Chevy 505ci Big Block Cylinder Heads - Freedom Flow
Patriot Performance's New Freedom Series BBC Heads Deliver On The Dyno
From the January, 2008 issue of Chevy High Performance
By John Nelson
Photography by John Nelson
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.
What We DidTry out Patriot Performance's new heads on a solid roller-cam 505ci big-block
These heads work and they won't empty your wallet.
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.
CAMSHAFT SPECS ...
|CAMSHAFT SPECS |
|Manufacturer ||Isky Racing Cams |
|Part Number ||RR-645 |
|Type ||solid roller |
|Valve Lift ||0.640/0.650 inch, |
| ||intake/exhaust |
| ||(1.75:1 rockers) |
|Duration ||264/272 degrees @ |
| ||0.050, intake/exhaust |
|Lash (hot) ||0.028/0.028 inch, |
| ||intake/exhaust |
|Lobe Center ||108 degrees |
1. Carburetion duties are...
1. Carburetion duties are handled by a Mighty Demon 850 mixer squirting through an 85/93 jet combo; the intake is a tried-and-true Edelbrock Victor Jr. 454-R.
2. Patriot Performance's Freedom Series aluminum big-block heads feature 320cc rectangular intake ports along with 2.25/ 1.88-inch valves. At $1,495 as delivered, they're a steal.3. True to its street/strip mission, this cam/ heads combo yielded 674 hp at 6,300 rpm, but also maintained an exceptionally broad torque band that peaked at 624 lb-ft.
4. Isky Red Zone lifters, one-piece pushrods, and 1.75:1 roller rockers complement the stout solid roller cam. 5. Hooker 2 1/8-inch Super Comp headers deal with the burnt junk.
6. The JMS Racing Engines' short-block runs a 4.350x4.250-inch bore and stroke combo to create 505ci. The two-bolt main block uses ARP studs for strength and comes with forged rods and KB Performance pistons. Compression checks in at 10.5:1.
Whenever JMS Racing Engines...
Whenever JMS Racing Engines installs a camshaft, it breaks out the degree wheel to make sure the new 'stick is correctly phased, and this time was no different. We've covered this job in more detail in the past, so here we'll just point out that for proper installation we used the "square" mark on our crankshaft gear rather than the straight-up position.
When running a roller cam...
When running a roller cam on a block that lacks provision for a thrust plate, a button must be used to limit the cam's lateral movement. If the cam moves too much, ignition timing can be thrown off, hurting performance. The movement is checked by carefully pushing the cam forward in the block against the timing cover. Want a quick way to do it? Install the cover without a gasket, then set the button so it's against the cover. With the gasket in place, the cam will have the proper 0.003-0.005 inch of end play.
Once the cam thrust is set,...
Once the cam thrust is set, the button-in this case one of Isky's slick needle-bearing pieces-is held in place with a lock plate.
The combustion chambers measure...
The combustion chambers measure 119 cc; Patriot's Race Series valves come undercut and swirl-polished. The chambers in these prototype heads were hand-worked to clear a domed piston. The modification will be incorporated into the production castings.
Removing a set of valves reveals...
Removing a set of valves reveals a nice five-angle valve job ground to Patriot's proprietary specs.
The valve-seat contours are...
The valve-seat contours are hand-blended into the runners on both the intake and exhaust sides. Patriot Performance will CNC-bowl-blend and gasket-match your chosen head for and extra $200; full CNC porting costs $450 extra.
Rectangular intake ports measure...
Rectangular intake ports measure 320 cc, small enough to help create low-rpm torque but large enough to support high-rpm power.
The lifter cup height in Isky's...
The lifter cup height in Isky's Red Zone roller lifters is identical to that in its solid lifters, so if you use them on a stock head, stock-length pushrods will work. Patriot Performance, however, uses "plus length" valves (0.250 inch on the intake, 0.100 inch on the exhaust) to allow for the installed spring heights needed with today's high-lift camshafts. JMS used a measuring pushrod to determine the correct pushrod length, which turned out to be 0.100 inch longer than stock.
We topped this combo off with...
We topped this combo off with a Victor Jr. intake, a Mighty Demon 850 carb and fuel fittings, and a Mallory 32 Series Comp S/S distributor that was ready to run.
To make sure we got every...
To make sure we got every bit of lift and duration out of our cam, we installed a set of 1.75:1 roller rocker arms-this is the ratio Isky uses to calculate its big-block cam specs. The cam card called for 0.028-inch hot lash on both the intake and exhaust valves. Jeff Johnson set this clearance, then went back and reset it once the engine was hot.
Once the valves were set,...
