I just picked up a 99 GMC Sierra w/ a 5.3L today. I won't be buying another intake manifold anytime soon, but I thought that if the LS1 intake flowed better than the 5.3L intake, I have one laying in my garage that I could swap out in about an hour. Is it worth it? Does the LS1 intake outflow the 5.3L intake? I would think the 5.3L would flow better or about the same, but that's just speculation. Any ideas? Thanks in advance.

 

The truck intake is designed to provide more low end torques vs. the LS1 intake that gives more top end power. You will probably gain some hp in the upper rpm range with the LS1 intake but loose some torque below 3000 rpm. In old SBC terms it is basically like comparing a good dual plane intake to a decent single plane intake.

 

Thanks for the input. I reckon I'll just stick with the 5.3L intake then. Just got to thinking about swapping since I had an extra intake laying around. Just wasn't sure about the differences between the two.