Performance & Hotrod Business May '14

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52 n Performance & Hotrod Business n May 2014 PERFORMANCE A dding a form of forced induction (turbo- charger or supercharger) is a popular and tempting method of increasing horse- power. However, instead of blindly bolting on a forced induction system and tromp- ing on the pedal, first consider the internal engine components and their ability to with- stand the added power. Here we'll discuss the areas of the engine of concern in terms of suggested upgrades. The changes/modifications/upgrades men- tioned here won't necessarily generate any more power, but will allow the engine to live under the anticipated boost. While it's great to consider a bolt-on power booster, we need to add a bit of insurance to give the engine a chance to survive. While adding turbo or supercharger boost to the tune of, say, 8 to 10 pounds may not require an extensive rethink of the block, rotating and reciprocating assembly, higher boost levels (as well as extensive use of high-horsepower nitrous injection) may place enough additional stresses that can potentially wreak havoc on an otherwise unprepared engine. The old racer's adage "in order to finish first, you must first fin- ish" applies here. Main Caps If you plan to create additional cylinder pressure and resulting stress on the bottom end, start with reinforcing the main cap arrangement that secures the crankshaft. If you plan to pump horsepower up into the 400-hp range or beyond, you can add an increase in bottom-end strength by switch- ing from original cast iron main caps to steel billet main caps. Four-bolt caps are preferred. If the block was originally made with two-bolt caps, the block can be drilled and tapped to accept the additional two cap bolts per main location. If the block design permits, the use of four-bolt "splayed" main caps is ideal. This will feature the two center bolt locations ver- tically (90-degrees to the crank centerline), with the two outer bolt locations placed on Forced Induction By Mike Mavrigian Depending on the design of the block, four-bolt main caps may feature vertical bolt design at all four cap bolt locations, or may feature the outboard bolt loca- tions at an angle (called "splayed" cap design). The angled bolts provide added rigidity to better withstand increased stress. Engine Build Concerns For Learn why power enhancers are a solid investment. The use of a strong forged piston is mandato- ry for any serious forced induction and/or ni- trous application. This CNC machined piston from JE is a good example that provides both superior strength as well as reduced weight. It all starts with the block. If you have a choice (as when building from scratch), choose a block that features four-bolt main caps. If the block is to be oversized, prior to cylinder boring, mea- sure cylinder wall thickness to verify that you'll have enough wall material. Cylinder walls that are too thin can easily expand and even crack when exposed to high cylinder pressures. PHBMAY.indd 52 4/2/14 11:49 AM

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