Gain from longtubes
Before my gear swap with full exhaust, lid, self-ported tb, and tune. It made 354/373 and ran 12.5s@112. In the end with the above and 4.10s it went 12.3s@113.
Just adding the full exhaust didnt add a whole lot, (only about 15rwhp/16rwtq), it was the tune and everything working together that made the numbers and ran the times.
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I thought full exhaust would gain at least 20hp
Now the thing that I can't help to consider is how much would have been gained just with a tune; a good tune that can move the power curve to produce better traction at the best moments. Because it came after the header installation and there was no time slips for just the headers there is no way to know exactly what the headers actually benefit. Like the posts above, the responses are visceral and combined with other modifications. Keep in mind that those LS1 manifolds are notoriously efficient breathers and it is hard to beat them for durability.
Since I live in a land where emission testing is mandatory and long tubes will void my ability to get licensed I have to limit my mods to the exhaust after the catalyst. BTW, shorties on an LS1 are just not worth it to me and like the article stated, some feel the LS1 manifolds actually produce more power than many short tubes that are available.
Here's why the near stock LS1 makes such great power with a factory manifold.

nice times by the way, what is the break down of your car, weight DA conditions, mods, etc







