Turbocharged Six Cylinder Ford Mustang - Inline Is Real Fine

Last month, we showed you Classic Inlines' approach to building a solid, streetable, race-ready Mustang platform for not a V-8, but a hot six-cylinder. Mike Winterboer of Classic Inlines decided to approach Mustang building as differently as he does inline six-cylinder powerplants.

This month, we're in Will and Kelly McLearran's race shop in Tucson, Arizona, to build a 273ci tall-deck Ford inline-six for Mike Winterboer's '69 Mustang SportsRoof.

Because six-cylinder buffs don't enjoy the same wealth of performance parts as those of us with small-blocks, it becomes much like building a V-8 in the old days. If you're building a hot six, you have to improvise-make the most of what you have, beat the bushes for parts, and build durability into your engine in order to keep it together. This isn't done by way of a stroker kit with a steel crank, and it isn't always possible to do it with brute H-beam rods either.

If you think building a six is cheaper than building a small- or big-block V-8, think again. Six-cylinder engines call for specialized parts, and your desire for big power may overwhelm your budget. Build a six because you like six-cylinder engines, not because you're looking to save money. This is all about the desire to be different.

But First, A Ford-Six Primer
Ford's lightweight, gray-wall, cast-iron six-cylinder engine first appeared in the '60 Falcon. It was a rugged, lightweight, fiercely dependable inline six-cylinder engine fitted with a Holley one-barrel, glass-bowl carburetor. Ford designed this engine with budget in mind. It was cheap to make and even cheaper to operate.

Manufactured in the Dearborn Engine Plant, where Ford also built FE-series big-blocks, the little Ford six was rather anemic at 144 ci and 90 hp. In 1961, Ford increased stroke, bringing displacement to 170 ci and horsepower to 101. In 1964, bore and stroke were increased again to achieve 200 ci.

At first, the 200 six had four main bearings, just like the 144 and 170. For 1965, Ford changed this engine's architecture, increasing the number of main bearings to seven for rigidity and smoothness. The seven-main-bearing block is easily identified by five freeze plugs on the right side instead of three with the 144/170/200ci four-main-bearing blocks. The seven-main-bearing block is always the best choice for performance applications.

For 1969, Ford increased block deck height by approximately 2 inches and stroke by 0.784 inch to get 250 ci from the hardy Ford six. Although Ford had fuel economy and improved torque in mind for this engine, it didn't achieve fuel economy. A 302ci small-block V-8 gets better fuel economy than the 250. But if you're read-ing this article seeking performance, you're not concerned with fuel economy.

The 250ci six has features that make it different from the 144/ 170/200. Aside from a taller, wider block, five freeze plugs, and a deeper pan, the 250 also has a four-bolt water pump and a small-block bellhousing bolt pattern. Mustangs and other Ford compacts equipped with the 250ci six have an 8-inch removable carrier differential instead of the smaller 7 1/4-inch integral carrier rearend with four-lug wheels.

Another issue facing the six-performance enthusiast is mechan-ical versus hydraulic lifters. This calls for two different types of rocker-arm shaft assemblies, along with the corresponding pushrods. Hydrau-lic lifters call for nonadjustable rocker arms and round-tip pushrods. Mechanical cams call for adjustable rocker arms and cup-style pushrods. What's more, you can't install hydraulic lifters in an early Ford-six block with mechanical lifters. The necessary oil galleys to feed the hydraulic lifters aren't there in the early four-main-bearing blocks.

Building a six calls for the same attention to detail needed with V-8s. Cylinder blocks should be sonic-checked before any machine work, especially if you're going to boost the mix with a turbocharger or supercharger.

Heads Up
Ford six-cylinder heads didn't change much over the long production life of these engines. In fact, all heads are interchange-able. For the engine to perform properly, however, you must con-sider chamber size as well as valve and port size. It gets even more complex with Ford South America and Ford Australia head castings, which are better than North America's. Because these engines remained in production longer Down Under than they did in North America, there are some pretty terrific head castings available if you know where to look. There are composite castings with removable intake manifolds as well as a crossflow head. Classic Inlines can give you insight on where to find them.

The greatest shortcoming of the North American head is an integral, log-style intake manifold. Ford did this for cost reasons, but this head breathes poorly, and fuel-droplet distribution is horrid. Some heads, as a matter of luck and casting irregularity only, do better than others. Most of them cause poor idle quality and stumble-both difficult issues to overcome.

If you're going to stick with a North American head, base your choice on casting number and dimensions. Check chamber size and design. Are the valves shrouded or unshrouded? What happens if you machine the deck and wind up with a smaller chamber? Which head should you choose for your six-cylinder project? We discourage the use of early Ford 144ci and 170ci head castings because there's nothing to be gained from them. Chamber size will help compression and theoretically gain power, but valve sizing and shrouding will hurt performance-in short, no gain.

According to The Ford Falcon Six Cylinder Performance Handbook, the best heads to use are '77-and-later 200/250ci castings as they have the largest valves (1.76/1.38 inches intake/exhaust). They also have hardened exhaust valve seats from the factory and don't require modification. Chamber size is ideal at 60-62 cc. The book suggests checking chamber size before committing to a casting. Intake manifold volume is also larger with this head.

For more information on this book or to order one, contact Dave Schjeldahl at 582 Safstrom Pl., Idaho Falls, ID 83401; (208) 523-2763; or check out www.falconperformance.sundog.net.

Building a Turbo-Six ScreamerYou've got to love inline-sixes to fully appreciate why Winterboer and the McLearrans possess such a serious commitment to these engines.

The McLearrans cracked the 10-second barrier by understanding how inline Ford sixes make power. Kelly's automatic turbo Falcon has been the acid test with blown engines, painful setbacks, and learning the hard way what works and what doesn't.

The McLearrans will show us how to build a solid, reliable Ford six that will make upwards of 350-400 hp using a carburetor, and Winterboer would like to do it with electronic fuel injection.

Dyno-Testing Facts
McLearran Racing dyno-tested the new Classic Inlines aluminum head on Kelly's 10-second Falcon sedan drag car with a turbocharged, intercooled 273ci six and a C4 transmission. Here's what happened at IA Performance in Tucson.

Kelly's first pass on the dyno using a North American iron Ford head with log manifold yielded the following results:

Will says air/fuel ratio was stable at 11:1 running on E85 Ethanol fuel with a 450-cfm Holley two-barrel carburetor. The improvement in torque on the second run came from a timing retard and increase in boost. Note that horsepower fell, yet torque increased. Torque is what matters most.

Here's what happened when the McLearrans installed the new aluminum head from Classic Inlines:

The common denominator is tuning and torque. Everything else remained the same except for a cylinder-head swap. The Classic Inlines aluminum head has given this 273ci stroker a broader torque curve on top of more horsepower and torque. This swap has yielded 40 hp and 64 additional lb-ft of torque. The McLearrans want to lean the mixture just a pinch to improve horsepower, in addition to 17 pounds of boost. A cam swap is also in the works. We'll keep you posted.

Other Ford-six buffs have noted even greater improvement in performance using a 500-cfm Holley, richer jetting, and ignition-timing tweaks. Much depends on camshaft profile, elevation, temperature, relative humidity, and good old-fashioned tuning know-how.

Because Winterboer has fitted his SportsRoof with a fuel-injected 273ci six-stroker, we don't know what to expect. When he puts this beast on a dyno, we'll bring you the results.