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Engine Boring and Engine Stroking Fundamentals

By , Photography by , Illustration by Crane Cams Inc., Patti Paulk, Steve Amos

If a clearance problem exists, either the crank counterweight or the piston can be remachined. Do not remachine the counterweight in a circular arc or there will be insufficient weight left for balancing purposes. Instead, the counterweight must be cam-ground for clearance by an experienced custom crank shop.

Con Rod Conundrums
Engines that operate over a broad rpm band (like acceleration engines or street engines) perform best with rod/stroke ratios in the 1.7:1 range. Engines that operate within a narrow rpm band (such as superspeedway, oval-track, or offshore racing-boat engines) like even higher rod/stroke ratios. As the stroke increases, the rod needs to get correspondingly longer to maintain the optimum rod ratio-but the longer the stroke, the less room there is to fit a longer rod. Too-short rods increase cylinder wall thrust-loading and restrict maximum rpm potential. Bottom line: On a big stroker, use as long a rod as you can get away with, based on the smallest practical piston.

Because of these complexities, leading aftermarket suppliers have developed integrated stroker kits. They have the experience to know what is or is not practical. Unless you're experienced in this area, it pays to consult a recognized expert like "Hank the Crank" (HTC). Yet, the payoff in added performance is worth the hassle-you can make the engine look stock on the outside, but pack it discreetly with additional displacement on the inside...and no one's the wiser until you blow their doors off.

SOURCES
Crane Cams
1830 Holsonback Drive
Daytona Beach
FL  32117
866-388-5120
http://www.cranecams.com/
HTC Products Inc.
10640 S. Garfield Ave.
South Gate
CA  90280
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