Like most ideas, this one started out with a simple statement: "Hey, let's test a few LS heads." From that innocent phrase came what would become the granddaddy of all LS cylinder head tests. Sure, we could have tossed them all on the airflow bench, provided some fancy flow numbers, and called it a day, but did we stop there? Not hardly. We here at HOT ROD are all about taking things to the next level, so we decided to add port-volume measurements and dyno testing to our already very long LS to-do list.
This is part one of a series that will thoroughly test all the available LS heads we can get our hands on. We're starting here with the LS1/LS2/LS6 cathedral-port versions. We plan on following up this adventure by testing both LS3 and LS7 heads, but for now, let's get back to the killer cathedrals.
Knowing we will be running a plethora of performance heads that exceed 300 cfm (enough flow to easily support more than 600 hp), we needed something more than your run-of-the-mill LS1 crate motor. To that end, we assembled a 408 stroker that offers more cubes, more cam, and more compression than a stock LS1, LS2, or even LS6. The 408 has a 4.00-inch forged-steel crank, matching connecting rods, and forged, dish-top pistons from Probe Racing. Wanting to tax the flow capacity of the cylinder heads, we installed an aggressive hydraulic roller cam from Comp Cams. The LSR cathedral-port profile offers 0.624 lift (with 1.7:1 rocker ratio), 239/247 duration (at 0.050), and a 114-degree lobe-separation angle. The lift was slightly higher with the 1.72 roller rockers run on most of the heads.
Each of the cylinder heads was run using the same set of 17/8-inch headers from American Racing and tuned using the Fast XFI/XIM management system. The air/fuel was dialed in to 13.0:1 at peak power rpm, and every head ran best with 30 degrees of total timing. Sweeps were made with more and less timing (4 degrees in each direction), but all we managed to do was lose power. Naturally, variables such as air and water temperatures were also kept consistent between runs. Each set of heads was run from 3,000 rpm to 6,700 rpm (some slightly higher if the power curve continued to climb). We gathered not only the peak power numbers but also the average horsepower and torque production from 3,000 to 6,500 rpm and torque production measured at 4,000 rpm (to give an indication of the torque lower in the rev range). In addition to the dyno results, every head was run on the flow bench and tested for combustion chamber and intake port volume. Per our instructions, the manufacturers supplied their heads with 64cc chambers (our measurement only verified that we had no high-compression ringers) and sufficient spring pressure to allow for the 0.624-lift cam and 7,000-rpm potential.
While every LS owner will naturally be looking for us to declare a winner, the reality is a bit more complex. First and foremost, we discovered that the manufacturers had sufficient confidence in their products that they were willing to subject them to such an ordeal. In any contest, there will be perceived winners and losers, but the results of any dyno tests are application specific. Our combination of displacement, cam timing, and intake may have favored one or more cylinder head configuration over another. Tested on a different application, the results would certainly be different. On many of the heads, the results varied by only a couple of horsepower. In the grand scheme, that's insignificant.
The dyno graphs provided with each head test compare them with the stock head curve. Let the Internet bickering begin.
Test 1
Stock LS1
Retail price: N/A
Intake valve size: 2.0
Exhaust valve size: 1.55
Intake port volume: 205 cc
Exhaust port volume: 70 cc
Chamber volume: 68 cc
Peak power: 549.6 hp at 6,200 rpm
Peak torque: 517.2 lb-ft at 4,800 rpm
Average horsepower (3,000-6,500): 442.1 hp
Average torque (3,000-6,500): 488.7 lb-ft
Torque at 4,000 rpm: 499.8 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 32 24 0.100 64 55 0.200 137 106 0.300 190 141 0.400 216 179 0.500 228 193 0.600 238 203 0.650 242 204 0.700 244 206
The stock LS1 heads (241 castings) were run on the 408 to establish a baseline. They have 68cc combustion chambers, so the compression was slightly lower than the test heads, but much of the power difference can be attributed to the fact that the stock heads offered peak flow numbers of 244 cfm. Though down in flow considerably compared with the aftermarket heads, they represented a significant step up the performance ladder compared with traditional small-block castings (the stock LS1 heads flow 40 cfm more than even the legendary fuelie heads of the late '60s). The 241 castings feature 205cc intake ports, 70cc exhaust ports, and a 2.0/1.55 valve combination. The hot factory heads would be the LS6 (243 castings), but even the stock LS1 heads can be made to flow well with proper porting.
