For some applications, overt displays of power-enhancing changes are distinctly frowned upon. We're not just talking about the traditional "sleeper." For instance, many vintage musclecar enthusiasts go out of their way to keep their engine's appearance relatively "stock." In the realm of resto purists, parts such as custom manifolds, modern carburetors, or tube headers fly in the face of the goal of recreating the historically correct appearance. In these circles, anything giving away a "non-stock" appearance is unacceptable, and efforts to recreate the vehicle in its original glory are sometimes carried out to the point of fanaticism. Others might stray from total originality as long as the components resemble the factory equipment. Does a stock look necessarily count out the potential for performance augmentation? We would have to answer that with an emphatic "no." Buried deep within the engine's internals are opportunities for substantial power gains without giving away a clue.
A stock-appearing engine certainly can benefit from modern technology and advancements for very substantial power gains. The levels of this deception can be as subtle as the modification of selected original parts, or it can involve the substitution of production internals in favor of performance-bred replacements. The possibilities are nearly endless, and the prospects for power gains are truly enormous. We will detail some of our favorite little tricks, all of which are proven to substantially encourage output without offering a visual clue.
1) Crankshaft Capacity
This is perhaps the most flagrant violation of originality, yet it is totally discreet and offers one of the greatest opportunities for outright gain. Of course, we're referring to a stroker crankshaft. Increasing the crankshaft stroke will increase the engine's cubic-inch capacity in a way that's anything but trivial.
Aftermarket stroker crankshafts are readily available for most popular engine types. For instance, a 350 small-block can be readily stroked to 383 cubic inches, and those added cubes offer a pure increase in torque production. It's something to seriously consider at the time of an engine rebuild, and though no one will be the wiser, you certainly will be whenever the throttle is stood on end.
Employing a stroker will require a complete replacement of the engine's rotating assembly and often requires modifications to the block's crankcase to allow clearance. However, the popularity of this mod in the performance world has made stroker kits readily available, and the procedures are routine for most specialty engine shops. On the street, displacement rules, and with a stroker combination virtually any engine can benefit from a boost in size.
2) Winding Down Windage
While we're familiar with the resistance of air, one can only imagine the magnitude of resistance imposed as the crank struggles against the oil in the crankcase. In a running engine, a portion of the oil drains back upon the crankshaft, where it can become entangled in the crank's rotation, costing power. Further oil can be pulled up from the sump below, most significantly under the forces of braking, acceleration, and cornering as the oil sloshes around in the pan.
There are numerous steps that can be taken to both reduce the amount of oil snared by the moving crank and make the crankshaft slice more effectively through whatever oil is there. High-performance crankshafts are profiled on their protruding counterweights to improve their ability to cut through oil, directing oil away from the projecting rod journals and in toward the static main cap area. Quality aftermarket cranks can be had with nicely profiled counterweights, and even an original crankshaft can be modified in a similar way to reduce windage losses. Power gains on the order of 10-15 hp can be achieved at high rpm.
Other mods seek to separate the oil from the spinning crankshaft. Here we can employ windage trays, which separate and form a barrier between the crankshaft and the oil reserve in the sump. Baffling in the pan can also be added for similar benefits, helping with oil control under driving forces. Other tricks include using a crank scraper, a closely fitted sheetmetal projection mounted to the internal oil pan rail, which will "scrape" excess oil as the crank spins by. Further improvements can be had by controlling drainback in the center of the block by using standpipes, which allow for crankcase ventilation but direct drainback to the block's front and rear extremes.
3) Rings In The Power
Piston ring technology has improved dramatically since the old days. Neglecting these advancements is nothing short of ludicrous. Improvements can be found in materials, dimensions, and ring configuration. Considering materials, old-fashioned plain cast-iron rings wear the cylinder bore at a high rate, are high in friction, and are marginal in strength. Aftermarket high-performance rings made of ductile iron are a better choice. Ductile iron rings are more durable in demanding conditions and will take the punishment, whereas a brittle plain iron ring will break. Most of these high-performance rings are moly-coated, which greatly reduces bore friction and wear and aids ring sealing. No serious engine should be built with a lesser ring.
In the old days, standard-production engine compression rings measured 5U64-inch thick, which put a substantial amount of surface area in contact with the bores. The weak, plain cast-iron material relied on the high cross-section for strength. High-performance and racing engines would typically use a thinner cross-section of 1U16 inch, reducing friction and improving the ring seal at high rpm by virtue of a lighter and more reactive ring. Better ring materials made the 1U16-inch ring suitable for production, and now this ring width and even thinner sections are commonplace in OEM engines. In rebuilding a vintage engine, a 1U16-inch ductile iron moly ring pack should be considered the standard for increased power and engine life. In recent years, high-tech steel rings have grown in popularity, as have narrower 1.5 or 1.2mm or 0.043-inch widths, which are worth considering depending upon the application.