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Speed Secrets: FAST LSXR 102mm Intake Test!

How much power are intake manifolds really worth is a commonly asked question. To try his hand at answering this question, Richard Holdener with Speed Secrets teams up with Comp Cams and Fast. The problem with this question is that even though it seems pretty straight forward, it’s really not. The reality is that the power gains from an intake manifold varies from engine to engine. For instance, if you were to compare a Fast intake with a factory GM truck intake on a stock LS based 4.8L or 5.3L, the gains would be minimal. Thats not because the Fast manifold doesn’t work but because the stock manifold works very well. However if you were to add a camshaft and cylinder head combination to the same test engine, the power gains offered by the Fast intake would be dramatic. Now if you stepped things up with say a modified 6.0L, the gains would only increase. Because seeing is believing, Richard tests this theory on two engines. First on a 5.3L and then on a 6.0L. 

The 5.3L featured a stock bottom end, a set of ported TEA 706 heads, and a healthy Comp camshaft – 54-454-11 with a .613/.623 lift, 227/243 duration, and 113 LSA. First run on the Dyno, the 5.3L equipped with a factory truck intake manifold produced 464 HP and 414 Lb-Ft of torque. However, after installing the Fast manifold with a 102mm throttle body the 5.3Ls power output jumped to 492 HP and 422 Lb-Ft of torque. That represents a gain of 28 HP and 8 Lb-Ft of torque from the manifold alone. With impressive gains on the 5.3L, it’s time to see how displacement plays a role in intake function. 

The 6.0L featured a forged rotating assembly with flat top pistons and Airflow Research heads. Also installed was a Comp 54-469-11 cam that featured a .617/.624 lift, 231/247 duration, and 113 LSA. Equipped with the factory truck intake the modified 6.0L produced 549 HP and 481 Lb-Ft of torque. Once again, after the installation of the Fast intake with a 102mm throttle body the power output jumped to 591 HP and 505 Lb-Ft of torque. On this 6.0L the Fast LXSR intake manifold was worth an additional 42 HP and 24 Lb-Ft of torque. Proving that the Fast LXSR intake is worth some serious power, and even further that stepping it up in displacement allows for even more power gains from the Fast LXSR. 

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The 6.0L featured a forged rotating assembly with flat top pistons and Airflow Research heads. Also installed was a Comp 54-469-11 cam that featured a .617/.624 lift, 231/247 duration, and 113 LSA. Equipped with the factory truck intake the modified 6.0L produced 549 HP and 481 Lb-Ft of torque. Once again, after the installation of the Fast intake with a 102mm throttle body the power output jumped to 591 HP and 505 Lb-Ft of torque. On this 6.0L the Fast LXSR intake manifold was worth an additional 42 HP and 24 Lb-Ft of torque. Proving that the Fast LXSR intake is worth some serious power, and even further that stepping it up in displacement allows for even more power gains from the Fast LXSR. 

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