The research and development process for the MoTown heads consumed a year and a half of World's co-owner and chief "R&D" man, Gary St. Dennis', time.
"Moving, lengthening, or enlarging one set of ports can affect the others," Mitchell says. "It would have been easy to remove the heat riser, but because we wanted these heads to be street-friendly-and pass emissions testing-we had to be careful with the ports' design. Of course, they needed to flow well, too."
The MoTown 220 head carries a CARB exemption number, making it street legal in California-and everywhere else in the country. Since the new head fits the same engine family of the already CARB-blessed Sportsman II, getting the heads CARB-approved was a little easier. Basically, it meant running a car with the heads at an approved emissions lab. When the car passed, then so did the heads.
Because they are designed as drop-on replacements for production-style small-block heads, the MoTown 220 heads accept stock-type exhaust manifolds and require nothing unique to bolt them in place. The end pads will accept both early- and late-model accessories, while each head accepts either perimeter-style or center-bolt valve cover designs. (And because World Products is an OE supplier, its manufacturing process is QS-9000 compliant. This means the heads are built to OE-style standards.)
The World Products 415ci MoTown crate motor wears the 220 heads and is rated at 450 hp and more than 500 lb-ft of torque. The heads are a major reason for those impressive numbers.
"A big-inch engine needs to move a lot of air," Mitchell says. "These heads do it."
With figures like 450 hp and 500 lb-ft, he'll get no argument from us.
On the flow bench the Motown heads' intake port flows about 290 cfm at 28 inches of water, while the exhaust port flows 220 cfm. Not too shabby for an as-cast, un-ported head.
On assembled heads World employs Manley Race Master stainless valves. The standard size for the 220 head is 2.055-inch intake and 1.600-inch exhaust. World says a 2.080-inch intake valve will work, too, with a 1.625-inch exhaust valve for ported applications. Heck, if you leave the exhaust valve at 1.600, you could drop in a 2.100-inch intake valve. In comparison, the stock valve on World's Sportsman II heads is the already big 2.020-inch intake.
Like other heads, the 220 utilizes cast intake valve seats and hardened steel exhaust seats. Note here the bean-shaped combustion chamber, which gives the head its fast burn properties. The standard small-block chamber is more D-shaped. Also, the 220 has a maximum flat mill depth (up to the intake seats) of .040 inch.