Small-Block Bolt-Ons - Chevys Gone Wild

Making a mundane two-barrel small-block into a spicy meatball

Richard Holdener Aug 15, 2006 0 Comment(s)

Graph 1: Stock Air Cleaner vs Comp Cams Open Element

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Graph 1: Stock Air Cleaner vs Comp Cams Open Element

For our first test, we replaced the stock single-snorkel air filterassembly (with new paper filter element) with a composite unit from CompCams. The Composite air filter assembly was designed to mount on our 2GRochester two-barrel and provided an unobstructed flow of air into thecarburetor. Data logging showed that the new air filter dropped themanifold vacuum (surefire evidence of an airflow restriction) from 5.5inches (with the stock filter assembly) down to 4.5 inches. Thereduction in manifold vacuum brought with it an increase in power, inthis case from 229 hp and 350 lb-ft of torque to 241 hp and 359 lb-ft oftorque.

Graph 2: Stock Exhaust Manifolds vs Flow Tech Headers

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Graph 2: Stock Exhaust Manifolds vs Flow Tech Headers

With the small-block only producing 241hp, we didn't really expect tomuch of a power gain from replacing the cast-iron exhaust manifolds withthe Flow Tech headers, but we knew they would show huge dividends laterin our testing. The headers were installed using the same Hooker2.5-inch exhaust system, minus the 90-degree bends used with the stockmanifolds. Running the long-tub headers resulted in an increase in peakpower from 241 hp and 359 lb-ft of torque to 248 hp and 366 lb-ft oftorque. Note that the headers improved power production across the revrange-always a good sign.

Graph 3: Stock Two-barrel Carb and Intake vs. Four-barrel Q-Jet and Intake

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Graph 3: Stock Two-barrel Carb and Intake vs Four-barrel Q-Jet and Intake

The power gains started to get serious with the introduction of thefactory cast-iron Q-Jet intake and matching 750-cfm (SMI rebuilt) Q-Jetcarb. The peak numbers were up from 248 hp and 366 lb-ft of torque to287 hp and 372 lb-ft of torque. The four-barrel induction reduced themanifold vacuum down to 0.5 inches, which explains the impressive powergain. Check out the solid gain of 30-35 lb-ft of torque from 3,200 rpmto 5,000 rpm. You'd certainly be able to feel a power gain of thismagnitude.

Graph 4: Q-Jet Cast Iron Intake vs Weiand 8004 Aluminum Intake

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Graph 4: Q-Jet Cast Iron Intake vs Weiand 8004 Aluminum Intake

This next test illustrated just how difficult it is to better thefactory cast-iron intake at low rpm. Installation of the Weaind 8004aluminum improved the peak power from 278 hp to 287, but peak torqueproduction was down from 385 lb-ft. to 372 lb-ft. In fact, the entirecurve was down from 2,200 rpm to 4,100 rpm, though there was very littledifference down below 3,000 rpm. This test is classis example of why Iinclude full graphs with all of my testing. Judging by just the peakhorsepower numbers, you'd be accurate to say the Weiand improved thepower output. Judging by the peak torque numbers, you'd be equallyaccurate to say the Weiand lost power. Which is right? Only by viewingthe entire curve can we see that both statements are correct.

Graph 5: Stock 882 Iron Heads & Cam vs Ported 882 Power Heads & PE246 Cam

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Graph 5: Stock 882 Iron Heads & Cam vs Ported 882 Power Heads & PE246 Cam

While the torque production of this small-block was always impressive,we were getting tired of seeing the peak power output climb oh-so-slowlytoward the 300hp mark. That situation quickly rectified itself after theinstallation of the next performance components. Off came the stock 882heads and 180-hp factory hydraulic flat-tappet cam an in their placewent an emissions legal PE246 cam and a set of ported (and big-valve)882 heads from Power Heads. Obviously the combination worked welltogether, as the new cam and ported stock heads improved the peak poweroutput from 287 hp to a whopping 340 hp. The heads and cam improvedhorsepower production by as much as 60 hp and 63 lb-ft of torque. Thetorque production took a healthy jump as well, from 372 lb-ft to an even400 lb-ft, with substantial torque improvements even down at 2,500 rpm.

Graph 6: Weiand 8004 & Q-Jet vs Edelbrock Performer RPM & Barry Grant 650 Demon

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Graph 6: Weiand 8004 & Q-Jet vs Edelbrock Performer RPM & Barry Grant 650 Demon

The final test for part one of Chevy Gone Wild involved replacing thecurrent induction system with an Edelbrock Performer RPM Air Gap andBarry Grant 650 Mighty Demon carb. Off came the Weiand 8004 and stockQ-Jet and on went the new components. The motor responded very well tothe new performance induction system, as the peak power numbers jumpedfrom 340 hp and 400 lb-ft of torque to 364 hp and 422 lb-ft of torque.Torque production on the 355 (0.040 over) small-block now exceeded 400lb-ft from 2,900 rpm to 4,700 rpm. We were pleasantly surprised that thehigh-performance induction system lost no power to the Weaind and Q-Jeteven down as low as 2500 rpm. With 364 hp and 422 lb-ft of torque, wehave come a long way from the 229 hp and 350 lb-ft of the originaltwo-barrel test motor, but there is even more power to be had from thissmall-block in the next issue.

Sources

Comp Cams
Memphis, TN 38118
800-999-0853
http://www.compcams.com
Barry Grant
Dahlonega, GA 30533
706-864-8544
www.barrygrant.com
Coast High Performance
Torrance, CA 90505
310-784-1010
www.coasthigh.com
Sean Murphy Induction
Huntington Beach, CA 92647
Fel Pro
Ashland, MS 38603
662-224-8972
federal-mogul.com
Power Heads
Fullerton, CA 92832
714/992-4909
www.powerheads.com

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