Test 2
AFR 245
Retail price: $2,699
Intake valve size: 2.160
Exhaust valve size: 1.6
Intake port volume: 244 cc
Exhaust port volume: 87 cc
Chamber volume: 64 cc
Peak power: 622.1 hp at 6,400 rpm
Peak torque: 558.3 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 474.9 hp
Average torque (3,000-6,500): 519.7 lb-ft
Torque at 4,000 rpm: 511.7 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 27 0.100 68 55 0.200 152 117 0.300 225 176 0.400 278 214 0.500 318 230 0.600 343 241 0.650 352 240 0.700 341 242
The new Air Flow Research (AFR) 245 heads offer impressive flow numbers, registering 352 cfm at 0.650 lift. Second in size only to the LS3 Mast heads, the AFR 245s featured massive 2.160-inch intake valves combined with the apparently industry standard 1.60 exhaust valve. In truth, the 245 heads were probably better suited to a bigger-bore motor and possibly an even wilder engine combination, but they nonetheless performed well on our milder 408. The peak torque production of 558 lb-ft was equaled by TFS and Texas Speed and bettered only by the Mast LS3 heads.
Test 3
Dart Pro 1 CNC 250
Retail price: $2,796
Intake valve size: 2.08
Exhaust valve size: 1.60
Intake port volume: 249 cc
Exhaust port volume: 94 cc
Chamber volume: 64 cc
Peak power: 613.2 hp at 6,400 rpm
Peak torque: 554.6 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 473.9 hp
Average torque (3,000-6,500): 519.5 lb-ft
Torque at 4,000 rpm: 509.8 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 37 24 0.100 70 54 0.200 144 110 0.300 216 157 0.400 265 196 0.500 304 225 0.600 318 235 0.650 322 238 0.700 317 240
As it comes from Dart, the name Pro 1 is synonymous with power. Measuring 250 cc, the Pro 1 LS heads feature the largest port volumes of any of the cathedral-port heads (eclipsed only by the Mast rectangular-port LS3 heads). The Dart Pro 1 heads offered enough peak intake flow to easily support more than 600 hp with 2.08/1.60 valves. Despite a significant increase in port volume, the Dart head offers an additional 10 lb-ft over the stock head at 4,000 rpm. The critical element in power production is obviously not port volume but the airflow increase in relation to port volume. Interestingly, the AFR heads flowed more on the bench, yet the Dart units with larger ports and less flow made nearly equal power.
Test 4
LPE Edelbrock
Retail price: $2,995
Intake valve size: 2.10
Exhaust valve size: 1.60
Intake port volume: 234 cc
Exhaust port volume: 84 cc
Chamber volume: 64 cc
Peak power: 615.7 hp at 6,600 rpm
Peak torque: 553.7 lb-ft at 5,300 rpm
Average horsepower (3,000-6,500): 474.9 hp
Average torque (3,000-6,500): 520.9 lb-ft
Torque at 4,000 rpm: 516.7 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 32 24 0.100 63 53 0.200 129 110 0.300 191 160 0.400 245 196 0.500 284 213 0.600 318 222 0.650 321 225 0.700 305 227
When you think of LS performance, it is hard not to think of the name Lingenfelter. The late John Lingenfelter was not only a great guy, but he was also a serious and extremely capable racer and engine builder. That commitment to quality and performance has carried on, as the gang at Lingenfelter has some impressive offerings for the LS crowd. Though they feature a number of ported heads using factory castings, we chose a set of the company's Edelbrock heads. Starting with as-cast Edelbrock LS1 heads, LPE runs them through its own CNC program to significantly improve the flow and power potential. When completed, the LPE Edelbrock heads feature a 2.10/1.60 valve package, a 235/84cc intake/exhaust port volume, and 64cc combustion chambers. Down at 4,000 rpm, the LPE heads thumped out 516.7 lb-ft and also gained more than 65 hp over the stock LS1 heads.
