I have been thinking about building a Cobra kit car, but with a twist. Anyone can build one with a big V8 engine, I am thinking of building one with an alternative choice for the engine. Knowing that the V8's are wide and challenge the cramped engine compartment for space, my idea was to use an Inline Six Cylinder engine in my car. The immediate advantage of a six over a V8 is the smaller engine will weigh a lot less and leave a lot more room for things like allowing the driver's pedal to be mounted straight in front of the driver rather than offset to the left as on V8 Cobras.
So if the engine of choice is to be an inline six-cylinder engine, which one should I use? There is a wealth of powerful inline sixes available and most all of them will fit easily into the Cobra's engine compartment. The choice of engine manufacturer will dictate the choice for transmission mounted just behind the engine. Technically it is possible to connect an engine from manufacturer "A" to a transmission made by manufacturer "B" but it would be a whole lot easier for me, the At Home Mechanic, to use an engine and transmission combination from one manufacturer.
If I were interested in a foreign inline 6-cylinder engine/transmission the three major contenders would be from BMW, Nissan and Toyota. Each makes a long line of beefy inline sixes that come with matching transmissions that could be adapted to the Cobra. BMW engines are legendary for their precision and performance, but frankly BMW transmissions are not up to the same standard as their engines. Plus the cost of BMW parts is enough to remind you why BMW is known amongst enthusiasts as standing for Break My Wallet.
Toyota's inline six-cylinder engine dates from the late 1960's and is proven for strength and reliability. But the port design of the Toyota inline six leaves a bit to be desired. Still the Toyota engine and transmission is a pretty good choice and readily available with parts not being terribly expensive. If a Toyota engine transmission combination were to fall into my lap I would have to seriously consider using it.
Nissan's inline six engine with a factory turbo is the power plant of the legendary Skyline coupe, which is available only as a right hand drive sedan. Never sold in the United States, American enthusiasts have slipped a few used examples into this country but they hardly are common over here. That is a very strong, well proven, engine and transmission combination that would be a natural to make the kind of power I am hoping for in a small light package. But the availability of those engines in the US is fairly slim, even with the importation of cheap used engines from Japan so I will reluctantly take this engine off my list of potentials.
This brings us to the list of domestic engines that I could potentially use. The Jeep inline six has been produced since the 1960's when it debuted as a Rambler engine. Reasonably well supported in the aftermarket, it would not be too hard to make it work for my purposes. Gm has a brand new inline six that it sells in its line of intermediate trucks and has been well received by the motoring press. But being so new I doubt that there is much aftermarket support for that engine and may be pricey to acquire. The older GM "Stove Bolt" six came in a variety of displacements and is reasonably well supported in the aftermarket. At one point this engine was judged to be the best American inline six in terms of power production potential and there was even an Over Head Cam version created by Pontiac back in the 1960's. If I were a rational guy I would give this engine and the wide range of good GM transmissions that easily bolt up to it serious consideration as the inline six that should go into my Cobra. But a GM engine in a Cobra is like suggesting serving a Honey Baked Ham at a Passover dinner; it just is not done. So as attractive as the GM inline six may be to those who wish to defy conventional wisdom with the greatest elan, I will have to take a pass on this idea.
This brings us back to the Ford family of inline six engines. Designed in the late 1950's at about the same time as the small block 260/289/302/351 family of Ford V8's, the inline six can claim to come from the same stable as the heralded engines that powered the original Cobra to initial glory. Two similar versions were created, a smaller inline six of 170, 200 and 250 cubic inches were built for the compact cars of the Ford line that began with the original Falcon and ran through the Mustang, Fairline, Maverick, and Fairmont models. A larger 300-inch version was intended for truck and van use. Dead reliable, cheap to build and cast iron strong the Ford inline six was a solid if unremarkable engine.
The Ford inline six was so successful Ford exported the design for manufacture by their subsidiaries in Argentina and Australia where the Ford Falcon nameplate is still a strong seller (although completely redesigned since the tooling of the original Falcon were shipped overseas for foreign construction). But there was one significant design flaw of the Ford inline six that the Argentines and Australians fixed.
The Ford inline six featured a rather rudimentary engine head. With both intake and exhaust ports on the same side of the head, it did not take advantage of the benefits of cross flow design. And reaching back to the Flat Head days of Ford engine design, the number three and four cylinders shared a common exhaust port. But maybe worst of all, Ford shaved a few pennies per engine by casting the intake manifold as part of the head casting. The intake manifold on a Ford inline six looks roughly similar to a 2" section of pipe that is cast parallel to the head with a small mounting on top for a tiny single throat carburetor. This head design endured for the entire American production run, but the Argies and the Ozzies ditched that design as soon as possible.
Both foreign versions of the Ford inline six soon sprouted home grown heads that featured a more conventional separate intake manifold and a reworking of the port design, although a cross flow head never emerged. Both the Argie and Ozzie head are a huge improvement over the US head and can be bolted to a US block with nearly no modification at all. That is the good news; the bad news is that the foreign heads are not commonly imported to the US. It is not entirely impossible to get a foreign head into this country; a company in Arizona, Ford Six Performance Parts (www.fordsixparts.com), will import you either type of head on an as ordered basis. And the good folks at Ford Six Performance Parts is making noises about designing and selling a cross flow aluminum head for the Ford inline six if there is enough interest.
So the plan for my Cobra would be to source a good foreign head to go on top of a 250 inline six block. Improving the induction a supercharger and fuel injection, a modern electronic fuel and ignition controller and higher compression will create an light, narrow inline six engine with Ford heritage that will easily make 300+ horsepower.
All of the power of a 5.0 V8 at about 150 less pounds. It sounds good to me. What do you think?