High-Performance Chevy Small-Block Cylinder Heads

Out of the many engine components that are crucial to building engine power, cylinder heads come pretty close to the very top of that list. High-Performance Chevy Small-Block Cylinder Heads taps into some of the best small-block Chevy head resources in the United States, then distills all the valuable port design and airflow management information. The book covers both Gen I and Gen II small-block Chevys, sometimes touching on the Gen III and Gen IV, and starts from the basics and works into more in-depth concepts to uncover all the nuances that make power in the small-block Chevy. The book is packed with sharp, detailed, close-up photos as well as tables and diagrams.
Book Excerpt: High-Performance Chevy Small-Block Cylinder Heads: Airflow, Rebuilding, Assembly, Porting, more SMALL-BLOCK RACE HEADS

There is probably no V-8 pushrod engine in the entire world that has more dedicated cylinder heads designed specifically for racing than the first-general small-block Chevy. A scant few decades ago, there was basically the iron Bow Tie head cast by GM and a few class-specific aluminum castings, and that was the entire race head buffet menu. Now well into the 21st century, you can't swing a dead camshaft without hitting a new small-block race head. You would think that Brodix damn near owns the race head market with its incredible array of 18, 16, 15, 13.5, and 12-degree valve angle heads aimed at the wild world of drag racing, sprint cars, and dirt track slammers. And as it turns out, valve angles are really the whole point of the race head market. Rather than get into the details of each cylinder head as we have in previous chapters, we're instead going to touch the wave tops, if you will, in order to keep this section brief. Frankly, if building race engines occupies your every waking moment, then most of what this book has to offer is of little application. Instead we look into what makes up a race head and why intake valve angle is such a big deal.

VALVE ANGLE

As we've stated before in various chapters in this book, the stock small-block Chevy valve angle is 23 degrees, but it didn't take engineers long to figure out that a taller, more vertical valve angle offered several advantages to improved flow. In addition to this rather steep valve angle, the stock valves were not located on the cylinder bore centerline. Instead, the OEM valve (and all subsequent versions of the 23-degree small-block head) are located over a quarter of an inch (0.275 inch) away from the bore centerline. At maximum valve lift, this off-center location places the valves closer to the combustion chamber and the cylinder wall, restricting potential airflow. For the small-block Chevy, the original race heads accepted for use in NASCAR stock car racing that first addressed this valve angle issue were the GM 18-degree heads. This move was quickly followed by a set of 15-degree heads, both of which are still available through GM Performance Parts (GMPP) in semi-finished configurations without seats or guides. Since then, several other GMPP heads have appeared that further complicate the issue, requiring us to go much deeper in detail than just a change in valve angles.

Subject: Transportation: Automotive: High-Performance: Chevy Small-Block cylinder heads. Rebuilding, assembly, porting, tips, etc. ISBN-10: 1613250630 | ISBN-13: 9781613250631 | CarTech SA125P