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.
EQ Cylinder Heads is a relatively...
EQ Cylinder Heads is a relatively new player on the market, but it offers a good quality racing head. It already has an official relationship with the IMCA, so you can expect to see a lot of these heads showing up on race engines soon.
Courtesy EQ Cylinder Heads
DartIn the good old days (which weren't really all that good), you always had to be on the lookout for block and cylinder head castings that may have looked good at first glance but suffered from power-robbing core shift. That's no longer a problem when dealing with specialty casting makers like Dart, which inspects every high-end race casting before beginning the machining process.
Dart's Iron Eagle line of cylinder heads have been a part of circle track racing for years, and for good reason: They make power. Standard features on these heads include bronze valve guides, multiangle intake valve seats, and hardened and radiused exhaust seats.
World ProductsWorld Products offers several lines of cylinder heads based on your needs. The S/R and S/R Torquer cylinder heads are designed as stock replacements and are even allowed by many sanctioning bodies for their Limited Stock classes since undamaged original castings are becoming increasingly difficult to find. Of course, World Products says the S/R Torquer cylinder heads offer a 30hp improvement over stock.
World Products has one of...
World Products has one of the most extensive lines of cylinder heads you will find anywhere. In addition, its Sportsman II line is specifically identified as legal inmany Street Stock rule books.
Courtesy World Products
The Sportsman II is the next step up and is one of the most popular cylinder heads in stock car racing. World's fast-burn combustion chamber design helps produce another 40 hp over the S/R Torquer line. Finally, there is the Motown Cast Iron, World's attempt at the best as-cast 23-degree Chevy small-block cylinder head that can be made. Large 220cc runners allow it to work best with large displacements or high-rpm engines.
EQ Cylinder HeadsEQ Cylinder Heads may be a new player on the market, but the company already has built a relationship as a sponsor in the IMCA. It also has an extensive lineup of 23-degree Chevy compatible heads. Features include Dura-Bond exhaust seats, a thick deck for angle milling, and a three-angle valve job. They arrive already machined for screw-in valve studs.