Nothing screams '60s-era coolness like a bunch of velocity stacks on top of some American iron. Usually, they showed up on road racing cars where a mile-long torque curve could help the wide rpm ranges those cars saw.

Setting up multiple carbs on individual velocity stacks is, at best, finicky, and at worst, infuriating. It can be a tough chore to get multiple carbs dialed in to work correctly in unison, and keeping them that way can be even tougher.

So while Car Crafters have almost universally admired the look of multiple velocity stacks, it's never really caught on because it simply hasn't been worth the cost and trouble. However, we're now living in a golden age of horsepower thanks to advances in electronic fuel injection and computer-controlled engine management systems, and one of the benefits is some really cool velocity stack induction systems with modern electronics hidden inside.

Although the company has been known for years for their excellent-sounding exhaust systems, Borla has now also gotten into the induction side of the game with several throttle body kits for different engines in the Ford and Chevrolet families--and there are even options for Mopar owners with modern Hemis. Most of the kits feature billet machined air horns, high-volume fuel rails to feed lots of horsepower, an integrated fuel-pressure regulator and a trick billet throttle linkage setup. For those looking for classic looks, some kits mimic an old-school Webber carburetor eight-stack setup with cleverly hidden fuel rails and throttle bodies.

We've wanted to see out these induction systems in action, so when we heard that our friends at Prestige Motorsports in Concord, NC were building a 427-cubic inch Windsor with Borla stack fuel injection, we set up camp in their assembly room. Regular readers of Car Craft may remember that we recently worked with Prestige on an extensive test of multiple big block cylinder heads and intakes. This time around, Prestige wasn't content to simply complete a build with a Borla intake and ship it out, but instead wanted to do a little testing again, too.

For this test, Senior, Prestige's lead engine builder, had two pairs of practically identical AFR cylinder heads. Both heads are from AFR's Renegade line of aluminum heads for Windsor Fords. They feature 58 cc combustion chambers, CNC ported intake and exhaust runners, a competition five-angle valve job, and a valve spring upgrade for running high rpm with hydraulic lifters. The only difference is one set of heads has 205 cc intake runners (AFR part number 1450), while the second set has larger 220 cc runners (#1451).

On the engine dyno with the AFR 205 cc heads in place and Holley's Dominator engine management system running the injectors and timing, the engine settled in quickly and made good power. For comparison's sake, Prestige often builds this 427-cubic inch Windsor combo with an Edelbrock Victor Jr single-plane intake manifold and a 750 cfm Quick Fuel four-barrel carb, and it reliably produces 575 horsepower and 525 lb/ft of torque. Interestingly, by swapping out the single-plane intake and carb for the stack fuel-injection system with no other modifications, the peak horsepower jumped up by 21 to 596 at 6,300 rpm. The torque also improved 7 lb/ft, but what's interesting there is what velocity stacks will do to a V8's torque curve. Namely, it moves it way up the rpm range. On a smaller engine that may not always be desirable, but the 427 Ford with its 4 inches of stroke makes mountains of torque, so have it all come on at 3,000 rpm may be too much. With the Borla induction the Ford produces 435 lb/ft of torque at 2,500 rpm and just keeps climbing all the way to 533 at 5,500 rpm. In any car, an engine that just keeps pulling hard all the way past five grand is going to be a ton of fun.

After that, we pulled the intake and heads in order to swap them out for AFR's 220 cc intake Renegades. Surprisingly, even though a big-inch motor almost always like the larger runners, we didn't see much difference this time around. The needle for peak power barely moved—it topped out at 597.8 at 6,200 rpm—and the torque only improved by 6.

We suspected that the bottleneck on the additional power was coming from the Borla intake. It makes great power, but Borla obviously designed it to work best on a 350 cubic-inch engine. Our Windsor has an extra 77 cubes trying to ingest tons of air and fuel, which could be too much for it. So, being inveterate horsepower junkies looking for another fix, the staff at Prestige decided to pull the intake again and take a grinder to it to see if they can improve the flow even more. And that meant yet a third dyno test.

It turns out that AFR created most of the extra area in the 220cc runners by raising the roof. Borla's intake matched up with the runners on the 205cc heads almost perfectly, but all the extra area in the 220cc heads was wasted behind metal on the intake manifold. To cure this, Prestige welded extra aluminum to the top of the manifold near where it meets the cylinder heads and then reground the runners to perfectly match the larger heads.

After that, the engine was reassembled and put back on the dyno for a third time. And boy, was it worth it. The big-inch Ford was definitely hurting for air and the port work proved it. Peak horsepower jumped by 27, all the way to 624.3, while torque improved by at least 10 all the way across the board with peak torque improving by 20. And by the way, that's all on pump gas.

So what did we learn? The easy lesson is when it comes to making pure power, individual stack induction is tough to beat. In particular, the Borla system is well engineered with lots of quality touches and works well. If you have a Ford with 350 to 400 cubic inches, in stock form the Borla induction is going to be about perfect. If you are running a big-inch motor like ours or a pure performance, high-rpm screamer it is still going to work great, but with just a little port-matching work you can really unlock some horsepower.

See all 25 photos

See all 25 photos The foundation for this build is one of Dart's SHP Windsor blocks. Prestige prefers the Dart blocks because they offer good value, hold up to big power and can handle lots of stroke without modification.

