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Mopar Engine Build: Part 2

Kevin McNulty | Writer
Posted February 18, 2007
Photographers: Tim Jenkins

Functions And Theories Of Building

In part one of the small-block Mopar build, we briefed you on the high-quality Clevite components that were used in its construction. Part two of the build is an overview of assembly and machine work. There are literally thousands of factors that come into play when rebuilding any engine. So rather than attempt to cover each topic in depth, we will cover the basics and highlight those steps of most importance.

If you are looking for performance, reliability, and economy, then great care and consideration should be taken in all aspects of your engine build. It's a given that all engine kits, parts, machining, and builders are not equal. This is why we chose Tim Jenkins at DOA Racing to build our powerplant. His skills are beyond excellent and nothing short of phenomenal; his reputation as an engine builder is impeccable.

Correct and accurate machining and balancing on the rotating assembly is imperative if maximum power and performance are desired. Power losses and premature wear from an engine "fighting" itself are all too common. Parasitic losses can be lessened greatly, in turn freeing additional power. This is literally free horsepower. Our small-block Mopar has been balanced and blueprinted, stress-relieved, line-bored, decked, bore-located, and honed for our specific application. All holes were chased (cleans threads) not tapped (cutting threads). When something is tapped, material is removed, lessening the strength of the anchoring point. Blueprinting involves checking every tolerance, noting specifications, and eliminating the variances.

Stress-relieving the Mopar engine or any other small-block is important because it all but eliminates future core shift and settling. What this means is that machining a block, crank, and related components causes heating of the metal. In time, the structure and component will change in dimensions under usage. Usually a slight distortion occurs that is hard to replicate during machining. Stress relief is performed by heating the block and all internals such as the crankshaft, rods, and related components, then slowly cooling them over a period of time. This is achieved by lowering the temperature in set increments.

Line boring is to make certain the bores are aligned and the crank runs straight in the block. It's all relevant to angles. If disassembling a used engine, make sure the crankshaft's bearing caps are not moved out of the order from which they were unbolted. Do not mix and match the caps.

Decking the block and heads ensures correct alignment, a true flat surface, and a proper finish for gasket seal. This is why torque plates are used when boring - doing so duplicates loads placed on the block deck.

The crank has also been ground, phased, chamfered, and micro-polished. The rods were also stress-relieved, phased, straightened, and resized. New rod bolts should always be used. The Clevite pistons were a matched Clevite set that needed no work - they were balanced right out of the box. The moly piston rings were gapped, filed, and fitted for the intended usage. The high-quality Clevite coated bearings used were almost too good for this application and build. The parts are about as high-end as components get and more appropriate for a $100,000 race engine. You may refer back to part one of the build for further information on our Clevite parts.

When the crankshaft is phased it means that one journal (throw) is bottom dead center, and number two is at top dead center right down to the "degree." Phasing the crank ensures the throws are in their correct location during their cycles.


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Mooresville, NC 28117
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