Six-cylinder performance. Sounds like an oxymoron, doesn't it? But don't underestimate the humble Mustang six because there's a lot of performance potential. Pound for pound, the 170, 200, and 250ci sixes make more torque than a small-block 302 or a 351 V-8 because they have six cylinders in a row on a common crankshaft for smooth application of firepower. Inline engines-be they four-, six-, or even eight-cylinder-apply power more smoothly and effectively on a long, common crankshaft than V-type engines. The one big exception to this theory is four-cylinder engines, which struggle with vibration and harmonics issues, depending on the design
Inline-sixes were heavily drag-raced back in the '60s. In many parts of the world, such as Australia, they still are. Ford and Chrysler took inline-sixes to Daytona in the early '60s-Ford with the Falcon and Chrysler with the Valiant. Racers successfully spun these sixes to 7,000 rpm, making lots of power. Forty years later, that great potential for power still exists in these hearty powerplants.
The Mustang's 170/200/250ci six has its roots in the 144ci six introduced in the '60 Falcon. The 144 is a lightweight, gray-wall iron powerplant with six 3.5-inch cylinder bores and a 2.50-inch stroke along a four-main-bearing crankshaft. Ford took the 144's modest stroke and increased it to 2.94 inches to arrive at 170 ci for 1961. This made the little Ford six more crisp right off the idle circuit, getting Falcons and Comets off to a good start. When Ford introduced the Mustang in April 1964, the 170ci six was standard equipment, with 105 hp at 4,400 rpm. But journalists of the period weren't impressed with the Mustang's anemic standard offering. The 170ci six, coupled with a 2.77 unsynchronized three-speed manual transmission, was disappointing at best. The package simply didn't perform very well.
In 1964, Ford pumped up the bore and stroke to arrive at 200 ci. The 200's bore was 3.68 inches, with a 3.126-inch stroke. Externally, the 200 didn't look much different from the 144 and 170ci sixes it surpassed. That first year, the 200 had a four-main-bearing crankshaft and was available only in the Fairlane. A year later, the 200 would have seven main bearings and hydraulic lifters in a more rigid block. In August 1964, Ford began offering the 200 as standard equipment in the Mustang. The 200 was more peppy with 120 hp at 4,400 rpm. Torque improved dramatically to 190 lb-ft. In 1966, the 170/200's standard 2.77 crash-box was phased out in favor of the fully synchronized 3.03 three-speed "Top Loader" manual transmission.
In 1969, Ford raised the 200's deck some 1.66 inches, using the same 3.68-inch bore, and stroked the taller block to 3.91 inches to achieve 250 ci. What this meant for the little six was big-six torque, with 240 lb-ft of twist at 1,600 rpm. The 250ci six was a nice Mustang option in 1969-'70 for those who didn't want a V-8. From 1971-'73, it became the standard Mustang power offering. From 1974-'79, the venerable inline Ford six was dropped from the Mustang, returning for 1980-'82 as the 3.3L inline-six due to a critical shortage of 2.8L Vulcan V-6s.
At first glance, the 170/200/250ci sixes all look the same. Closer inspection reveals the differences. The 170ci six has three freeze plugs in the block. The 200ci six has five freeze plugs. The 250ci six is 1.66 inches taller than the 200ci six and is easily identified by its taller design and a four-bolt water pump. The 200ci has a three-bolt water pump. The 250 is 31/44 inch wider than the 170 and 200.
This is the 144ci six as it...
This is the 144ci six as it appeared in the '60 Falcon. It was a simple engine with a Holley glass-bowl carburetor, log-style intake and exhaust manifolds, and mechanical lifters. Shaft-mounted rocker arms were fully adjustable.
Look at what performance buffs...
Look at what performance buffs were doing with 144 and 170ci Falcon sixes in the early '60s. This one has a three-one-barrel Offenhauser setup with three Holley one-throat atomizers. A progressive linkage brought the two outer carburetors on line at wide-open throttle.
The 144 and 170ci sixes had...
The 144 and 170ci sixes had four main bearings. The 200ci six roared onto the scene with a supporting cast of seven main bearings. With seven main bearings and a good balance job, the 200 can spin to 7,000 rpm.
If you build your 200 six...
If you build your 200 six with all of the same kinds of modifications we make with V-8s, high-revving, snappy performance is possible. Good dynamic balancing, coupled with oiling-system modifications and the right selection of components, will get you screaming, high-revving performance. Hypereutectic pistons are enough for most street applications. Use forged pistons if you're going to spin it high for extended periods or with turbocharging or supercharging. The use of nitrous takes a lot of thought and planning.
This is a '65 200ci six cylinder-head...
This is a '65 200ci six cylinder-head casting with a fresh machining and valve job. Note the smooth deck, new valves, and clean surfaces. These are 50cc chambers. Chambers grew larger later to lower compression for civilized operation with low-octane gasoline. Hardened exhaust valve seats arrived in 1972 for reliable operation with low-lead and no-lead fuels.
At first glance, Ford light-duty...
At first glance, Ford light-duty six heads all look the same. This is a '60 144ci cylinder-head casting-a C0OE. Casting numbers and dates are important for identification. The earlier heads have smaller valves and chambers. Valve and chamber size increased with increasing displacement.
Ford Six Performance Basics
When you're building a Mustang six, it can get quite confusing when it comes to cylinder heads because they can all look the same. But there are clear differences you should be aware of. Here's how they stack up.
|Model Year||Displacement||Intake Valve Size||Exhaust Valve Size||Combustion Chamber Size|
|'60-'64||144 ci||1.467 in||1.266 in||44-51 cc|
|'61-'63||170 ci||1.522 in||1.266 in||48-53 cc|
|'64-'72||170 ci||1.649 in||1.380 in||48-53 cc|
|'64-'73||200 ci||1.649 in||1.380 in||51-53 cc|
|'78-'82||200 ci||1.750 in||1.380 in||62 cc|
|'69-'75||250 ci||1.649 in||1.380 in||62 cc|
|'76-'80||250 ci||1.750 in||1.380 in||62 cc|