A plug with an extended nose...
A plug with an extended nose pushes the electrode farther into the combustion chamber. The more centrally located in the chamber the flame begins, the more efficient combustion will be. Just be careful to not create piston/plug clearance problems.
By choosing a longer plug that extends deeper into the cylinder, you move the electrode closer to the center of the combustion chamber. Now the flame front is more balanced as it extends (if only by fractions of an inch), and it can extend farther in all directions before meeting an obstruction. This causes the air/fuel charge to be burned more efficiently, which means more power.
Be aware that we are only talking about slivers of horsepower, but if you add up several improvements, you can get something significant.
If you have a choice, make sure to run racing-quality accessories on your engine. Most are already chosen for you as part of the crate engine package (fuel pump, water pump, etc.), but one usually open for improvement is the alternator. Simply getting rid of the alternator and depending on the battery is the best option, but that's usually only possible for four-cylinder classes. For V-8s and longer races, choose the smallest alternator with the least amount of output you can get away with. This will reduce the parasitic losses involved with turning the alternator. For more information on how limited amperage is enough when it comes to alternators, call a few manufacturers. Almost all of them have done testing with every conceivable combination.
We also wondered about drivebelt configurations that rob the least power. For more information, we turned to Rob Benson, who runs the dyno testing program at Hendrick Motorsports. Benson, who has tested both V-belt and serpentine belt systems, says he has found little difference between the two. His advice to racers is simply to keep using what you've got and save your money.
Crate motors are typically restricted by how much air they will flow through the heads. That doesn't mean, however, that other restrictions aren't also detrimental. For instance, stacking a restrictive stock air filter on top of the engine only compounds the problem. A stock paper filter is good at removing even the smallest contaminant particles from the air, but the cost is airflow. As a racer, you want an engine that makes the most power, not one that's going to last 100,000 miles, so go with the lightest, least restrictive air filter possible to keep the flow free and easy. Oil-impregnated fabric filters-such as those made by K&N-are made for racing and are usually the best bet.
On solid lifter cams, tightening...
On solid lifter cams, tightening the lash will make the cam act larger. Valve duration, overlap, and maximum lift are all increased.
The greatest restriction on the water flow through the engine is usually the water neck outlet on the engine. Most crate motors use a cast water neck, but if yours uses an AN fitting (or you can change out the cast piece), the standard size is 16. Upgrade to a size 20 AN fitting to reduce the restriction.
If you are allowed under the valve covers, adjusting the lash on solid-lifter-equipped engines is a good way to make a cam act bigger in nearly every important dimension. Closing the valve lash on a solid lifter cam causes the valves to open sooner and close later. This has the effect of extending the duration as well as the overlap period and increasing maximum lift by a few thousandths of an inch. The overall effect may be negligible-or even detrimental-at idle and low rpm, but at racing speeds, the engine's improved ability to ingest the air/fuel mixture should result in increased power.
On an engine with iron cylinder heads, you can usually get by with as little as 0.004 inch valve lash when the engine is hot. Aluminum cylinder heads are tougher because of the material's increased rates of expansion. A simple way of setting minimum valve lash with aluminum cylinder heads is to work with the engine cold. Close the lash until you can turn the pushrods with your bare hands. These guidelines should help you set the minimum lash possible without hurting your engine, but at these levels you need to show extra care to properly warm up the engine before stressing it.
Just like adjusting the valve lash, the following tip is dependent on your access to the front cover. If possible, you can advance or retard the cam- shaft to help tailor the engine's power curve to your track and driver. Advancing the cam one or two degrees typically increases bottom-end, or low-rpm, power while retarding the cam does the opposite. Again, we're only talking about small amounts, but when everything else is equal, every little bit helps.