you intend to build engines on a regular basis, it’s a must-have item for the toolbox."/>
This Moroso crank dampener installer/remover is in my toolbox because it’s a true pro-quality tool. If you intend to build engines on a regular basis, it’s a must-have item for the toolbox.
This ARP crank bolt is a highly recommended addition to the fit and function of the dampener.
It is neither practical nor possible to rid the rotating assembly of all torsionals. But if those torsionals are reduced to some practical lower limit, you essentially eliminate any problems. Assuming the cam and valvetrain have inherently good mechanical dynamics, an effective dampener (compared to an indifferent one) can reduce the peak-to-peak torsional vibrations. On a 4.25-inch-stroke crank, this means a reduction from about 1.2 degrees to about 0.375 degree. Anything under about 0.4 degree is acceptable, but it is possible to make worthwhile reductions even on this figure.
Bear in mind that the longer the stroke, the lower the natural resonant torsional frequency. In this book, I typically deal with strokes between 4.25 and 4.75 inches. A really effective dampener can, with such stroke lengths, reduce torsionals that occur in the important 4,000 to 8,000 range to a peak-to-peak torsional vibration of as little as 0.2 degree. But to get that you must be very selective in your choice of a dampener.
Fig. 2.38. The ATI dampener is sold in several pieces. To minimize the effect of crank nose tolerances, the hub may require honing to achieve the desired fit to the particular crank being used.
Size and Weight
Engine builders have a strong tendency to focus unduly on dampener diameter and weight. The thinking here is that a lighter dampener, having less moment of inertia, allows the engine to accelerate faster so it must be better for performance. In 99 percent of instances, however, that proves to be not the case. The dampener attribute you should rank as number one, if optimizing performance on the track is the goal, is its ability to effectively dampen those unwanted torsionals. Everything else comes in far behind that requirement.
Although there are going to be instances to the contrary, my experience is that a good 8-inch dampener marginally edges out a 7-inch dampener in terms of engine output by the odd couple of horsepower for an engine in the 800-hp range, even though it’s typically 2 to 2½ pounds heavier (about 30 percent greater moment of inertia). My advice here is that for endurance applications go with a good 8-inch dampener.
The important weight/mass in a dampener is the inertial mass on the outside of the dampener. If you want to save weight and a little inertia, an aluminum hub is an option. However, my thoughts here are that the aluminum hub doesn’t take as many removals before the all-important fit on the crank becomes questionable. Remember, unless that fit is super tight the dampener does not work as it should.
Also, because I am on the topic of dampener retention, be sure to use an ARP crank bolt to hold the dampener in place: no exceptions here.
Dyno shops with torsional vibration test gear are virtually nonexistent. That being the case, how do you test the effectiveness of a dampener? Fortunately that is very simple. The more effectively the torsionals are dampened, the more horsepower the engine makes. I have spent quite a few hours doing torsional measurement but at the end of the day the best dampener is the one that delivers the best output.
Fig. 2.39. Both ATI and BHJ offer an aluminum hub option. This saves about 1½ pounds.
Fig. 2.40. Shown side by side, the difference between a 7-inch (left) and an 8-inch (right) BHJ dampener looks much greater than 1 inch. With longer-stroke builds (4.5 inches and over), the 8-inch dampener appears to be the best choice.
Balance
If you have made the decision to go with internal balance, you have addressed the number-one issue in the right manner. Also be aware that a little underbalance or overbalance does not affect how smoothly the engine runs. The biggest factor affecting just how smooth the engine runs is how close to uniform the weights of the rods and pistons are.
Fig. 2.41. BHJ manufactures professional-quality high-tech dampeners that are similar in design to conventional factory elastomer dampeners. These American-made custom-tailored dampeners have a very long service life capability and should be considered a top choice for a fit-and-forget application.
In a Chevy big-block, it’s essential to maintain not just oil pressure but also oil control. Controlling where the oil goes in the engine can be an issue even for a nearly stock engine turning moderate RPM. When the RPM climbs, this situation really demands attention.
What is done in the lube department on an all-out race engine can amount to 50 and possibly as much as 90 hp. The potential gain for a street engine taking care of business, even with mostly stock parts, is as much as 25 hp.
The first thing you need to deal with is oil pump selection. With a stock or even a pretty healthy modified unit, there is nothing to panic about as far as retaining reliability while utilizing a stock or nearly stock oil pump. However, that does not mean that there is no work to be done.
Fig. 3.1. This Moroso billet pump went on a 632-ci build equipped with Scat crank and rods and CP pistons. All this equipment was fitted to a tall-deck Dart block with Dart heads and intake. These top-quality parts are valued at a much higher level than stock, so the Moroso pump is cheap insurance for the investment.
The stock oil pump gets the job done on any engine that is good for 600 to 650 hp and 6,800 to 7,000 rpm. All you need to concern yourself with is that you bought a good stock pump and not a cheap offshore-produced item made to questionable tolerances. If the stock pump gets the job done, why consider alternative and most likely more expensive pumps? Although there are numerous answers to this question, the most obvious is that the more money you have in the engine build, the more sense it makes to better protect that investment. A number of oil pumps are available that provide both improved reliability and additional power.
Although it may come as a surprise to some, a Chevy big-block’s oil pump can draw well over 10 hp at 7,000 crankshaft rpm. Use a grade or so thicker in viscosity and that can go up another 5 hp. On the other hand, pay attention to the system’s efficiency and you can divert as much as 10 hp from what the oil pump absorbs and put that to good use at the rear wheels of your vehicle.
Wet- versus Dry-Sump Systems
If it is a question of which is best, a wet sump or a dry sump, dry is the way to go. Dry-sump systems provide better lubrication for max-performance applications. One of my favorite builds, done for a Lola T165 Can-Am car, was a dry-sump engine. But at the end of the day, I have to admit it was far from a budget unit and is out of the scope of this