Test 5
Mast Black Label LS3 (Small Bore)
Retail price: $2,998
Intake valve size: 2.165
Exhaust valve size: 1.60
Intake port volume: 257 cc
Exhaust port volume: 86 cc
Chamber volume: 64 cc
Peak power: 620.1 hp at 6,600 rpm
Peak torque: 563.3 lb-ft at 5,300 rpm
Average horsepower (3,000-6,500): 477.4 hp
Average torque (3,000-6,500): 523.4 lb-ft
Torque at 4,000 rpm: 514.3 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 24 0.100 70 52 0.200 142 110 0.300 215 143 0.400 274 205 0.500 313 225 0.600 342 239 0.650 352 247 0.700 335 250
We know this rectangular-port head really doesn't belong in this cathedral-port head test, but we included it for a number of reasons. One was the fact that (just like the cathedral-port heads) this small-bore rectangular-port LS3 head was designed specifically for a 4.030-bore application. As such, the Mast head is a market competitor for the cathedral-port heads, despite the LS3 intake and offset rocker arms required. The second reason is that we wanted to see just how the considerable change in port volume (compared with most of the cathedral-port heads) might affect the low-speed power production. The general consensus is that larger port volumes decrease cylinder filling at lower engine speeds. Were that the case, we'd expect the big ports on the Mast LS3 heads to lose power down low, but that was not the case, as despite intake port volumes of 257 cc and the largest 2.165-inch intake valves, the Mast heads offered the highest peak torque output of 563 lb-ft at 5,300 rpm. The oversized port volumes didn't hinder the average power numbers, either. As we went to press, Mast announced it is introducing a far bigger line of 14 different LS heads, including cathedral ports.
Test 6
ProComp Motorsport LS1
Retail price: $1,875
Intake valve size: 2.055
Exhaust valve size: 1.60
Intake port volume: 219 cc
Exhaust port volume: 79 cc
Chamber volume: 63 cc
Peak power: 629.1 hp at 6,600 rpm
Peak torque: 557.0 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 476.6 hp
Average torque (3,000-6,500): 521.3 lb-ft
Torque at 4,000 rpm: 509.9 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 25 0.100 72 57 0.200 148 113 0.300 203 155 0.400 261 195 0.500 301 213 0.600 321 219 0.650 321 223 0.700 306 224
This head test was full of surprises, which is why we go to all the trouble of dyno testing in the first place. Just as surprising as the fact that the big Mast head offered the most torque, the heads with the smallest port volume offered the highest peak power. The CNC-ported LS1 heads from ProComp Motorsport are brand-new. Recognizing that the company's previous head was not a serious player in the LS market, it went to great effort and expense to design a dedicated casting that could stand toe to toe with the best heads on the market-and do so with a substantial cost savings. Measuring just 219 cc, the intake ports featured 2.055 intake valves. The flow rates checked in at 321 cfm, which was more than enough to support the needs of our test motor. In a strange twist of fate, the small port volume and intake valve actually traded low-speed torque for the extra top-end power (compared with others in the test).
Test 7
TEA LS6
Retail price: $1,320 (porting on customer-supplied head castings)
Intake valve size: 2.055
Exhaust valve size: 1.575
Intake port volume: 226 cc
Exhaust port volume: 78 cc
Chamber volume: 63 cc
Peak power: 618.1 hp at 6,300 rpm
Peak torque: 555.3 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 476.1 hp
Average torque (3,000-6,500): 521.8 lb-ft
Torque at 4,000 rpm: 515.1 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 33 26 0.100 66 60 0.200 144 118 0.300 214 163 0.400 269 199 0.500 310 223 0.600 329 235 0.650 330 230 0.700 310 231
It seems like just about everyone with a grinder offers ported stock LS1/2/6 heads, so naturally we had to choose at least one set for our test. It didn't make much sense to have 20 to 30 sets of ported LS1/2/6 heads, so we decided to pick one set to represent what was possible with the factory castings. Naturally, we selected the cream of the crop in terms of factory castings-the LS6 head. Our ported LS6 heads came from the flow wizards at Total Engine Airflow. The TEA Stage 2 heads featured the requisite CNC porting, a 2.055/1.575 valve package, and 63cc combustion chambers. As delivered from TEA, the LS6 heads offer 330 cfm combined with impressive midlift flow numbers. It bears mentioning that the ported LS6 head was the lightest of the bunch, which as you know is the same as offering more power. Down just a few horsepower compared with the best of the bunch, porting a set of stock heads is obviously a very cost-effective alternative to purchasing new castings-especially if you already own a set of LS6 heads.
Test 8
Texas Speed 237
Retail price: $2,199
Intake valve size: 2.10
Exhaust valve size: 1.60
Intake port volume: 238 cc
Exhaust port volume: 85 cc
Chamber volume: 64 cc
Peak power: 621.3 hp at 6,700 rpm
Peak torque: 558.4 lb-ft at 5,300 rpm
Average horsepower (3,000-6,500): 477.5 hp
Average torque (3,000-6,500): 523.3 lb-ft
Torque at 4,000 rpm: 514.5 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 27 0.100 72 59 0.200 149 115 0.300 226 176 0.400 281 217 0.500 317 234 0.600 336 242 0.650 345 243 0.700 351 244
The 237cc Texas Speed heads were dedicated castings that offered not only exceptional flow numbers but also additional head boltholes for use on the aftermarket LSX blocks. If you go looking to make a serious turbo motor with a set of cathedral-port heads, the extra clamping force offered by these extra bolts might be just what you need. The TS heads combined a 2.10/1.60 valve package with a 238/85cc port volume package to maximize airflow. Next to the AFR 245 heads, the TS heads offered the highest 0.500-lift flow numbers. Power production was every bit as impressive, and the average numbers were bettered only by the Trick Flow GenX head.
