What Is a Stroker Motor?by Dan Ferrell
The stroker motor has made it possible for many to realize their dream of a powerful engine at a low cost. Nobody said that you have to settle with the original horsepower in your Chevy, Ford, Chrysler or import. Increasing engine cubic inch displacement (CID), with the appropriate stroker kit, helps you get the extra power hidden within your original engine.
A stock engine can be rebuilt as a stroker engine by expanding engine displacement with the purpose of increasing horsepower. A stroked crankshaft increases the distance a piston has to travel up and down, which literally increases engine displacement or engine size, giving your engine the extra power without affecting your emission system or fuel mileage.
There are different ways to build a stroker engine. You can modify the rotating assembly--engine bottom end--or install a new stroked crankshaft, camshaft and related components for the cylinder block and head. This last alternative requires specific knowledge to obtain good results since cylinder reboring may be required in addition to other specific, calibrated engine parts.
A basic stroker kit usually includes a stroked crankshaft, main and rod bearings, piston rings and pins, and connecting rods. It is available in different materials--steel, titanium, forged or cast components--depending on application and customer needs. Also, specialized auto shops may have a variety of stroker kits, with replacement valves, rocker studs, lifters and oil pump included on optional packages. Still, another option is to buy a complete and assembled stroker engine for your specific car make and model, ready to install.
A stock car is set with an specific engine displacement at the factory depending on car weight. Horsepower is match to the vehicle's most adequate needed acceleration. This translates into an specific engine compression ratio. For example, if your car came with a 289 engine (289 cubic inch displacement-CID-engine), a compression ratio of 9.3:1 and 210 horsepower, you may be able to install a stroker kit to increase CID to 347, obtain a compression ratio of 9.8:1 and pull 390 of horsepower.
Modifying a stock engine with a stroker kit may have certain disadvantages. Since engine displacement is increased by making the pistons travel a greater distance and more rapidly within the same time frame as the original pistons to match intake and exhaust valves operating sequence, engine bottom end may wear more rapidly too.
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