Get high-dollar glory
for the iron head price with...
aluminum heads from Patriot
Anytime you can find a brand-new set of small-block Chevy aluminum heads complete with val
`If you want the glamorous look and easy porting that come with a set of top-of-the-line aluminum cylinder heads without the big price, the new line of alloy small-block Chevy heads from Patriot Performance will do the trick. Patriot sells these small-block Chevy assembled heads for $795 a pair ready to bolt on, so they'll give you the street cred you crave and a little extra horsepower to boot.
There are several ways to evaluate cylinder heads besides just price. Frankly, just because a set of heads is affordable doesn't mean they're a good buy. We decided to both flow-test them and then wring 'em out on an engine. The test consisted of using both a SuperFlow 600 flow bench and then the engine dyno. We started by bolting on a set of iron Vortec heads and comparing them to the new Patriots using a flat-top piston, 355ci small-block. In our opinion, the Vortecs are now the new standard by which all mild small-block Chevy heads should be compared. So let the test begin!
Rebuilt Iron vs. New Aluminum
Let's suppose you're an entry-level car crafter with a limited budget about to rebuild a small-block Chevy. We'll assume that, as with most worn-out iron heads, the castings will need new guides, valves, springs, retainers, keepers, machined for positive seals, screw-in studs and guideplates, and a performance valve job. By the time all this work is finished, you will have a minimum of $500 to $800 invested in a set of ancient iron heads that don't flow all that well. Or you could invest in a set of all-new Patriot aluminum heads that are lighter, easier to repair if they have a problem, and still offer a performance advantage over earlier stock iron heads. One disadvantage may be that these Patriot heads are only available with 64cc chambers, which can pump the static compression up slightly compared to a set of 76cc heads. This smaller chamber is advantageous if used on a smaller-displacement engine like a 327.
The Patriot 188cc heads are available only with 64cc chambers (we measured 66 cc), but do offer the advantage of a late-model-style chamber configuration. In previous dyno tests, we've concluded that there is no real advantage in terms of iron versus aluminum when it comes to power.
The Patriot 188cc heads are available only with 64cc chambers (we measured 66cc), but do o
The 188cc Patriot heads are hand-blended from the seat insert to the bowl area. Nonblende
The 188cc Patriot heads are hand-blended from the seat insert to the bowl area. Nonblended heads are also available if you wish to do the work yourself. It appears there may be an advantage to doing this if you have some experience with a grinder.
We had Slover's Porting Service machine our Vortec iron heads for screw-in studs just to m
We had Slover's Porting Service machine our Vortec iron heads for screw-in studs just to make them more reliable. Scoggin-Dickey had already modified the heads to accommodate more valve lift.
The Patriot Freedom Series 188cc heads come with 2.02/1.60-inch stainless steel valves, flat-tappet hydraulic valvesprings, and screw-in studs and guideplates. The castings look especially nice considering their price.
The Patriot Freedom Series 199cc heads come with 2.02/1.60-inch stainless steel valves, fl
The Patrio heads come complete with 1.250-inch valvesprings, 3/8-inch screw-in studs, and
The Patriot heads come complete with 1.250-inch valvesprings, 38-inch screw-in studs, and raised guideplates and are drilled for both perimeter and centerbolt valve covers. As you can see, the castings are excellent.
Flow Bench Testing
Patriot's advertising concentrates on the exceptional 260-plus-cfm potential of this head at 0.600-inch valve lift, but that's really only half the story. Our flow measurements confirmed this strong number, but unfortunately most street engines that would use this head would rarely combine a camshaft with a 0.600-inch or taller valve lift curve. Using the Crane catalog for reference, we'd have to go all the way up to a 256-degree at 0.050 mechanical roller cam to get the lift up over 0.600 inch. That's not a practical camshaft--it's just too much duration for a set of 188cc intake port heads.
The better place to compare intake flow numbers for most street cylinder heads is in the midlift flow area, with an emphasis on the 0.300- and 0.400-inch valve lift flow numbers. Looking at these numbers, it appears the Vortec intake port is a bit stronger. At 0.300 inch of intake valve lift, the Vortec has a 21-cfm advantage, which is 12 percent. Taking this even further, we also have to look at the exhaust side. Here, the Patriot heads have a slight advantage again at 0.400- and 0.500-inch valve lifts. This first-blush flow bench test does not paint the Patriots in glorious terms, but the bottom line is that we don't drive flow benches. So the next step is to bolt these heads on and see what kind of power they can make.
All our cylinder head testing was performed on Jim Grubbs' SuperFlow 600 bench at 28 inches of water using a 4.030-inch bore diameter to duplicate the bore diameter used on our test 355ci engine.
All our cylinder head testing was performed on Jim Grubbs' SuperFlow 600 bench at 28 inche
The exhaust ports on the Patriot 188cc heads are larger than the Vortecs and probably cont
The exhaust ports on the Patriot 188cc heads are larger than the Vortecs and probably contributed to the peak horsepower increase these heads generated compared to the iron heads. For example, at 0.500-inch valve lift, the Patriot exhaust port is up a solid 15 cfm.
Since there are far more 355ci small-block Chevys out in the performance world than blurry Internet copies of the Paris Hilton video (or so we've been told), we figured this would be the perfect engine to use as our mule motor. This is the same small-block we used in our E85 supercharger test (E85 Pump Gas, Feb. '07) where we made 601 hp on 85 percent fresh-squeezed corn juice. The short- block consists of a stock-stroke crank along with 5.7-inch rods and a set of Ross flat-top forged pistons. The cam is a Crane PowerMax 288 flat tappet hydraulic using 1.6:1 rockers to pump the lift up to almost a half-inch on the intake side. We figured this was a very streetable camshaft that is typical of what the fashionable mild street small-block Chevys are wearing these days.
