – not smoking – after its builder uses honing from Sunnen to optimize oil-control at quarter-scale. His perseverance over setbacks pays off, as collectors and gear heads around the world “gotta have one.”
Posted: July 8, 2013
“I learned decades worth of information about honing from Sunnen,” he said. “Learning how to line hone an engine block straight and true was quite an achievement. We could not get the tandem cam and crank bores on the same centerline without this. Using a three stone mandrel, I can hold 0.001 in, end to end, on a six inch workpiece.”
He adds, “After the investment cast aluminum block is machined and the main bearing is torqued down, we line hone the bores for the crankshaft and the camshaft. The 4140 camshaft rides on the T6 aluminum, just like a real Viper engine. The crank and cam bores are about 0.875 in and 0.625 in, respectively. We machine the 7075 connecting rods and install a bearing insert that allows the engine to start dry, without oil pressure, and we experience no wear on the crank or con rods. The smallest bores we hone are the tops of the con rods – about 0.248 in, and the piston pin bores. I stack a set of rods on a ground pin using the large end of the rod, then hone the pin bores to ensure they are all at the exact same height and straight.”
Conley stresses he designs for longevity. “Our use of 6-bolt mains makes our lower almost bulletproof,” he said. “We also have crankcase ventilation and split keepers on the valves to keep them in place. Oil filtration is critical on a small engine, too. It’s amazing what comes out of the filter system.”
He sources the parts that he doesn’t create himself, including quarter-scale spark plugs from miniature model engine builder Paul Knapp in Payson, AZ, rings from Dave McMillan at D.A.M. Good Engineering (San Jose, CA) and castings from Invest Cast, Inc. (Minneapolis, MN).
“I’ve been very fortunate to find people who share my passion for creating these engines,” said Conley. “Bill Walker, Sr. at Invest Cast assured me that his group could cast the parts I needed, and they delivered.”
In terms of output, the normally aspirated Stinger produces about 4.5 hp, while the supercharger version hits 9.5 hp at 10,000 rpm. Today, Conley sells the engines with a test stand for collectors, or as crate motors for builders of model boats or other adult toys.
“A customer in Austria recently purchased two supercharged engines for an 8 ft offshore boat,” he said. He also offers the engines in a quarter-scale 1934 Ford or 1923 T-bucket roadster, and has his own 7-foot dragster.
Conley was named the Joe Martin Foundation’s 2012 “Metalworking Craftsman of the Year” and enjoys an air of celebrity as he makes appearances at trade shows, signing autographs and holding court with gear heads. “I’m an overnight success that took 30 years,” he mused. And his backlog grows as people find new ways to put the mini engines to work in quarter-scale vehicles of all types.
Conley Precision Engines, Inc., 825 Duane Street, Glen Ellyn, IL 60137, www.conleyprecision.com.
Sunnen Products Company, 7910 Manchester Road, St. Louis, MO 63143, 800-325-3670, sales@sunnen.com, www.sunnen.com.
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