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Finally! A Performance Cylinder Head for Ford Six-Cylinders
Six Power: The first look at Vintage Inlines’ new aluminum six-cylinder head
Since the first Mustangs and Falcons were purchased secondhand, gearheads have been pondering whether to build up the straight-six workhorse economy engines or swap out the six in favor of a V-8. The complexity of the conversion to V-8 power, while much easier in the ’60s cars, was still a little much for some, and the performance upgrade parts for the six-cylinder were sporadic at best. Plus, there’s something to be said for being different and building a smooth-running six-banger.
While there is a six-cylinder performance group today, their part selection has been a blend of old 1960s tech and parts that appear and disappear on a regular basis. One of the reasons for this is very simple: the straight-six was simply not designed for real performance. It was designed to be an economy workhorse that provides reliable day-in and day-out effort getting the small vehicles to and from their destination. They are proportionally heavier than their higher-revving V-8 cousins, with stout blocks and bottom ends that are bulky because Ford didn’t need to shave tenths off at the track. The biggest downfall of the six-cylinder was the head itself. With its cast-in uneven port length cylinder head and center exhaust outlet, it was clearly designed for ease of manufacture and not for any kind of performance use. Until now.
Vintage Inlines from Detroit, Michigan, has finally made available an aluminum cylinder head for the inline-six that will really open up these engines to the performance world that was not there before. The story about how this cylinder head came about is fairly long. Mike Winterboer was the owner of Classic Inlines, a company that specialized in six-cylinder performance. He had worked in developing an aluminum head down in Australia, with the intent of bringing it to the States. Mr. Winterboer passed away in 2015. He did finish the project, but it is unknown how many were available or sold. With his passing, a large force behind the six-cylinder performance movement faded.
Enter Matt Cox and Vintage Inlines. Matt is a long-time six-banger enthusiast and was able to acquire some of the inventory and items from Classic and keep the flame going. Although the tech was acquired, getting foundries to work with you can sometimes be a challenge. There are all the issues with working on something new and working it to make it a viable product. Matt was able to contract with the original foundry, and even though there were a few “relearning” issues, they were able to produce the cores. We have all seen press releases about a new product that turns out to be a fishing expedition and doesn’t really exist. Vintage Inlines has stuck to it and has succeeded, and the stack of heads on a cart during our visit was proof that this is for real and a huge leap forward for the inline enthusiast.
The Vintage Inlines head is based on the Australian 250-2V head, which came with a detachable intake manifold, the single most important improvement to the cast-iron originals. The intake ports were raised in the head to provide better flow to the larger valvetrain. Weight savings is nearly 50 percent, with the stock head checking in at 46 pounds and the Vintage head at a svelte 26 pounds. Care was taken to allow for stock components like valve covers and rocker arms, and even the stock exhaust manifold to bolt up to the head. The only thing that was changed was the water temp sender, and that the head uses ARP head studs to attach the head to the block.
With the detachable intake design, you now have a means of running a much more balanced intake arrangement. The original ran along a single pipe and dumped into each port. Right angles are bad for flow, and the center cylinders flowed much easier than the ones on the end, which took a much longer path. In the ’60s Offenhouser designed a 3x1 barrel carburetor setup that is still available today (Vintage Inlines part number OFF-200-3X1) that attempted to curb the problems of end cylinder starvation, and it does work somewhat. Adapters for two- and four-barrel carburetors are also available, but they don't get around the inherent problems of the flaws in the cast-in intake.
Vintage Inlines sells a spider-style, bolt-on intake designed for a standard four-barrel carburetor to mate specifically with the alloy head with a much smoother sweeping runner design to even out the flow to the outer cylinders. They have also installed fuel injection bosses on the tops of the raised intake port, making sequential fuel injection a reality. The stock Australian mounting points mean specialty goodies from Australia, like Weber carburetion, are also possible, and stack injection is a very easy fabrication.
The stock head has an open chamber design that varied between 52 cc to 62 cc in size. Coupled with dished pistons it didn't make much compression. The new heads are a closed-chamber design with chamber size of 55 cc. Coupled with a flat-top piston this will make a compression ratio in the range of 9.3-9.4 to 1.0. Perfect for today’s watered-down fluid we call “gasoline.” Vintage leaves plenty of material available for unshrouding of the valves and increasing the chamber size if desired.
Stock intake valves ranged from 1.680 to 1.750, and the exhaust remained constant at 1.380. Vintage has boosted the intake up to 1.800 with an optional 1.840, and the exhaust is increased to 1.500. Stock 289 heads came with 1.780 and 1.450, and 351W came with 1.840 and 1.540, a healthy upgrade to the original six-cylinder arrangement.
Another big detriment to the stock heads was the exhaust ports. The center two exhaust ports came together in a Siamese configuration, probably for no other reason than to make it cheaper to manufacture. This big space not only allowed for pressure differences between the center ports and outer four ports, it allowed for additional heat to be retained in the area right under the carburetor, heating up the fuel and causing some warping problems with the head. Aftermarket spacers were devised to solve the problem with the stock heads, but the aluminum head has been cast to eliminate this problem entirely. Ports are healthy and still have enough material to port-match to your headers. As noted before, the awful stock exhaust manifold single outlet will actually bolt up to the cylinder head, if you found yourself having to do that.
Since the six-cylinder was an economy engine, it was fitted with single-coil valvesprings and those not-for-performance two-piece retainers. The new heads come with a choice of a single spring with a damper or a dual spring, depending on your application, and Clay Smith one-piece spring retainers. The bigger valves are Port Flow stainless and the heads are fitted with steel valve guides. The head is designed to be compatible with the stock rocker arm shaft and rocker arms, but can be fitted with full roller rockers should the need call for them.
The heads are now being cast on the West Coast and are being shipped to Automotive Machine, in Fraser Michigan, for all the machine work needed to prep them for sale. Just like any other aluminum head, an engine builder can massage these heads for even more performance, with the exception of the area around the valvesprings. This has been optimized for full use of the newer springs. As mentioned before, all your stock or aftermarket goodies like headers, valve covers, and chrome goodies will come right off your old engine and bolt to this one.
As far as performance, the ball has just started rolling on the new heads and they are being delivered. It is not unheard of to make 500 horsepower with all that typical inline torque, and there is a car currently running in the mid-10s with this head and turbocharging—so real performance and even more potential future performance is in your hands. Before you start looking at that list of items to swap a V-8 into your Mustang, take a good look at the new Vintage Inlines aluminum cylinder head for your sturdy six. It gives you all the benefits of the V-8 and inline-six combined.