Jim Smart
February 1, 2009
Compression is controlled primarily through piston dishing--the deeper the dish, the lower the compression. Compression is also controlled via piston compression height and how much volume there is above the piston. Combustion chamber size and gasket thickness also contribute to compression ratio.

Hot Six Performance
Building a powerful Ford six-shooter is a matter of getting back to old-fashioned hot-rodding basics. The more air and fuel you can huff into the chambers, and the higher you can tweak compression without harming the engine, the more power you're going to make. Nothing makes horsepower and torque like increased compression. These days, the most compression a street six can handle on pump gas is 10.0:1 to 10.5:1, depending on ignition timing, fuel mixture, and where you live (elevation, humidity, average temperature, and highest fuel octane rating available).

All 144/170/200/250ci cylinder heads are interchangeable. The main difference is valve and combustion chamber size. If you're seeking real performance from your Mustang six, it's a good idea to get acquainted with the 250ci cylinder head because of its bolt-on intake manifold. The 144/170/200 heads are limited from an induction standpoint because their integral intake manifold limits breathing potential. As you shop for a cylinder head, closely examine chamber and valve size.

As you might imagine, camshaft selection for Ford sixes is limited. However, look to Crane, Comp Cams, Clifford Performance, Clay Smith, Crower Cams, and Isky Cams for plenty of choices. There are also valvetrain options from Classic Inlines, such as roller rockers, one-piece pushrods, and dual-roller timing sets.

Classic Inlines offers a line of induction systems for vintage six-cylinder Mustangs. The bolt-on FSP-250-IMC intake for the 250 iron and aluminum head is designed for just about any kind of fuel distribution system imaginable, including carburetion and fuel injection. There are six fuel injection bungs for port fuel injection, or you can go with throttle-body injection. Classic Inlines also offers an FSP-250-IMW manifold for Weber carburetors or triple throttle bodies.

Pony Carburetors offers Ford six enthusiasts a number of options, including a new Autolite 1100 reproduction one-barrel carburetor. Known as the Vaporizer 1100, Pony Carburetors goes the classic Autolite 1100 one better with Annular Fuel Discharge for an improved fuel/air mix and better distribution. The result is smoother idle and better throttle response. Pony Carburetors also suggests 10-15-percent better fuel economy with the Vaporizer.

There's no excuse for a lame ignition system when there are plenty of options that eliminate points entirely, including the D.U.I. system from Performance Distributors. However, if you're on a budget, the PerTronix Ignitor II works wonderfully in an old Autolite single-point distributor, eliminating point-triggered ignition in 30 minutes. Opt for a PerTronix ignition wire set while you're at it.

Classic Inlines' aluminum cylinder head was designed to yield dramatic increases in horsepower and torque. Based on the Australian 250-2V cast-iron cylinder head, this new head is the result of extensive research and development. Classic Inlines' goal was to improve airflow to offer the most advanced aluminum head ever for Ford sixes.

Down Under Performance
There's a lot of street chatter about Australian Ford sixes. However, Ford six history Down Under isn't much different from that of North America. Early on, Australia and New Zealand got the same sixes as North America, and so did South America, with some variations in displacement. The game changer is what Ford Australia and South America did with this six later on. In 1976 Ford Australia fitted the venerable 250 with a new cast-iron crossflow cylinder head, which improved performance dramatically. This new crossflow design improved flow and also moved exhaust manifold heat away from the induction system. It may surprise you to know the crossflow head was a spin-off of the 351C head concept with the same valvetrain components and combustion chamber design.

In 1978 Ford Australia fitted the 250 with a new aluminum crossflow head for cleaner emissions and better performance. Instead of Autolite or Motorcraft carburetion, they got Webers. Bosch Jetronic Fuel Injection followed in the '80s.

The Aussie Ford 250ci six became an overhead cam design in 1988, yielding greater torque. The 250 was enlarged to 4.0 liters in 1991, and in 1998 Ford Australia made significant improvements to make the engine more durable, including larger main journals, cast aluminum oil pan, and variable valve timing. What's more, double overhead cam technology is coming for Australia's inline-six.