Test 1: Baseline—Stock 350 Chevy 5 Our 350 test mule was equipped with a set of forged flat-top pistons from Probe Racing. The valve reliefs provided sufficient clearance for our eventual high-lift cams.5 Our 350 test mule was equipped with a set of forged flat-top pistons from Probe Racing. 6 Equipped with the 882 iron heads, cam, and Q-Jet intake, the stock 350 produced 279 hp at 4,500 rpm and 385 lb-ft of torque at 3,300 rpm.6 Equipped with the 882 iron heads, cam, and Q-Jet intake, the stock 350 produced 279 hp 7 Graph 1: Stock 350 Starting with a basic 350 with flat-top pistons, we first equipped it with a stock hydraulic flat-tappet cam (the engine was rated at 180 net hp when new), a set of stock iron 882 heads, and Q-Jet intake and carb. Not surprisingly, these stock components produced plenty of torque (385 lb-ft at 3,300 rpm) but very little peak horsepower (just 279 at 4,500 rpm). That the peak power came at just 4,500 rpm was a clear indication that the stock heads, cam, and intake were all designed with low-speed torque in mind. There are obviously more powerful factory cam profiles (the Duntov 30-30 for instance), but we chose these specs to represent what you might find in a fullsize car or truck at your local wrecking yard.7 Graph 1: Stock 350 Starting with a basic 350 with flat-top pistons, we first equipped Baseline 350 Engine Specs Short-block 350 Chevy flat-top pistons Heads: stock 882 iron 1.94/1.5 valves Cam: Stock hyd. flat-tappet {factory 180hp} Rockers: Stock Intake: Factory iron Q-Jet Carb: Factory Q-Jet Exhaust: 1-5/8-inch headers Test 2: Stock vs. Ported Heads, RV Cam, and RPM Air Gap 8 Our first upgrade included porting the 882 heads and stepping up to a larger 2.02/1.60 valve package.8 Our first upgrade included porting the 882 heads and stepping up to a larger 2.02/1.60 9 In keeping with the mild theme, we chose a PE246H cam from the Comp Cams catalog. The PE246H was an emissions-legal cam upgrade for 1987-and-earlier small-blocks.9 In keeping with the mild theme, we chose a PE246H cam from the Comp Cams catalog. The P 10 The final components included an Edelbrock Performer RPM Air Gap intake and 650 Demon carb. The ported stock heads with bigger valves, mild cam, and induction upgrade improved the power output from 279 hp and 385 lb-ft to 364 hp and 422 lb-ft. The performance package improved the power output through the entire rev range.10 The final components included an Edelbrock Performer RPM Air Gap intake and 650 Demon 11 Graph 2: 350 Chevy— Stock vs. Upgrade 1 The first upgrade performed to the 350 was to replace the stock cam with what is commonly called an RV grind (Comp PE246-0.429/0.438 lift, 203/212 duration, and 110 LSA). To the cam swap we added a set of mildly ported 882 heads (2.02/1.6 valves) and a Performer RPM Air Gap and Demon 650 carb. The mild upgrades improved the power output substantially, and the power improved throughout the rev range. It goes to show what can be accomplished while retaining the stock heads. The PE246 cam is pretty mild for a 350.11 Graph 2: 350 Chevy— Stock vs. Upgrade 1 The first upgrade performed to the 350 was to 12 The next performance package for our 350 included a set of aluminum 190cc heads from Procomp Electronics. The as-cast heads were not only affordable, they flowed significantly better than our ported stock heads.12 The next performance package for our 350 included a set of aluminum 190cc heads from P Test 3: Stock vs. Procomp Electronics Aluminum Heads, Comp Cam, and RPM Air Gap 13 The aluminum heads were once again teamed with the RPM Air Gap intake, though we replaced the Demon carb with a 650 Holley.13 The aluminum heads were once again teamed with the RPM Air Gap intake, though we repla 14 To take full advantage of the additional head flow, we installed a slightly wilder cam profile. According to Comp Cams, the XE268H is the favorite small-block performance cam, offering the ideal combination of performance and driveability.14 To take full advantage of the additional head flow, we installed a slightly wilder cam 15 Run with the aluminum heads, XE268H cam, and Edelbrock intake, the 350 pumped out 420 hp at 5,600 rpm and 444 lb-ft of torque at 3,900 rpm. Note that horsepower was up by 56, while peak torque improved by just 22 lb-ft. We were starting to shift the curve.15 Run with the aluminum heads, XE268H cam, and Edelbrock intake, the 350 pumped out 420 16 Graph 3: 350—Stock vs. Upgrade 2 Upgrade 2 consisted of a set of 190cc as-cast aluminum heads from Procomp Electronics, a slightly wilder (though perfectly streetable) XE268H cam, and Performer RPM Air Gap intake. Replacing the factory Q-Jet was a Holley 650 carb. If your engine spends most of its time below 4,500 rpm, the factory Q-Jet intake works