Test 1: Stock GM 088 Iron Prior to running any of the aftermarket heads we had to establish a baseline by running the stockers. We chose a set of 088 castings that featured 316cc intake ports, 121cc exhaust ports and 123cc combustion chambers. The airflow data suggested that the stock iron heads would support over 650 hp, but on this 496, the heads managed to produce peak numbers of 630 hp at 6,600 rpm and 577 lb-ft of torque at 5,300 rpm. While 630 hp would make a serious street motor, we would see that the right head choice on this application would add nearly 100 hp to that total. GM rectangular port castings Retail Price-NA Intake Valve Size-2.19 Exhaust Valve Size-1.88 Intake Port Vol-316 cc Exhaust Port-121 cc Chamber Volume-123 cc Peak Power- 630 @ 6,600 rpm Peak Torque- 577 lb-ft @ 5,300 rpm Avg HP (3,500-6,500)-532.4 Avg TQ (3,500-6,500)- 560.5 lb- TQ @ 4,000 RPM - 562.7lb-ft Flow Data: CFM @ 28-ins Stock 088 Lift In Ex 0.0503227 0.1007756 0.200144112 0.300206142 0.400245166 0.500289188 0.600320192 0.700334197 0.800335201 Test 2: Summit Racing Iron Many would dismiss the iron heads simply for the weight savings, but don't count them out, especially when you consider the price and performance. These rectangular port iron heads from Summit Racing offered surprising bang for the buck. The Summit Racing head upgrade improved the power output of the 496 from 630 hp and 577 lb-ft to 688 hp and 607 lb-ft. This was all the more impressive considering the fact that the heads cost just $750 bucks each, assembled. Toss in the fact that the Summit heads flow only marginally better than the stock heads and share the same combustion chamber volume. If you are looking for iron heads on a budget, look no further than Summit Racing. Retail Price-$749 Intake Valve Size-2.25 Exhaust Valve Size-1.88 Intake Port Vol-309 cc Exhaust Port Vol-127 cc Chamber Volume-122 cc Peak Power- 688 hp @ 6,600 rpm Peak Torque- 607 lb-ft @ 5,400 rpm Ave HP (3,500-6,500)-555.5 Ave TQ (3,500-6,500)-582.1 TQ @ 4,000 RPM-563.3 lb-ft Summit Racing Iron Flow Data: CFM @ 28-ins Lift In Ex .0503434 .1006969 .200146109 .300204155 .400264192 .500309223 .600340246 .700323262 .800330273 Test 3: Procomp Electronics Rec-Port CNC The aluminum heads from Procomp Electronics combined the largest port volume and (nearly) peak flow numbers with the lowest retail cost. The intake port volume measured a sizable 369cc, while the exhaust checked in at 157cc. This head configuration would be much more at home on a larger displacement, higher horsepower application, but how can you argue with aluminum BBC heads that flowed over 400 cfm for around $600? Equipped with the Procomp heads, the BBC stroker pumped out 690 hp and 600 lb-ft of torque. We suspect the large port volume and sizable combustion chamber hurt torque and power on this application, as many of the other heads featured smaller chambers and port volumes. We'd like to see this head strut its stuff on a high-compression 572, but for our 496, it was likely just too big. Retail Price-$625 Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-369 cc Exhaust Port Vol-157 cc Chamber Volume-123 cc Peak Power- 690 hp @ 6,300 rpm Peak Torque- 600 lb-ft @ 5,500 rpm Ave HP (3,500-6,500)-554.2 hp Ave TQ (3,500-6,500)- 581 lb-ft Tq @ 4,000 RPM-568.3 lb-ft Procomp Electronics BBC Rec-Port CNC Flow Data: CFM @ 28-ins Lift In Ex .0503531 .1007067 .200152132 .300234175 .400294206 .500336231 .600364251 .700389267 .800403279 Test 4: Trick Flow Specialties PowerPort 360 Heads Like the Procomp heads, the PowerPort 360s from Trick Flow Specialties were probably a tad on the big side for the 496. With intake ports that measured 357cc, the impressive PowerPorts would be more at home on a big-block exceeding 500 cubic inches. With peak intake flow numbers of 384 cfm, the heads we capable of supporting over 750 hp, but on our 496 manage 691 hp and 603 lb-ft of torque. The PowerPort heads shared the large (122cc) combustion chamber volume of the stock heads and came in at a cost-effective $1,229 (through Summit Racing). Retail Price-$1229 Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-357 cc Exhaust Port Vol-134 cc Chamber Volume-122 cc Peak Power- 691 hp @ 6,400 rpm Peak Torque- 603 lb-ft @ 5,400 rpm Ave HP (3,500-6,500)-555.3 Ave TQ (3,500-6,500)- 581.9 lb-ft TQ @ 4,000 RPM-562.3 lb-ft Trick Flow Specialties PowerPort 360 head Flow Data: CFM @ 28-ins Lift In Ex .0503530 .1007261 .200148125 .300217168 .400275198 .500325227 .600360246 .700376261 .800384273 Test 5: Brodix BB-3 Xtra 332 The new Brodix BB-3 Xtra 332 heads were not quite a rec-port head nor were they a conventional oval (or peanut) port head. They were somewhere in the middle, more like a rectangular-port with rounded corners. In truth, use of the 454-R (rec-port) intake may have hindered the power potential of the Brodix heads more than others due to the port mismatch. One thing for certain is that the Brodix heads topped all comers in terms of airflow with peak numbers of 409 cfm. Capable of supporting over 800 hp, our 496 produced 705 hp and 624 lb-ft of torque. We would love to port-match an intake to these heads in an attempt to translate all that airflow potential into power. Retail Price-$1840 Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-335 cc Exhaust Port Vol-133 cc Chamber Volume-115 cc Peak Power- 705 hp @ 6,400 rpm Peak Torque- 624 lb-ft @ 5,200 rpm Ave HP (3,500-6,500)-574.6 Ave TQ (3,500-6,500)- 602.7 lb-ft TQ @ 4,000 RPM-585.7 lb-ft Brodix BB-3 Xtra 33 Flow Data: CFM @ 28-ins Lift In Ex .0503331 .1006669 .200147120 .300211173 .400273221 .500333256 .600380277 .700409286 .800403296 Test 6: Dart Pro 1 335 The Pro 1 name from Dart has always meant power and this test illustrates that the name still carries some weight. For our street/strip 496 BBC, Dart supplied a set of its CNC-ported 335 heads. With flow numbers that reached nearly 400 cfm, the Dart Pro 1s were another set of 800-hp heads in search of a motor. The Dart Pro 1 heads featured rolled valve angles and raised exhaust ports to improve flow and power, but remained compatible with stock accessories. Run on the dyno, the big-block produced 717 hp and 619 lb-ft of torque. Equipped with a smaller chamber shared by the AFR and Edelbrock heads, the Dart would likely be right in the hunt for maximum power. Retail Price-$2021 Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-303 cc Exhaust Port Vol-137 cc Chamber Volume-122 cc Peak Power- 717 hp @ 6,500 rpm Peak Torque- 619 lb-ft @ 5,600 rpm Ave HP (3,500-6,500)-568.0 Ave TQ (3,500-6,500)-594.3 lb-ft TQ @ 4,000 RPM-572.5 lb-ft Dart Pro 1 335 Flow Data: CFM @ 28-ins Lift In Ex .0503429 .1006961 .200148125 .300228181 .400294219 .500336249 .600376271 .700398281 .800399289 Test 7: Edelbrock E-CNC 355 Edelbrock has stepped up in a big way recently with new performance offerings and these E-CNC 335 heads are a perfect example. Proudly made in the USA, the E-CNC heads offered plenty of flow, peaking at 391 cfm on the intake and 285 cfm on the exhaust. Sporting the smallest combustion chamber of the bunch at 107cc, the Edelbrock heads produced the highest static compression ratio. Naturally this helped power, allowing the E-CNC heads to produce 723 hp and 627 lb-ft of torque. Retail Price-$1,630 (required spring upgrade) Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-353cc Chamber Volume-107 cc Exhaust Port Vol-135 cc Peak Power- 723 hp @ 6,500 rpm Peak Torque- 627 lb-ft @ 5,600 rpm Ave HP (3,500-6,500)-573.5 hp Ave TQ (3,500-6,500)- 599.9 lb-ft TQ @ 4,000 RPM-574.0 lb-ft Edelbrock E-CNC 355 Flow Data: CFM @ 28-ins Lift In Ex .0503329 .1007361 .200148132 .300224185 .400283226 .500334252 .600364270 .700385278 .800381285 Test 8 AFR Magnum 300 Oval It takes more than just big flow numbers to make power, and these Airflow Research heads proved that. In fact, when asked to supply rec-port heads for this test, they opted to instead send over a set of oval-port heads. It new 300cc Magnum heads did not offer the highest peak flow numbers, topping out at 383 cfm (at .650 lift), but when combined with exceptional mid-lift flow and an efficient chamber design, the results were enough impressive. Power production is all about the combination of components working together and on this 496, the AFR Magnum 300 heads proved to be the optimum combination by producing 729 hp and 639 lb-ft of torque. Retail Price-$1,559 Intake Valve Size-2.30 Exhaust Valve Size-1.88 Intake Port Vol-300 cc Exhaust Port Vol-123 cc Chamber Volume-110 cc Peak Power- 729 hp @ 6,500 rpm Peak Torque- 639 lb-ft @ 5,400 rpm Avg HP (3,500-6,500)-584.1 Avg TQ (3,500-6,500)-611.4 lb-ft TQ @ 4,000 rpm-587.0 lb-ft AFR Magnum 300 Oval Flow Data: CFM @ 28-ins Lift In Ex .0503432 .1007462 .200153126 .300233198 .400296237 .500345263 .600377277 .700371288 .800365296 « | 1 | 2 | 3 | » | View Full Article By Richard Holdener Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!