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Flow Test Of Small-Block Engine Heads
Sorting Out Performance Cylinder Heads
It's hard to believe today that just a little more than 10 years ago, small-block Ford engine builders went to great lengths to locate suitable cylinder heads for performance applications. There was the inevitable search of junkyards and swap meets for the popular '69-'76 351 Windsor heads, with their slightly larger intake ports and valves combined with 60.4cc combustion chambers for good compression. Or, with easy-to-find 289/302 heads, countless hours were spent in the machine shop for porting and polishing work, three-angle valve jobs, and port matching, all in the quest for just a hair more airflow. In the most extreme performance applications, builders opted for the huge ports of the 351 Cleveland heads, a swap that required different pistons, water passage modifications, and a special intake manifold. In short, the performance potential of the small-block Ford was limited by the availability of suitable performance heads.
That all changed in the late '80s when Ford Motorsport, now known as Ford Racing Performance Parts, released its aluminum GT-40 heads. With the popularity of the late-model 5.0 Mustang ramping up, other manufacturers--like Trick Flow Specialties, Edelbrock, and World Products--quickly followed with their own versions of high-flow, small-block Ford heads. Best of all for vintage Ford owners, the new heads bolted right on top of 289, 302, and 351 Windsor engines, so all of a sudden we went from digging through junk yards for suitable factory heads to scratching our noggins trying to figure out which brand-new, high-flow, lightweight aftermarket head was the best for our particular application.
Obviously, the modern heads flow more air than the vintage, cast-iron, small-block heads. To find out exactly how much more, we went to noted Ford engine specialists Powered By Ford in Orlando to set up a small-block head comparison test on PBF's in-house SuperFlow flow bench. Our baseline was the everyday 289 head, followed by tests of the 289 High-Performance head, which is essentially the same as the regular 289, and the former small-block champion, the 351 Windsor. As a benchmark, so to speak, we also thought it would be interesting to throw in a pair of Cleveland-style heads, including the four-barrel version with its huge ports and valves. Finally, we tested two of the more popular late-model aluminum heads: the Ford Racing Performance Parts' Turbo Swirl GT-40 street head and the more race-like Edelbrock Victor Jr. PBF had all of the heads, unported and unmodified, on the shelf, so all we had to do was gather them up for photos and testing, as performed by PBF's Dan Moffis.
For information on specific heads, click on the sidebars below.