Mini Stock Race Engine Tips

Mini-stock racing is an entry-level form of auto racing that typically takes place at local short tracks throughout the country. The series is popular with drivers because of its affordability--rules are designed to keep racing affordable, including typically only allowing four-cylinder engines. But drivers are always looking for ways to improve their performance, starting with getting the most horsepower out of their motors. These modifications fall into the guidelines of many mini-stock classes throughout the country; check with the rules at your local track before making any changes to your engine.
Reducing the weight of your crankshaft is one easy way to increase horsepower--a lighter crankshaft allows reciprocal parts to move faster by having less rotating mass to create resistance. This can be accomplished by shaving the counterweights to make them lighter. The counterweights are part of the crankshaft and help to reduce vibrations caused by imbalances. While they are still necessary for race cars, you will likely be less concerned about a "smooth ride" in your mini-stock car as you would be in your passenger car.
Piston Rings
Reducing horsepower lost because of friction is a major difference between a good engine and a race-winning engine. One way to reduce friction within the engine is to reduce the size of the piston rings, which seal the combustion/expansion chamber along controlling oil flow and consumption. Moving from the standard rings found in stock 2.3-liter engines most commonly used in mini-stock racing to smaller, thinner "metric" rings used in import cars will reduce the tension on the rings along with overall friction. Because the rings will not be sized exactly, it's important to hone the cylinders to the new rings in order to ensure a proper fit and seal.
Rod Journals
The rod journal is the interior part of the connecting rod that links the engine's pistons to the crankshaft. While many domestic 2.3-liter engines use rod journals that are more than 2 inches in diameter, some import cars like Hondas use 1.888-inch diameter rod journals. This difference has two purposes--it creates less friction in the motor by speeding up bearing speeds and also reduces the overall mass at the connection between the pistons and connecting rod.

When using a small rod journal, some of the issues that surface in other forms of stock-car racing, such as potential for parts failure, are not as pressing when it comes to mini-stock car racing. The mini-stock cars produce significantly less horsepower than other type of stock cars, lessening the stress on individual parts.

References:- Mini-Stock Racing - Go-Fast Tips for Mini-Stocks Project Mini Stock, Part III