As for the induction side of things, this gave us a chance to use a pair of Weiand's new Stealth Air Strike dual-plane intake manifolds. The Vortec heads require a special intake bolt pattern, but otherwise the two manifolds are the same and are topped with a classic Holley 750-cfm mechanical secondary carburetor. For exhaust, we went with a set of Hedman 134-inch street-type headers muffled with a pair of 212-inch Flowmaster mufflers.
With the Vortec heads secured to the 355ci short-block, the power numbers for the production iron heads fell in almost exactly where we expected. These heads, with a mild hydraulic cam, will make around 380 hp on a 355ci small-block, and this motor was no exception. Even with a little more compression at 10.2:1 on 91-octane pump gas, this version came in at 410 lb-ft for torque and 385 for horsepower. True to form, the iron lungs made excellent torque, generating over 400 lb-ft of torque for a 1,200-rpm power spread. We set the total ignition timing at 36 degrees.
Once we were satisfied that the Vortec heads had given their best, we called for the Patriots. We hadn't noticed it before, but the Patriots are actually machined for both the standard and the Vortec-style intake manifold bolt pattern. We really didn't need the standard-style Weiand Air Strike manifold, but we used it mainly because we had it. We retained the same Holley 750-cfm carb, and no other pieces were changed other than to go to a set of Crane nonguided Gold Race 1.6:1 roller rockers to maintain the same valve lift dimensions for both heads.
After a quick timing exercise, the Patriot heads were happiest with the same 36 degrees of total ignition timing as the Vortec heads. On the fuel side, the Holley was a little rich in the midrange but ended up with an excellent 12.8:1 air-fuel ratio at peak power, which is exactly the same curve it delivered with the Vortec heads. Because this was a cylinder head test, we didn't want to start modifying the carburetor to try and improve the fuel curve, but it does appear that we could probably pick up some torque with either head by leaning out the midrange fuel curve.
As you can see from the dyno chart, the Vortec heads took the peak torque crown while the Patriots won the horsepower battle. But look a little deeper into the overall torque curve and you'll see that the Patriots gave up torque compared to the Vortec heads throughout the power curve until above 5,100, where they made more horsepower. This looks bad, but when you compare the average torque and horsepower numbers at the bottom of the dyno chart, note that the Patriots gave up less than 5 lb-ft of torque and barely 3 hp on average. Add in the aluminum weight factor, and our consensus is that it would be difficult to see a significant advantage if these two went head-to-head in a car.
We conclude that if we could improve the Patriots' midlift flow with a different valve job and/or more conservative throat-diameter percentage, these heads have the potential to really help the torque curve while also adding to the top-end power as well. But even out of the box, the Patriots offer decent performance for the money and would be a good investment for any car crafter looking for an affordable, entry-level aluminum small-block Chevy cylinder head.
we used Crane Gold Race 1.6:1 roller rockers to coax more lift out of the PowerMax 288 cam
We used Crane Gold Race 1.6:1 roller rockers to coax more lift out of the PowerMax 288 cam. Vortec heads require narrow-body, guided rockers to clear the centerbolt valve covers.
To baseline the Vortec heads, we also included a Weiand Stealth Air Strike dual-plane intake manifold along with a Holley 750-cfm, mechanical secondary carburetor.
We topped off the Patriot aluminum heads with a pair of nice painted valve covers from Proform that also include separators to keep oil off the top of the engine.
To baseline the Vortec heads, we also included a Weiand Stealth Air Strike duel-plane inta
We topped off the Patriot aluminum heads with a pair of nice painted valve covers from pro
We bolted on the Vortec heads, Weiand Air Strike intake, and Holley 750 carb with Fel-Pro
We bolted on the Vortec heads, Weiand Air Strike intake, and Holley 750 carb with Fel-Pro gaskets, and commenced to beating on our trusty small-block to generate some hard numbers. The Vortec couldn't quite reach the 400hp mark, with a respectable 385 hp at 5,700 rpm. Torque came in strong at a solid 410 lb-ft at 3,900 rpm. This combination made 311 lb-ft of torque at a tractorlike 2,100 rpm.
Test 1 ran the Scoggin-Dickey-modified Vortec heads along with 1.6:1 Crane roller rockers with a 10.2:1 static compression ratio in our 355ci short-block assembly. We also bolted on a Holley Stealth Air Strike dual-plane intake manifold with the Holley 750cfm carb and a set of 134-inch headers.
Test 2 is the same engine combination except with the Patriot aluminum cylinder heads. We used an almost identical Holley Stealth Air Strike manifold, this one designed with the standard small-block intake bolt pattern. Since the Patriot chambers measured 66 cc, the static compression was down from 10.2 to 10.0:1, which may account for a tiny power loss just from compression. END
Automotive Racing Products; Oxnard, CA; 800/826-3045; arp-bolts.com
Crane Cams; Daytona Beach, FL; 386/258-6174; cranecams.com
Federal-Mogul; Detroit, MI; 810/354-7700; federal-mogul.com
GM Performance Parts; Warren, MI; 800/577-6888; gmperformanceparts.com
Holley Performance Products; Bowling Green, KY; 270/781-9741; holley.com
Patriot Performance; Rainbow City, AL; 888/462-8276; patriot-performance.com
Royal Purple; Porter, TX; 888/382-6300; royalpurple.com
Scoggin-Dickey Parts Center; Lubbock, TX; 806/798-4013; sdpc2000.com
Slover's Porting Service; Sun Valley, CA; 818/768-0155