See all 25 photos Stroke makes torque, and Prestige loves to build engines that make big torque. So an Eagle crank with 4.00 inches of stroke was ordered up for the build. It will ride on a set of King XP main bearings.

See all 25 photos The connecting rods are 6.250 long with a Chevy-size 2.100-inch main journal. They will be connected to a set of Mahle pistons to fill the 4.125-inch bores in the block.

See all 25 photos Dart's SHP design comes with a lot of great features, including steel main caps to help hold up to tons of horsepower. The inner bolts are torqued to 95 lb-ft with motor oil as a lubricant, while the outers were tightened to 65 lb-ft.

See all 25 photos The camshaft is a hydraulic roller. Prestige worked with Comp Cams to work out the custom grind with 253/259 degrees of duration at 0.050-inch lift with a 110-degree lobe separation angle. Using 1.6:1 ratio rockers, net valve lift will be 0.638-inch for both the intakes and exhaust.

See all 25 photos Engines with lots of stroke like deep oil pans to help move the oil away from the crank to mitigate windage, so we used a deep sump pan from Canton with large kick outs to increase the overall volume.

See all 25 photos Here's another view of the pan showing the kick outs. What you can't see is the Melling standard volume oil pump that will be used to provide lubrication throughout the engine.

See all 25 photos We'll be testing two sets of AFR Renegade heads for Ford Windsor engines. Both feature fully CNC'd ports and chambers. The chambers for both are 58cc's along with 2.100 intake and 1.570-inch exhaust valves. The only difference will be the first set has 205cc intake runners while the second, larger set has 220cc runners.

See all 25 photos Both heads will also use AFR's upgraded valve springs for hydraulic valvetrains.

See all 25 photos Scorpion's Endurance Series aluminum roller rockers maintain the Ford's stock 1.6:1 rocker ratio.

See all 25 photos This is the underside of Borla's stack induction system. Intakes with individual velocity stacks or throttle bodies require some type of common plenum to help the engine run smoothly. Many use a network of balance tubes connected to each runner, but Borla's intake utilizes an integrated plenum to balance the engine's pulses while remaining hidden on the underside of the intake. Here, with the cover off you can see the holes drilled from each runner into the common plenum.

See all 25 photos With the lower cover bolted up, the plenum is sealed and everything remains hidden.

See all 25 photos Finally, the Borla intake setup is ready to be dropped into place. Each of the velocity stacks are CNC machined and come equipped with 47 lb/hr injectors.

See all 25 photos This is a look at the back of the intake. In the center just below the dual fuel rails is the integrated, adjustable fuel pressure regulator. Just to the left of that is the throttle position sensor.

See all 25 photos Looking between the velocity stacks, you can see the trick billet throttle linkage system designed to take the guesswork out of getting all eight butterflies to open equally. Just in front of that is the plug to monitor manifold air temp.

See all 25 photos Spark routing is handled by an MSD Pro Billet distributor. Before we dropped into place, we switched to a steel drive gear to help it mate with the roller cam better. We also switched the advance springs and bushings (now using a blue and silver advance spring) to shorten and speed up the advance curve.

See all 25 photos Fuel mapping and all engine management chores are handled by Holley's Dominator engine management system.

See all 25 photos On the dyno, the Dominator ECM quickly got the big 427 under control and developed a customized fuel map to fit the needs of the stroker Ford. After a few manual tweaks by the Prestige staff, the engine was making 596 hp and 533 lb-ft of torque with the smaller AFR cylinder head with 205cc intake runners. That's pretty impressive considering the same engine package typically makes 575/525 with a single plane intake and 750 cfm carb. As soon as the engine cooled, the staff at Prestige began the cylinder head swap to see how the engine liked larger 220cc runners.

See all 25 photos On the dyno, the Dominator ECM quickly got the big 427 under control and developed a customized fuel map to fit the needs of the stroker Ford. After a few manual tweaks by the Prestige staff, the engine was making 596 hp and 533 lb-ft of torque with the smaller AFR cylinder head with 205cc intake runners. That's pretty impressive considering the same engine package typically makes 575/525 with a single plane intake and 750 cfm carb. As soon as the engine cooled, the staff at Prestige began the cylinder head swap to see how the engine liked larger 220cc runners.

See all 25 photos In order to keep everything on this test as even as possible, the valve springs were swapped over from the old heads to the new.

See all 25 photos After not seeing the horsepower improve like they expected with the larger 220cc heads, the guys at Prestige Motorsports decided to port the Borla intake. After "printing" the manifold (bolting the manifold back to the engine and heads with machinist's dye to mark the areas where they touch), you can see the area in red on the manifold that needs to be ground away to match the 220cc ports on the AFR Renegade cylinder heads.

See all 25 photos Because so much area had to be cut away from the roof of the runners, Prestige had to weld some more material to the ends of the manifold to create additional area before machining it back to form and grinding the new runners.

See all 25 photos Looking at the dyno graph, the second dyno test with the larger cylinder heads was a bit of a disappointment. As you can see, both the horsepower and torque curves for both the 205 and 220cc heads are nearly identical. Big-inch strokers almost always like larger intake ports, so the staff at Prestige decided there must be a port-match problem between the intake and cylinder heads. So after a couple days spent porting the Borla intake manifold everything went back on the dyno for a third run. As you can see by the blue (torque) and green (horsepower) graphs for our third dyno test, a little port work yielded big improvements in horsepower.