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Mopar Engine Build: Part 2

Posted in How To on February 18, 2007 Comment (0)
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Photographers: Tim Jenkins

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.

The complete engine assembly was balanced to 0 grams by "Dyno" Don Henderson at Acts II in Statesville, North Carolina. Dyno Don also completed all other machining, and the headwork. Don has experience with the most demanding machining tasks, usually only working on higher-end builds.

Balancing is straightforward: The weights of the pistons, ring set, rods, and bearings are taken, then they are all matched equally in weight to one another. This doesn't mean that the weights of the pistons are matched to the weights of the rings. Basically, each matching component is matched weight to like components, i.e. piston to piston, ring to ring. The process of balancing the crankshaft includes adding or subtracting weight. The crankshaft is centrifugally spun, checked, and either drilled or ground (material removed), or welded (material added) for an even balance.

Overall, free horsepower is easily found in headwork. The castings used in common small-block Chryslers (SBC) are very poor and greatly reduce flow and performance. Our Mopar's heads were flowed at the lift being used, and port modification was decided upon on both the intake and exhaust. The primary work was performed in the bowl, seat, and exhaust port areas. The bowls (areas under the valve seats) are hideous in stock castings and constitute a tremendous power loss. Porting the bowls to 80 percent of the overall valve diameter will provide a marked increase in power. The exhaust deficit (due to overcasting) on stock heads in relation to intake flow is bad, really bad. The heads were ported to achieve a 15-percent variance. This means that our engine will not be hampered by restrictive exhaust ports not being able to flow.

A five-angle valve job is usually standard. A five-angle valve job means there are three angles cut on the valve face and two on the head. Our heads actually received a seven-angle cut: four on the valves, three on the seat. Tim won't give out the angle of the valve cuts because they are proprietary to the power and performance gains he achieves though his work.

New Clevite valve springs proper for this type of roller cam were installed, and high-performance locks and retainers were also used. A replacement roller cam (factory specs) and lifters were used. Again, a Clevite factory-spec camshaft was used because the usage (performance range) intended was so varied. Most of the roller camshaft grinds available vary widely in specifications. The possibility of using too aggressive a cam was clearly present with all cam grinds in relation to the ECU. Basically, a cam affects the ECU by changing the amount of vacuum, reversion, exhaust temp, pulse, etc. An unmodified ECU is slated to operate a "stock" engine and the anticipated set changes that engine sees in its usage. The use of an aggressive cam in some cases is too much for an OEM ECU and it can't cope. The cam would have added more power - probably much more - but the ECU might not have been able to manage the air/fuel ratio, and the engine would consequently run too lean or too rich.

When assembling an engine, it is important to be clear on one thing: correctness. This means getting your tolerances perfect. Do not assume anything or that "close" is OK. Do it right. Proper tolerances are the difference between a 100,000-mile engine and a 200,000-mile-or-beyond engine. Small-block Chrysler engines can be tricky. Check and then double-check again!

Some builders make the common mistake of assuming all is perfect and ready to go right out of the box or directly from the machine shop. Other problems arise when parts are cleaned improperly (this goes for new parts too). Do not forget to double-check all tolerances, fitment, gaps, and endplay. Thinking you can just bolt parts together can lead to disaster.

Trying to cut corners to save a buck or two may lead to more trouble than it's worth in savings. This is especially true if you are concerned about engine longevity, performance, and dependability. Short cuts and inferior parts usually leave an engine builder wishing he had gone the extra mile literally.

A good-quality treatment like Torco should be used on all bearings at assembly. You can also use Torco as ring lube. Antiseize should be used for heat-related fasteners. Using plenty of good-quality oil during assembly doesn't hurt either.

The break-in period is 1,000 miles. This means light usage at varied rpm with no towing. The rings need to seat, and parts must go through their natural facing process (break-in). Letting bearings go through hot and cold cycles allows them to correctly wear in. Don't use synthetic or paraffin-based motor oils for the first 1,000 miles.

Proper tuning is first and foremost among performance considerations. Everything else is dominated by the ECU. Short cuts like aftermarket items not suited for the job should be avoided at all costs. Another common mistake is a pro builder thinking he's better than he actually is! A final hot tip for engine building: Be patient, do it once, and do it right.

As we explained in part one of the small-block build, we chose Don-A-Vee Chrysler and Jeep in Placentia, California, to install the engine. The dealership has been the state's leading Chrysler/Jeep dealer since 1961. Don-A-Vee has a rich history in the off-road motorsports industry. Don-A-Vee has built Jeeps for the World Expedition Team's in Patagonia and fielded one the greatest desert race teams in history with drivers Curt Le Duc and Darren Skilton. Don-A-Vee has sent teams to the World Cup All-Terrain Rally series in Morocco, Spain, and Portugal, and it has also been a big part of Jeep Jamboree for over 15 years.

Don-A-Vee's technicians have experience in all aspects of Jeep vehicles. Gary Grinkevich is an expert on Jeep engine swaps and is recognized as one of the first people to ever perform a Cherokee/Chevy 350 swap. Gary is the heart of the Don-A-Vee staff, all of whom have had a part in building and maintaining the globe-traveling vehicles that come out of the shop everyday. Two of these Jeeps finished the London to Sydney Rally, and another traveled from Moscow, crossing Siberia, to the Pacific.

Don-A-Vee is also well regarded in the aftermarket industry. It has been involved in the development of aftermarket parts and accessories and even produces its own accessories, one of which is the famous Grand Cherokee rear tire carrier.

Sources

DOA Racing
Mooresville, NC 28117
704-799-6261
http://www.doaracingengines.com
Don-A-Vee Chrysler And Jeep
Don - A - Vee Chrystler and Jeep
www.donavee.com
D O A Racing

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