Ford Small-Block Engine Parts Interchange by George Reid

Author:George Reid
Language: eng
Format: epub
ISBN: 9781613252796
Publisher: CarTech Inc.
Published: 2015-11-02T00:00:00+00:00

Ford’s Boss 302 was never intended to be a low- to mid-range RPM street engine. It does its best work at high RPM on a racetrack and was born for road racing. The Boss 302 head can easily be compared to the Boss 351 head with pushrod guide plates and screw-in rocker arm studs.

“Aftermarket” Cylinder Heads

The broadest selection of aftermarket cylinder heads really isn’t found in the aftermarket, but from the factory. Ford Performance (formerly Ford Racing and Ford Motorsport SVO) has offered the performance enthusiast many options. Selection isn’t what it used be because Ford Performance focuses on the Modular and Coyote engines today. Some of these time-proven heads are still available. Others have been discontinued and are available either used or as NOS in their original packaging.

The cool thing about Ford Performance aftermarket heads is the ease of selection along with their simplicity. You don’t have to search for factory iron castings such as 289 Hi-Po or 351W heads anymore. Ford Performance, or the used aftermarket, has a cylinder head for virtually every application.

The most common Ford aftermarket head is the GT-40 High Flow, available in iron or aluminum. If you want a more stock appearance that offers an improvement in performance, the GT-40 is a good choice. The GT-40, with good port, bowl, and chamber work, improves horsepower on the high end thanks to 1.840/1.540-inch intake/exhaust valves, which can be grown easily to 1.940/1.600 inches (Chevrolet intake valve size). The GT-40’s 65.5-cc chambers are a nice compromise between older 54- to 55-cc and 70-plus-cc chambers. You can mill this cylinder head’s deck surface to reduce chamber size and raise compression.

The GT-40 Turbo-Swirl cylinder head is now known as the M-6049-X306 and M-6049-X307 for 289/302/351W engines. The X306 aluminum head has a 64-cc chamber; the X307 head has a 58-cc chamber. Intake ports flow 240 cfm at .550-inch lift. Exhaust flows 170 cfm at .500-inch lift. This head is machined for 1.940/1.600-inch intake/exhaust valves.

Your pistons must have valve reliefs to reduce the risk of valve-to-piston contact. You must also check intake manifold port compatibility by doing a gasket match. The nice thing about the GT-40 head is its compatibility with just about any small-block intake manifold or header.

The Z aluminum cylinder head is a great alternative to the Turbo-Swirl for daily driving and weekend racing. Made of A356 T6 cast aluminum, the Z head offers improved flow numbers and more power if you give it your best attention. The Z mandates a competition valve job and bowl work. It is a CNC-ported head you can buy from Ford Performance. You get premium stainless-steel 2.020/1.800-inch intake/exhaust valves for more horsepower and improved mid-range torque. Beehive valvesprings eliminate valve float. Laser-cut guide plates yield perfect fit. Expect 319.7-cfm intake flow and 227.7-cfm exhaust at .550 inch.

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