Test 9
Trick Flow 235
Retail price: $2,550
Intake valve size: 2.08
Exhaust valve size: 1.60
Intake port volume: 234 cc
Exhaust port volume: 80 cc
Chamber volume: 64 cc
Peak power: 619.1 hp at 6,400 rpm
Peak torque: 558.2 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 478.4 hp
Average torque (3,000-6,500): 524.6 lb-ft
Torque at 4,000 rpm: 517.7 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 25 0.100 67 57 0.200 144 113 0.300 221 172 0.400 272 213 0.500 309 230 0.600 333 240 0.650 323 240 0.700 315 244
In the past we've exceeded 700 hp with Trick Flow Specialties' 245 heads on a larger 454ci stroker, so we were eager to see how the GenX 235 heads fared on our 408. The heads have a 2.08/1.60 valve package combined with an intake port volume of 235 cc (ours measured 234 cc) and took top torque honors among the cathedral-port heads, though by only 0.1 lb-ft. Is the highest peak power number the most important or is it the best average power production over a given range? The answer depends, which is why we provided both.
Test 10
West Coast Cylinder Head Edelbrock 245
Retail price: $2,385
Intake valve size: 2.08
Exhaust valve size: 1.60
Intake port volume: 243 cc
Exhaust port volume: 88 cc
Chamber volume: 64 cc
Peak power: 618.9 hp at 6,400 rpm
Peak torque: 554.0 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 475.5 hp
Average torque (3,000-6,500): 521.3 lb-ft
Torque at 4,000 rpm: 515.4 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 34 24 0.100 69 54 0.200 146 115 0.300 203 171 0.400 254 210 0.500 300 231 0.600 325 238 0.650 323 240 0.700 324 240
Not by design, we managed to wind up with not one but two different ported Edelbrock LS1 heads. Apparently, they are a popular starting point for serious CNC work. This pair came from the noted cylinder head specialists at West Coast Cylinder Heads. Like the ported heads from LPE, this pair featured 64cc combustion chambers but differed in both intake valve size (2.08 versus 2.10) and port volumes. The CNC program from WCCH produced larger intake and exhaust ports (measuring 243 and 88 cc). The larger ports seemed to improve flow, as the peak intake flow touched 325 cfm. The extra flow made itself known on the dyno as well. With the exception of the stock heads, every head tested produced peak torque either at 5,300 rpm or 5,400 rpm-interesting given the dramatic change in flow and port volumes. We can see why the Edelbrock heads are so popular among head porters.
Test 11
World Products Warhawk 255
Retail price: $2,790
Intake valve size: 2.10
Exhaust valve size: 1.60
Intake port volume: 255 cc
Exhaust port volume: 87 cc
Chamber volume: 64 cc
Peak power: 602.3 hp at 6,500 rpm
Peak torque: 542.2 lb-ft at 5,400 rpm
Average horsepower (3,000-6,500): 466.6 hp
Average torque (3,000-6,500): 512.3 lb-ft
Torque at 4,000 rpm: 506.0 lb-ft
FLOW DATA: CFM (AT 28 INCHES) LIFT INTAKE EXHAUST 0.050 35 25 0.100 63 56 0.200 137 115 0.300 200 165 0.400 260 198 0.500 297 214 0.600 313 224 0.650 324 228 0.700 328 233
The Warhawk heads from World Products are available in both as-cast 235 and 255cc CNC-ported versions. These heads offer a number of desirable features, including a 0.750-inch-thick deck surface to minimize distortion and maximize sealing, a raised valve cover rail to facilitate aftermarket valvetrain components, and Manley stainless steel valves to maximize flow. The CNC porting offered by Kuntz & Kraft on the Warhawk heads produced good flow numbers, peaking at 325 cfm. The World heads relied on a 2.10/1.60 valve combination. The one problem presented by the raised valve cover rail was it prohibited the use of roller rockers without grinding the valve cover rail. Since we didn't want to modify a head we planned on returning, we were forced to run factory rockers in place of the 1.72:1 roller rockers. Previous testing has shown the rockers to be worth 8 to 10 hp, so we figure these numbers are down somewhat from where they would be had we been able to run the roller rockers.
