We don't have to tell you that other than a nitrous kit, the best bang for your horsepower buck will always be with a set of good cylinder heads. Dart recently upgraded its lineup of aluminum Pro 1 Ford castings with two sets of redesigned Pro 1 heads that have benefited from Dart's work with a very sophisticated wet flowbench.
This bench has allowed Dart to massage the ports to improve wet-flow performance, which means that the company now takes into consideration not just how the air flows through the intake ports and into the combustion chambers, but also how the heavier fuel is transported into the chambers. The theory is that by tweaking the intake ports and the chambers, these heads will make more power. It sounded good to us, so we decided to test the idea on a conservative little 0.030-over 302 Windsor Ford we put together for "Build Your First Engine" in the July '04 issue.
The only significant change we made to the engine was to swap in a larger cam to take better advantage of these new Pro 1 heads. Right about now, you're probably thinking that while these heads made great power, they're also probably close to $900 each. Would you change your mind if we told you these heads sell through Summit Racing for $456 each, complete and ready to bolt on? That's just a touch over $900 for the pair.
Head GamesDart offers two new Pro 1 wet-flow aluminum heads for the Windsor Ford-a 170cc intake port and a 195cc version. The smaller heads come with 1.94/1.60-inch valves. The larger heads are blessed with a bigger, 2.02-inch intake valve, while the exhaust remains at 1.60. Both heads feature 62cc chambers with a modern, kidney-shaped configuration to improve combustion efficiency. The heads lock into the standard Ford 20-degree valve angle and intake-face configuration, but to improve the exhaust side, Dart raised the exhaust ports 0.135 inch, although the stock header-flange bolt spacing remains. This means there may be some clearance issues between the chassis and headers in some applications.
The heads were assembled with 1.437-inch-diameter springs set up with130 pounds of seat pressure at an installed height of 1.800 inches. If you desire bigger springs, Dart can also equip either of these heads with 1.550-inch-diameter springs that pump up the seat pressure to a stout 195 pounds at a 1.900-inch installed height for more valve-lift clearance for the valve-stem seals.
Test ConfigurationTo complete our 306ci little-block, engine guru Ed Taylor bolted in a more aggressive Comp Cams Xtreme Energy 274 camshaft (see "Cam Specs" sidebar). While hardly a daily driver kind of cam, if you're going to build a serious small-block Ford, you have to screw a little camshaft into the engine. At a touch over 0.500-inch lift for the intake and exhaust, this cam and its longer duration seemed to be a good match for the Dart heads.
To complete the induction side, we retained the Edelbrock Performer RPM Air Gap intake manifold but added a larger Holley 750-cfm, 0-4779 mechanical-secondary fuel mixer to ensure the induction side would not present a restriction. We could have converted to a single-plane like an Edelbrock Victor Jr. 302 to pump up the top-end power, but we felt that the midrange torque advantages of the RPM Air Gap were well worth the small sacrifice.
With all this power potential, we knew we'd need a decent ignition system, so we plugged in one of Pertronix's new billet plug-'n'-play vacuum-advance distributors along with a set of Pertronix 8mm wires. The addition of the vacuum advance will also help part-throttle performance and also give a positive nudge to fuel economy, if you care about stuff like that. Then for the exhaust side, we bolted on a set of Hooker 151/48-inch Super Competition coated headers and plumbed the 3-inch collector into a 211/42-inch exhaust system using a pair of Flowmaster Super 40 mufflers.
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