Of all the parts that have come and gone for the small-block Mopar, none are as venerated as the fabled W-2. Due to the work of airflow master Bob Mullen, the W-2 was truly revolutionary when introduced in 1976. It put the small-block Mopar on the map as a serious race engine-serious enough to take the NHRA Pro Stock championship in 1979 when Ford notable Bob Glidden fielded a Plymouth Arrow for one year. It was eventually rendered uncompetitive in that venue via a rule change favoring large displacement engines. Does it have any relevance these days? Here's the bottom line; it was great then and it's great today.
Originally, there were a couple of different versions of the W-2 and even more part numbers today, which has lead to some confusion. The W-2 heads were originally offered in two versions: the econo head and the race head. The valve length was the difference between the two versions. The production Mopar small-block engine has always had a relatively short valve length for the port configuration, leaving minimal room for valvesprings. The stock-installed height was 1.65 inches, too tight to run a high-lift cam without coil-bind problems. The original econo head used stock-length valves and rocker pedestals cast in the stock location.
Iron heads are typically in a rougher state from the casting process than their aluminum c
For race duty, a longer valve was used to fit the longer springs as required with high-lift racing cams. Move the tip of the valve up higher and the rockers will also have to move both up and away inward due to the valve's 18-degree angle from vertical. To accommodate the requirement for a relocated valvetrain, the race W-2s came with the rocker pedestals milled off and utilized separate stands and offset shafts to get the rockers in the proper orientation. That was the only difference; the ports and everything else remained the same. All W-2 heads feature wide, oval intake ports, which means the intake rockers must be offset so the pushrods will clear. As a result, W-2 heads need special offset intake rockers.
A recent addition to the W-2 lineup is a long-valve econo version, which represents the best of both worlds. It takes the long valve such as the old race head and gives all of the above-cited advantages, but has the pedestals cast in the relocated location so the rocker shaft bolts on without the separate stands. These heads are sold by Mopar Performance under PN P4529995 for the 2.02/1.60-inch-long valve econo version. At a retail price of $349.88 each for the bare castings, we believe they represented a bargain for the serious Mopar racer or street freak, so we ordered a set from Westoaks Dodge. To fill them out, we also ordered Mopar Performance's long-stem W-2 valves in the production 2.02-inch (PN P5249195) intake/1.60-inch (PN P5249197) exhaust sizes. The long-stem valves were about the same price as the standard valves. Going in, the W-2 combo also requires the special offset rockers we already mentioned, a W-2 oval port intake, and special headers to mate to the relocated exhaust ports.
We took our W-2 heads to Westech with the idea of running some baseline numbers on their Superflow 600 flowbench, then pulling out the carving carbides to see how they respond to porting. The heads were pulled out of the box and mounted to the bench, and we had our first set of numbers: 244-cfm peak intake flow at .600-inch lift and 140-cfm showing at .600-inch lift on the exhaust (Tables 1 and 2, column 1). The numbers compared favorably to what we've seen for aftermarket small-block Chevy heads on this flowbench and way better than a stock 360 head's 194-cfm intake, 128 exhaust.
The most basic level of porting is to blend the machined area below the valve seat into th
To confirm our suspicions, the intake short-side turn was blended next. Lots to work with
Similarly, the exhaust short turn was blended (pointer), with just as dramatic a result. S