Once the valves were set, it didn't really take long to dial this combo in. The Mighty Demon was spot-on out of the box, and the engine liked 38 degrees of total timing. We liked the big power numbers-and gobs of torque-this Patriot-headed, Isky-cammed setup made.
We decided to run Isky's Red...
We decided to run Isky's Red Zone solid roller lifters. The oil holes make sure the needle-bearing rollers stay lubed under the low-oil-pressure, high-heat conditions they'll see on the street. If these lifters do wear out, don't worry-they're fully rebuildable.
|505CI BIG-BLOCK DYNO DETAILS |
|Headers ||2 1/8 Hooker Super |
| ||Comp upswept |
|Fuel ||91-octane |
|Carburetor ||Mighty Demon 850 |
|Jets ||85/93 |
|Advance ||38 degrees |
|RPM ||LB-FT ||HP |
|3,500 ||606 ||404 |
|3,600 ||605 ||415 |
|3,700 ||600 ||423 |
|3,800 ||594 ||430 |
|3,900 ||590 ||438 |
|4,000 ||590 ||449 |
|4,100 ||593 ||463 |
|4,200 ||594 ||475 |
|4,300 ||590 ||483 |
|4,400 ||595 ||499 |
|4,500 ||603 ||517 |
|4,600 ||609 ||533 |
|4,700 ||612 ||547 |
|4,800 ||614 ||561 |
|4,900 ||620 ||578 |
|5,000 ||623 ||593 |
|5,100 ||624 ||606 |
|5,200 ||620 ||614 |
|5,300 ||616 ||621 |
|5,400 ||613 ||631 |
|5,500 ||607 ||636 |
|5,600 ||601 ||641 |
|5,700 ||596 ||646 |
|5,800 ||594 ||656 |
|5,900 ||590 ||663 |
|6,000 ||588 ||671 |
|6,100 ||579 ||673 |
|6,200 ||569 ||672 |
|6,300 ||562 ||674 |
|6,400 ||553 ||674 |
|6,500 ||541 ||669 |
|AVG ||596 ||566 |
|GO WITH THE FLOW |
|LIFT ||INTAKE ||EXHAUST |
|(inch) ||(cfm) ||(cfm) |
|0.100 ||86.6 ||63.6 |
|0.200 ||177.5 ||148.0 |
|0.300 ||252.3 ||192.1 |
|0.400 ||295.0 ||231.7 |
|0.500 ||329.6 ||256.8 |
|0.600 ||359.1 ||268.9 |
|0.700 ||368.2 ||275.1 |
|SOLID ROLLER 505 PARTS LIST |
|ARP ||135-9801 ||Accessory bolt kit ||80 |
| ||135-2501 ||Balancer bolt ||21 |
| ||135-3603 ||Head bolts ||85 |
|Barry Grant ||5423010GC ||Mighty Demon 850 carb ||550 |
|Edelbrock ||2902 ||Victor Jr. 454-R ||230 |
|Federal-Mogul/Felpro ||1017-1 ||Head gaskets ||80 |
| ||1275 ||Intake gaskets ||16 |
| ||1606 ||Valve cover gaskets ||15 |
| ||224-4153 ||Oil pump ||39 |
|Isky Racing Cams ||9.350/8.600 ||Pushrods, intake/exhaust ||120 |
| ||372-96-RH ||Red Zone roller lifters ||585 |
| ||204-96 ||1.75:1 roller rockers ||425 |
|JMS Racing Engines ||496/505 short-block || ||$3,450 |
| ||Includes ARP main-bearing cap studs; Federal-Mogul bottom gaskets, cam bearings, rod bearings, and timing set; Isky solid roller camshaft; nodular iron crankshaft with 4.250-inch stroke; forged 6.385-inch rods; KB Performance 0.100-over Premium forged pistons and rings. |
| || ||Complete short-block Labor ||600 |
| || ||Flexplate ||35 |
|Mallory ||3248201 ||32 Series Comp S/S distributor ||185 |
| ||938 ||Pro Sidewinder Plug wires ||70 |
|Moroso ||21047 ||Eliminator oil pan ||440 |
| ||24440 ||Pick-up ||39 |
|Patriot Performance ||2226 ||Freedom Series BBC heads ||1,495 |
| || ||w/7.00-inch springs || |
|Summit ||SUM-164800 ||Adjustable timing pointer ||25 |
| ||SUM-G3312 ||Chrome valve covers ||30 |
| ||SUM-162454 ||OEM harmonic balancer ||84 |
| ||SUM-G3201 ||Chrome timing cover ||11 |
| ||SUM-G3405 ||Valve cover breathers (2) ||20 |
| || ||Total ||$8,730 |