The new Dart Pro 1 aluminum heads come in both 170cc and 195ccintake-port configurations. While making good power, you can also get apair of these heads, assembled and ready to bolt on, for less than $925.
We don't have to tell you that other than a nitrous kit, the best bangfor your horsepower buck will always be with a set of good cylinderheads. Dart recently upgraded its lineup of aluminum Pro 1 Ford castingswith two sets of redesigned Pro 1 heads that have benefited from Dart'swork with a very sophisticated wet flowbench.
This bench has allowed Dart to massage the ports to improve wet-flowperformance, which means that the company now takes into considerationnot just how the air flows through the intake ports and into thecombustion chambers, but also how the heavier fuel is transported intothe chambers. The theory is that by tweaking the intake ports and thechambers, these heads will make more power. It sounded good to us, so wedecided to test the idea on a conservative little 0.030-over 302 WindsorFord we put together for "Build Your First Engine" in the July '04issue.
The only significant change we made to the engine was to swap in alarger cam to take better advantage of these new Pro 1 heads. Rightabout now, you're probably thinking that while these heads made greatpower, they're also probably close to $900 each. Would you change yourmind if we told you these heads sell through Summit Racing for $456each, complete and ready to bolt on? That's just a touch over $900 forthe pair.
The 62cc chambers fit either 2.02/1.60-inch valves for the larger 195heads, or 1.94/1.60-inch valves for the smaller 170cc-intake-port heads.These small chambers will give you just under 9:1 compression with aflattop piston, a 0.042-inch gasket, and a zero deck.
Head Games
Dart offers two new Pro 1 wet-flow aluminum heads for the WindsorFord--a 170cc intake port and a 195cc version. The smaller heads comewith 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 headsfeature 62cc chambers with a modern, kidney-shaped configuration toimprove combustion efficiency. The heads lock into the standard Ford20-degree valve angle and intake-face configuration, but to improve theexhaust side, Dart raised the exhaust ports 0.135 inch, although thestock header-flange bolt spacing remains. This means there may be someclearance issues between the chassis and headers in some applications.
The heads were assembled with 1.437-inch-diameter springs set up with130pounds of seat pressure at an installed height of 1.800 inches. If youdesire bigger springs, Dart can also equip either of these heads with1.550-inch-diameter springs that pump up the seat pressure to a stout195 pounds at a 1.900-inch installed height for more valve-liftclearance for the valve-stem seals.
The exhaust port on the smaller Dart head measures 65cc while its largercousin measures in at 75cc. In an effort to improve port flow, thestandard Ford port spacing remains the same, but the ports on both headshave been raised 0.135 inch.
Test Configuration
To complete our 306ci little-block, engine guru Ed Taylor bolted in amore aggressive Comp Cams Xtreme Energy 274 camshaft (see "Cam Specs"sidebar). While hardly a daily driver kind of cam, if you're going tobuild a serious small-block Ford, you have to screw a little camshaftinto the engine. At a touch over 0.500-inch lift for the intake andexhaust, this cam and its longer duration seemed to be a good match forthe Dart heads.
To complete the induction side, we retained the Edelbrock Performer RPMAir Gap intake manifold but added a larger Holley 750-cfm, 0-4779mechanical- secondary fuel mixer to ensure the induction side would notpresent a restriction. We could have converted to a single-plane like anEdelbrock Victor Jr. 302 to pump up the top-end power, but we felt thatthe midrange torque advantages of the RPM Air Gap were well worth thesmall sacrifice.