While the Mustang has always been revered for its V-8 performance, even today the base six-cylinder engine far outsells the V-8 model. The 200ci inline-six, first offered in the Fairlane as a four-main-bearing base engine, found its way under the hood of the new '65 Mustang as the base engine (replacing the smaller 170ci inline-six). By that time, the engine block had been recast as a seven-main-bearing unit to dampen crankshaft harmonics, making it one of the strongest inline-six Ford bottom ends ever built. These seven-main-bearing 200ci inline-six engines are smooth-running, easy-to-maintain torque builders that get the lightweight Mustang moving with little fuss. However, today we must deal with 80 mph highway speeds, $4.00 a gallon gas, and long commutes, all of which the small-six isn't well suited for. Giving the inline-six some oats means easier, safer merging with highway traffic, more power for maintaining those speeds, and simply making the vintage Mustang with inline-six power more fun to drive.
Thanks to our in-house Dynojet dyno, we were able to obtain real world numbers for Brian’s
Adding performance upgrades to the inline-six is the same as the typical V-8 performance enhancements of increasing airflow through the engine. If you remember your basic auto mechanics 101, an engine is simply an air pump. If you get more air into the engine (along with the required fuel needs) and get that air out of the engine faster, you will make more power. Typical upgrades such as a performance camshaft, larger diameter exhaust/headers, and basic tuning of the ignition timing and fuel metering all help. Unfortunately, Ford's third generation small-six was designed with an integral cast “log type” intake manifold that suffers from thermal encroachment, poor distribution, and no easy way to improve the air flow (you can't easily port it). Major machine work to add multiple carburetion or a larger single carburetor is an option, but does not address the short comings of the stock cylinder head design.
Classic Inlines has been over every inch of Ford's third generation inline-six engines to learn what makes them tick and how to extract reliable street and strip performance. Ultimately, Classic Inlines' Mike Winterboer knew that in order to keep the inline-six flame burning, an aftermarket cylinder head with improved airflow (including a separate intake manifold) was needed. Mike turned to the Australian Ford market, where inline-six engines are the norm and big power is available right on the showroom floor. The Classic Inlines aluminum cylinder head takes many cues from the Australian 250ci 2V head with a few tweaks here and there.
Some might ask why Classic Inlines didn't design a cross-flow head. Mike's answer is simple—cost. Not just the cost of the head itself, but of all the ancillary items that would be required (valvetrain, valve cover, distributor, etc.). With his 250ci 2V-based design, all existing valvetrain and other hardware bolts right on, saving users money.
Classic Inlines offers its aluminum head in several stages—from bare casting to fully assembled with race-level port work. To complement its cylinder head offering, Classic Inlines has put together a catalog full of valvetrain parts, internal engine parts, and more, many of which are custom-made just for them. You'll find everything you need to build your inline-six from street performer to all-out race engines at Classic Inlines, and that's why Mustang owner Brian Stilwell has been buying parts from them for his '65 hardtop since he purchased the car a little over two years ago. Starting with Classic Inlines' dual exhaust and header kit and moving up to its Weber carburetor conversion, Brian has been saving his pennies as a firefighter to take his 200ci powered hardtop to the next level.
Brian reached out to us (he's in our local Mustang club) and asked if we'd like to tag along for the build to observe the transformation. We jumped at the chance to give our six-cylinder readers some love and even had Brian bring the car to our Tampa tech center for some before and after dyno sessions so we could see firsthand what the improvements meant to the inline-six community.