Chevy's Bow Tie cast-iron...
Chevy's Bow Tie cast-iron head doesn't have the many options available that other manufacturers have in terms of runner sizes, but it is the standard all others are measured against.
Courtesy GM Performance Parts
There is a reason the majority of circle track race cars are Chevrolet based. The venerable small-block has been around forever, and there are so many aftermarket parts manufacturers for the engine that it almost becomes an embarrassment of riches.
All the same, those riches can become a bit confusing to the racer. You only want the best, but there are so many options available that it's nearly impossible to determine what combination from which manufacturer will be best for your needs. That's especially true when it comes to cylinder heads, which, along with the camshaft, hold the key to making power in any engine. To help you get a better idea of what's being offered, we rounded up some of the best options available from the most reputable manufacturers working today. For this article, we are limiting ourselves to heads most commonly seen in stock-level classes: small-block cast iron with as-cast ports and chambers and valves at 23 degrees. Aluminum heads and CNC ports will be a story for another day.
RHS uses its new Clean Cast...
RHS uses its new Clean Cast Technology, which allows it to hold its castings to extremely tight tolerances. One advantage is very efficient water jacket passages that help eliminate hot spots and detonation.
ChevroletAs a general rule, the only time you want to run a stock Chevy head is when the rules require you to run one. Nevertheless, that doesn't mean Chevy has nothing to offer-quite the opposite.
GM Performance Parts' performance line of engine parts are all gathered under the Bow Tie label. Chevy's Bow Tie cast-iron heads are now known as the Phase 3, which replaced the Phase 2 heads in 2000. Changes over the Phase 2 include more material for the machined rocker cover rail and universal spark-plug seats so that it will accept either gasketed or tapered plugs. The Bow Tie heads are purpose-engineered. Although they look similar to the original "Double Hump" stock heads, they are quite different. Thicker water jackets and a 0.300-inch deck provide extra material for porting and even rolling the heads to straighten up the 23-degree valve angle. All the other manufacturers compare their cylinder heads to these.
One advantage of working with...
One advantage of working with a company like Dart is that it offers complete machining of your heads, including high-performance valve seats. You can order a set of heads ready to be unpacked and bolted onto your motor.
Racing Head ServiceRacing Head Service, or RHS, as it is commonly known, is a familiar name to the racers who have been around for a while. RHS is a Comp Cams brand that had been dormant for many years prior to being revived just a little over a year ago. Since then, though, the company has come on strong with some quality products. One advancement RHS is pushing is what it calls its Clean Cast Technology. RHS's advanced casting process ensures that chamber and runner volumes, port-to-chamber surface transitions, water jackets, and related design features hold extreme tolerances. It also means that the as-cast ports exhibit some excellent flow numbers.
RHS's new Pro Action line of cylinder heads for small-block Chevys feature specially designed runners and combustion chambers to maximize volume, atomization, and velocity. Improved valveguide material yields tighter tolerances and extended durability. Pro Action SBC Cylinder Heads accept 1.550-inch diameter springs and standard style rockers and valvetrain.