Blown, Big-Inch Ford Windsor 427 Engine: Animal Unleashed

On the Dyno

When Vrbancic Brothers installed the engine on its dyno, a small number of runs was anticipated. After all, the carburetor-as are all Carb Shop carbs-had been given a test session on Vrbancic's big-block Chevy dyno mule to verify functionality and the fuel curve. The rest of the engine was not breaking particularly new ground for the Vrbancics. Of course, things got slightly more complicated. There was the monkey motion trying out different blower belt/sprocket combinations as we already related, then the original camshaft ended up with too much duration. In essence, the Vrbancics could see they didn't need that much cam to reach the power goal and, by shortening up the duration, more engine efficiency could be realized. Therefore a second Lunati mechanical roller was installed, with lift remaining the same, but the duration shortened from 265/276 to 262/268 degrees.

With the blower drive properly configured and the camshaft optimized, the engine was run naturally aspirated to give a baseline of the basic powerplant. As the dyno chart shows, even without the big ProCharger, this stroker Windsor was ready to rumble, blasting out more than 600 hp all by itself.

Then the supercharger was hooked up, and with every possible twiddle knob turned to "baby safe" mode the combination belted out 1,047 hp. By "safe mode," we mean the air/fuel mixture was a blubbering 9:1 down low and leaning out to just barely 11:1 at the power peak. While blower engines obviously make good power running a little richer than naturally aspirated engines, this is rich enough to ensure the 91-octane swill that passes for premium fuel in California would not detonate. In other words, it was putting out the fire with gasoline.

Also important to note is the water temperature was set to a frigid 120 degrees. Again, this is ridiculously cold to avoid detonation, and more power would easily be made simply by warming up the cylinder heads with 140- to 160-degree cooling water, which is more of a dynoing norm.

When run naturally aspirated, the cooling water was in the low-150-degree range, which did aid power compared to the blown run. Ignition timing was set at 31 degrees initial, with admittedly minimal retard-just half a degree per pound of boost.Just the same, the power is prodigious. The dyno chart starts at 4,500 rpm, where 599 hp and 699 lb-ft of torque are already on tap. This is with 7 pounds of boost measured at the carburetor, along with a fat 10:1 air/fuel ratio. More than 800 hp is available by just 5,500 rpm, 900 hp at 6,000 rpm, and 1,000 hp at 6,600 rpm. If this thing doesn't set you back in the seat, we don't know what will.

If you're wondering what the engine is like at lower rpm, look at the naturally aspirated data. There we see the engine opens with 306 hp and 459 lb-ft of torque at just 3,500 rpm-with zero boost, of course. Considering the blown engine is making 7 pounds of boost at 4,500 rpm, it's safe to assume it makes a couple of pounds of boost in the 3,000-rpm range. That's enough to up the power a little, so there's no lack of oomph down low. We'd say the only real issue here would be finding a tire and suspension that could hang onto this power.

What Could Be

With the engine set on double safe, it's interesting to conjecture on what the engine could produce if turned loose. There's plenty to play with-the coolant temperature could be raised and, obviously, the mixture could be leaned out. But the big gorillas are rpm and boost pressure. Note that the power peak was achieved at 7,000 rpm right at the end of the run. This engine is designed to run past 7,000 rpm, and simply turning it up a few hundred more rpm would deliver more boost and substantially more power. And, clearly, different pulley-and-belt combinations would deliver even more boost if anyone thought it necessary.

All of this is not to mention the benefits of simply running the combination on high-octane race gas, with all the boost and ignition timing increases that would allow. All told, this engine could easily whip out 1,300 hp with more aggressive tuning and boost in the low-20-pound range-something it could safely do with race gas, another degree of ignition timing, a jet change, and holding down the handle a few hundred more rpm. Wow!