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Make 561 HP Using AFR Composite Intake Manifold

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The Heads
To make this test even spicier, we included a new set of AFR 195cc Competition ported heads that sport an upgraded CNC program that should be available from AFR by the time you read this. Mamo claims that with some minor tweaks, he's been able to improve the flow numbers by a couple of percent, yet the price and the part numbers for the Competition ported heads remain the same. So if you've been putting off buying a set of heads, then now's the time. Mamo says the heads will flow in excess of 300 cfm at more than 0.600-inch lift, which is on the ragged edge of what might be considered streetable, but our test with 0.555-inch intake lift was enough to push our 383 to 560 hp, so the potential is real.

The Engine
In a previous life, our test engine was a GM Performance Parts HT 383 with a mild Comp hydraulic roller cam, a set of TFS 210cc heads, an Edelbrock Performer RPM Air-Gap dual-plane, and a 750-cfm Holley that made a respectable 490 hp and more than 500 lb-ft of torque. We began our tune-up with a bigger Comp Xtreme Energy 288 hydraulic roller cam. For heads, it only seemed fitting to use a set of AFRs, and Mamo offered to let us test a brand-new set of revised AFR Competition CNC-ported 195 heads that should be available by the time you read this. However, since our engine is still running hypereutectic pistons and stock rods, we elected to keep the peak power below 6,500 rpm.

Test Day
To get a sense of how well both Titan intake manifolds worked, we needed a solid baseline for comparison. When it comes to small-block Chevy single-plane intake manifolds, the accepted benchmark has to be the Edelbrock Victor Jr. This manifold has been around for nearly two decades and continues to be a small-block performance standard. From a carburetor height standpoint, the Titan TXS is closest in terms of runner length while the TXR is more than an inch taller, benefiting from longer runners that improve midrange torque. The veteran Victor Jr. made excellent power, cranking 504 lb-ft for torque and an outstanding 531 hp at the peak. We then swapped to the Titan TXS and the overall power picked up across the board. Perhaps the most impressive gain was the 19hp peak bump from 531 to 550 hp, but the average torque also improved 9 lb-ft. So it wasn't too surprising that the taller Titan TXR intake performed even better. Right from the start of the test at 3,000 rpm, the taller Titan produced double-digit torque increases over both the shorter Titan TXS and the Victor Jr. The chart's "Difference" column shows the total TXR improvement over the baseline. Average torque for the TXR also increased, showing a 9-lb-ft average gain over its shorter TXS cousin and an impressive 18 lb-ft compared with the Victor Jr.

We also tested the manifolds at a higher engine coolant temperature to see if we could measure a composite power increase over aluminum, but the percentage of gain of the composite versus aluminum really didn't reveal very much. However, under normal street driving, we think it's possible that the composite material will maintain a cooler intake air temperature.

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Car Craft