Tunnel Vision: Dual-Quad 557 Ford

By Richard Holdener

Tunnel vision can be described as a narrow focus, not unlike looking through the proverbial tunnel. As you might imagine, tunnel vision can be both productive and destructive, depending on your perspective. Oftentimes tunnel vision eliminates outside possibilities that may otherwise provide the answer to your dilemma. By contrast, the narrow focus can also mean you have applied all of your attention to the task at hand while eliminating unwanted distractions. Our tunnel vision is more of the later, and focuses on building a combination that deserved not only the massive tunnel ram, but also the dual 1050 Ultra Dominator carbs. In the automotive hierarchy, sometimes more really is better, as in more cubic inches, more compression, and certainly more head flow. As easy as it would be to perform this test on the more common big-block Chevy, we decided to make things difficult and selected a big-inch Ford. Despite offering the largest stock displacement of the big three (Chevy, Dodge and Ford), the 460 was still way too small to deserve a dual-quad tunnel ram.

In our quest to maximize power for our tunnel ram we needed several things, including the induction system itself (tunnel ram and carbs), plenty of head flow, and massive cubic inches. The cam timing would come into play to take full advantage of the available airflow, and work to shift the torque curve higher in the rev range, to produce the desired power peak. Toss in all the associated components to make it all come together, and you have the makings of one serious Ford motor. The build started with a production 460 block. Big as it was, 460 inches was not going to get the job done, so we decided to step up the displacement. Knowing that the 460 would accept a sizable increase in both bore and stroke, we combined a 4.440 bore with a massive 4.50-inch stroke. The result was an increase in displacement of nearly 100 cubes, taking our original 460 to no less than 557c.i.. For you modern Ford fans, that’s roughly equivalent to a pair of 4.6L Cobra motors!

Such a massive short block deserved (and required) quality components. The poked and stroked 460 2-bolt block was filled with a stout reciprocating assembly that included a 4.50-inch (4340) forged-steel crank and 6.70-inch (BBC) forged, H-beam connecting rods from Speedmaster. The crank and rods were matched to a set of forged flat-top Ross Racing pistons, designed specifically for the unique valve orientation of the TFS A460 aluminum race heads. It is important to note that the valve orientation of the TFS A460 heads differ from the stock and Super Cobra-Jet heads.

The first of the power producers applied to the sizable short block was a properly proportioned cam profile from COMP Cams. Knowing even the typical Saturday-Nite Special would not suffice, we selected a stroker-sized roller camshaft. Supplied by COMP Cams, the drag-race roller profile was sporting an .806/.763 lift split, a (nearly open all the time) 275/284-degree duration split (@.050) and tight 110-degree lobe separation angle. The race roller cam was combined with a set of COMP 836-16 solid roller lifters, matching double roller timing chain, and a set of hardened pushrods. The big-block Ford required 9.20-inch pushrods on the intake and 8.90-inch pushrods on the exhaust. Oddly enough, the TFS A460 heads worked best with a set of 1.71 roller rockers designed for a big-block Chevy rather than the more common 1.73:1 Ford Rockers.

With displacement, compression, and cam timing taken care of, it was time for some airflow. Topping the 557 stroker was a set of aluminum Power Port A460 race heads from Trick Flow Specialties. Impressive even in their Fast-as-Cast configuration (412 cfm at .800 lift), the TFS Power Port A460 heads were also available with full CNC porting. So we stepped up to the big set. How big you ask? The computerized porting process managed to whittle an extra 50 cfm out of the already impressive heads, with flow numbers peaking at 465 cfm at .800 lift. Ever the Achilles heel of Ford heads, the exhaust flow check in at an equally amazing 330 cfm. Since performance does not live by peak flow numbers alone, know that the porting improved the flow rate of the heads through the entire lift range. With huge port volumes it is easy to get big flow numbers, but the CNC porting only increased the port volume by 20 cc over the as-cast heads (340 cc vs 360 cc). Also, part of the flow package on the A460 heads was a stainless 2.30/1.88-inch valve combo, 83-cc combustion chambers (allowing a 12.5:1 compression), and roller valve-spring package that included titanium retainers, with the ability to swallow cams up to .850 lift.

What the stroker needed now was a suitable induction system. To feed the best, we selected an R-series A460 Tunnel Ram, also from Trick Flow Specialties. The TFS tunnel ram was designed with removable tops to accept either a single or dual Dominator carbs. We opted for twins on the tunnel ram, and then contacted Holley for a pair of their 1050 cfm Ultra Dominators. Like their R-series single-plane intake, the TFS tunnel ram was designed for a large-displacement, high-rpm Ford motor and even included bosses for nitrous and/or fuel injection. Not to knock a good fuelie motor, but how impressive is a big block Ford sporting a tunnel ram and a pair of shiny Ultra Dominator carbs?

For fitment, we installed an MSD low-profile distributor and crank trigger. Finishing touches on the 557 included a complete Moroso oiling system, ATI Race damper, and the usual Fel Pro gasket/ARP stud head-sealing system. Also present were plug wires and polished valve covers (to clear the COMP roller rockers) from Speedmaster, a Meziere electric water pump, and big-block Chevy headers to work with the BBC exhaust ports on the TFS A460 heads.

We were excited about getting the beast up and running, but we did so with care. The last thing you want to do is rush a build and cause damage before finishing the break in. After bringing the motor up to temperature, we filled the Moroso pan with 9.5 quarts of Lucas break-in oil and treated the 557 to a series of computer-controlled break-in cycles. After the break-in procedure, we performed an oil change and proceeded to tune the stroker, starting with carb jetting. The high compression deserved good fuel, so all testing was run on 100-octane Rocket Brand race gas.

After we dialed in the air/fuel mixture with the installation of 77 jets (all around), we then performed a timing sweep. The motor responded best to 34 degrees of total timing. With the tuning session complete, it was time to put the hammer down and see if our tunnel vision paid off. Tuned to perfection, the big-inch Ford thundered out peak numbers of 931 hp at 7,100 rpm and 757 lb-ft at 5,800 rpm. The exercise was a huge success, but we realized that exceeding 900 hp might be pushing the limits of the production Ford block. What this Tunnel Vision beast needed now was an aftermarket block, after all, we had a dual-Dominator, Big Shot NOS system capable of adding another 300 hp just begging to be installed!

Big-inch motors are awesome but strokers equipped with massive head flow, wild cam timing and a dual-Dominator tunnel ram are even cooler. Big torque is always a possibility with a stroker motor, but shifting that torque curve higher in the rev range means big horsepower numbers. Shifting the curve requires extra head flow, aggressive cam timing, and an induction system tuned for high rpm. The Tunnel Vision 557 had all of this thanks to the CNC-ported, Trick Flow A460 heads, COMP race roller cam, and R-series tunnel ram. Making sure the combo was fed an ample diet of air and fuel was a pair of Holley Ultra Dominators. Working in harmony, the combination netted 931 hp at 7,100 rpm and 757 lb-ft of torque at 5,800 rpm.