4) Dyno It
Once an engine is assembled and ready to run, almost nothing can compare with a good dyno session to make the most of the power waiting to be unleashed. Optimizing a combination is very difficult to accomplish by any other means, and a well-instrumented dyno and an experienced operator can help get the most of what you have. Dyno-tuning will typically aim at optimizing the fuel system and ignition. A well-equipped dyno shop will have equipment to monitor the air/fuel ratio, and the engine can be run under various loads and conditions as the mixture is recorded. Careful changes to the air/fuel ratio will optimize power and economy. The gains can be very substantial even on a completely stock engine, while dialing in a custom-built high-performance engine is the best way to be assured that the powerplant is delivering what it's capable of.
Part of the dyno tune should include finding the optimal ignition timing for peak power and massaging the timing curve for the best balance of economy and power while avoiding detonation. There is quite a range of expertise from shop to shop, so consider carefully and ask around to find the most competent facility in your area.
5) Camshaft Considerations
Nothing determines an engine's character in quite the same way as the camshaft, and few parts have such a dramatic effect on output. Camshaft technology has constantly progressed over the years, and the opportunity is wide open for improvements to output. Many enthusiasts are under the impression that an aftermarket camshaft equates to a raspy, nasty race-car idle and poor street manners. The fact is many of today's designs can offer much more power than the older stock sticks without the associated ill temperament. Older camshaft designs were comparatively slow in terms of lobe acceleration and velocity, necessitating long duration to achieve high-performance levels. Long duration rapidly deteriorates idle quality and vacuum, as well as low-rpm performance. A modern cam grind can offer substantially more power through higher lift and area under the lift curve without sacrificing driveability.
Even more improvement can be had by going with a modern hydraulic roller design. Hydraulic roller cams are standard equipment in most modern engines, and the major aftermarket cam suppliers can provide kits to retrofit this technology into popular older engines. Hydraulic rollers have proven durable in OEM applications, and can provide a broader power curve in an older engine. The advantage is in the higher velocity that can be built into a hydraulic roller cam's profile. Whether the decision is to go with an original-style flat tappet or a modern hydraulic roller, there is huge potential for increased power available here. Along the same lines, upgrading valvetrain components with quality aftermarket pieces like stiffer pushrods or roller rockers can measurably add to performance in a completely inconspicuous way. Aftermarket camshaft manufacturers can help you select a camshaft that matches your power and driveability goals.
6) Porting For Power
Looking for a seriously healthy boost in output but want to retain a totally stock appearance? Consider having the heads custom-ported. It's no secret that the fast track to big power is airflow, and the aftermarket is flush with high-flow cylinder heads to do the job. Even the best of the older factory heads are hugely disadvantaged compared to the modern offerings in terms of airflow capacity. That gap can be narrowed with custom head porting. Increased head flow produces power gains without compromise; the engine will idle and drive as nicely as with the stock heads, but it will keep pulling as the tach rises.
Porting is a job entirely dependent on the individual artist working the metal, but the experts can achieve airflow gains of 25 to 30 percent. On the other hand, incompetent work here can actually ruin a cylinder head. Select your cylinder head man based on proven results and reputation, not price.
Porting isn't limited to the cylinder head. Experts can also dramatically improve the stock intake manifold's airflow, and even the stock cast-iron exhaust. Other options on manifold work include the Extrude Hone process, an automated abrasive process that can be applied to the intake or exhaust manifolds. With no visual clues to give away the game, custom porting is a must-have for huge output in a stealthy package.
7) Consider Coatings
A technology that has enjoyed enormous growth in the last few years is performance engine coatings. Coatings can provide an increase in output and durability without altering one external detail of a stock-appearing engine. The three basic categories of coatings are thermal, friction, and oil shedding. Thermal coatings present a shield to heat transfer, slowing the movement of heat through treated engine components. Experienced engine builders can use this property to their advantage to produce power. Common applications of thermal barrier coatings include piston crowns and combustion chambers. This helps to retain the heat of combustion in the cylinder, where it can add power rather than being absorbed as inefficient heat loss. Thermal barriers are often applied to the valves, helping control the heat transferred to the incoming mixture and reducing the tendency toward detonation in the process. Even the internal surfaces of the cylinder head and manifold's ports can be coated, altering the thermal characteristics for greater power production.
Antifriction coatings can be applied to a variety of engine parts, reducing parasitic loss while adding insurance against engine failure. Piston skirts, oil pumps, and crank journals are just some of the components that can benefit from friction coatings. The oil-shedding coatings work to reduce windage by minimizing the amount of oil that will "stick" to a component such as a rotating crank or connecting rod. Even the OEMs are beginning to employ coatings for the benefits in durability and power in engines such as the Z06's LS7.