very well. The aluminum version is obviously desirable for the weight savings, but the Air Gap is significantly better at higher engine speeds. Obviously the aluminum heads from Procomp Electronics handily outflowed the factory castings (even ported 882s) while also increasing the compression ratio thanks to 64cc combustion chambers. A perennial favorite among Chevy owners, the Comp XE268H cam offered a 0.477/0.480 lift split, a 224/230 duration split, and the same 110-degree LSA as the previous PE246H cam. The combination of aluminum heads, XE268H cam, and RPM Air Gap intake netted impressive results. The peak power of this combination checked16 Graph 3: 350—Stock vs. Upgrade 2 Upgrade 2 consisted of a set of 190cc as-cast aluminu 17 For the final package, we installed a set of 195 Eliminator heads from Air Flow Research. Wanting to maximize airflow and power, we stepped up to the available Competition version.17 For the final package, we installed a set of 195 Eliminator heads from Air Flow Resear Upgrade 2, 350 Engine Specs Short-block 350 Chevy flat-top pistons Heads: Procomp aluminum 190cc heads {as cast} 2.02/1.6 valves Cam: Comp XE268H {0.477/0.480 lift, 224/230 duration, 110 LSA Rockers: Comp Roller 1.5 Intake: Edelbrock Performer RPM Air Gap Carb: Holley 650 Exhaust: 1-5/8-inch headers Test 4: Stock vs. Airflow Research 195 Eliminator Heads, Comp Hyd. Roller Cam, and AFR Titan Intake 18 Thanks to extensive CNC porting and a 2.08 intake valve, the AFR Eliminator heads flowed over 300 cfm (enough to support in excess of 600 hp).18 Thanks to extensive CNC porting and a 2.08 intake valve, the AFR Eliminator heads flow 19 Replacing the XE268H cam was a serious stick in the form of an XR300HR. The retrofit hydraulic roller offered a 0.562/0.580 lift split, a 248/254 duration split, and 110-degree LSA. This would be considered a wild cam for a street small-block displacing 350 cubic inches.19 Replacing the XE268H cam was a serious stick in the form of an XR300HR. The retrofit h 20 The ARF heads and Comp Hydraulic roller cam were teamed with a new Titan single-plane intake manifold. Like the heads and cam, the intake was designed to maximize power higher in the rev range.20 The ARF heads and Comp Hydraulic roller cam were teamed with a new Titan single-plane 21 Run on the dyno, this final performance package produced 542 hp at 6,300 rpm and 477 lb-ft of torque at 5,100 rpm. With this final combination, we improved the power output by 263 hp and 92 lb-ft from stock and shifted where the motor made peak power (and torque) by 1,800 rpm.21 Run on the dyno, this final performance package produced 542 hp at 6,300 rpm and 477 l 22 Graph 4: 350 Stock vs. Upgrade 3 This is where things start to get serious. The output suggest that this buildup was the most successful, but only if you go by peak power alone. The upgrades included a set of AFR 195 Eliminator heads (competition version), a wild XR300HR hydraulic roller cam (0.562/0.580, 248/254 duration, and 110 LSA), and new AFR Titan composite intake. Equipped as such, the 350 produced 542 hp and 477 lb-ft of torque. Impressive to be sure, but the motor didn't really come on the cam until the tach needle passed 4,500 rpm. This combination would be much more at home on the strip than on the street. This combination pushed the peak power output to 6,300 rpm, up from 5,600 with the previous package. Basically the power gains come from effectively shifting the torque curve higher in the rev range. The downside to the extra power is usually a low in low-speed torque. Combine the AFR 195 heads with a milder cam and a solid dual-plane intake (AFR has a composite dual-plane in22 Graph 4: 350 Stock vs. Upgrade 3 This is where things start to get serious. The output Upgrade 3, 350 Engine Specs Short-block 350 Chevy flat-top pistons Heads: AFR 195 Eliminator heads {Comp version} 2.08/1.6 valves Cam: Comp XR300HR {0.562/0.580 lift, 248/254 duration, 110 LSA Rockers: Comp Roller 1.5 Intake: AFR Titan Composite Single-Plane Carb: Holley 950 HP Exhaust: 1-3/4-inch headers SOURCES Edelbrock 2700 California St. Torrance CA 90503 310-781-2222 www.edelbrock.com L&R Automotive 13731 Bora Drive Sante Fe Springs CA 90670 562-802-0443 www.lnrengine.com Air Flow Research 28611 W. Industry Drive Valencia CA 91355 877-892-8844 www.airflowresearch.com Probe Racing 2555 West 237th Street Torrance CA 90505 310-784-2977 www.probeindustries.com Comp Cams/Fast 3406 Democrat Road Memphis TN 38118 800-999-0853 www.compcams.com Procomp Electronics 605 S. Milliken Avenue Unit A Ontario CA 91761 909-605-1123 www.procompelectronics.com Holley/Hooker 1801 Russellville Road Bowling Green KY 42101 270-782-2900 www.holley.com « | 1 | 2 | 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!
