Chevy 505ci Big Block Cylinder Heads - Freedom Flow

We dig it when we get to be first in line to try out the latest go-fast goody from the aftermarket, so we jumped at the chance to lay our hands on a prototype set of Patriot Performance's new Freedom Series aluminum big-block Chevy cylinder heads and put them to the test. Our methodology was pretty cut and dried: We took a proven bottom end, specifically a 505ci stroker short-block from JMS Racing engines, equipped it with an aggressive Isky solid roller cam spec'd to complement the heads, topped it all off with the new lungs, then ran it on the dyno to see what was what. How'd it all work? Let's just say we were far from disappointed.

Patriot decided to aim its new big-block castings squarely at the street/strip enthusiast. Accordingly, the heads use 320cc rectangular intake ports. "It's small enough to work on the street," says Patriot's Gunnar Bowlin. "It also has a lot of flow," he continues. And that, of course, lends itself toward higher-rpm power. We know you've already flipped the page and checked out the dyno charts for our test, so we won't play coy here. Although Bowlin says these heads aren't for torque applications-e.g., low-rpm cruiser setups-our Isky-cammed test mule was anything but short on grunt. We will admit that it only makes 5 inches of vacuum at idle; with this cam, plan on a booster if you want power brakes. If you like raspy and loping, the idle quality is great. Most importantly for our purposes, however, is the fact that this thing is already making northward of 600 lb-ft at 3,500 rpm, and it maintains this type of grunt through most of the powerband, peaking at 5,100 rpm-which we'd say covers the "street" side of the equation.

Of course, that still leaves the "strip" side of the coin. According to Patriot, the new Freedom Series heads flow 369 cfm at 0.700 inch lift, and we chose our camshaft to take advantage of these heads' flow characteristics (see the sidebar) while also creating the aforementioned long, flat torque band. As it turned out, we had enough flow to support 674 hp at 6,300 rpm; in fact, our mule stayed well over the 600 mark from 5,100 rpm all the way to the end of the pull. Assuming you can make the thing hook up, it's the kind of power that'll put a 3,500-pound car well into the 10s, theoretically speaking. We could go on and on about it, but when you get right down to it, our JMS Racing 505, breathing through Patriot's new heads, made the big numbers we like to see.

On the other hand, nobody likes to see big numbers when it comes time to buy a set of big-block heads. In their baseline configuration (assembled with valvesprings that will accommodate up to 0.600 inch valve lift), the Freedom Series big-block heads go for a paltry $1,295 a pair. Ours came with springs that can handle up to 0.700 inch lift; even with the titanium retainers included in this package, the bill only comes in at $1,495. A setup with 0.800-inch springs also adds Ferrea valves to the mix and goes for $200 more. "We were looking to produce a great-performing head with exceptional quality at a terrific price," says Bowlin. In our book, all three of those goals have been met.

And although this story was primarily created to test the power potential of Patriot's big-block heads when matched with an appropriate cam, we couldn't help but include the cost for the entire engine build while we were at it. Even with the cost of the Isky solid roller cam and Red Zone lifters, the total tab on this 674-horse creation from JMS Racing Engines was a mere $8,730. Consider it a bonus, and read on to get the full story on these new heavy-breathing heads.

Quick Notes
What We Did
Try out Patriot Performance's new heads on a solid roller-cam 505ci big-block

Bottom Line
These heads work and they won't empty your wallet.

Cost (approx)
$1,495

Picking The 'Stick
When it came time to pick a camshaft for this project, we decided to practice what we preach and seek professional help. In short, we told our man at Isky Racing Cams, Nolan Jamora, that we were looking for a street/strip solid roller cam that would give us a big horsepower number but also provide a broad torque band that would lend itself to drivability. The flow bench figures we provided allowed Jamora to tailor the cam to take advantage of the Patriot heads' qualities while also meeting our powerband goals. He recommended a 108-degree-LSA center as the best compromise between power and drivability. "Less would get us more power," Jamora observed, "but it'd be in a quicker range." After reviewing the flow numbers, he came up with lift figures of 0.640 inch intake and 0.650 inch exhaust. "These heads flow well at the top end, so we want to take advantage of that," Jamora explained. The duration figures, 262 degrees on the intake and 272 on the exhaust, were chosen to keep the powerband in a usable rpm range. It'd be an understatement to say we're thrilled with the results. "The cam's not really that big," Jamora summed up. "We got a flat torque band and a good horsepower number, and it's all in a real-world, usable rpm range. The power comes on and stays on for a while." For our part, we'll just say the time taken to match our cam to these new heads was time well spent.