Originally Posted by F-BIRD'88
Interesting. Looks like it is air flow limited s the torque at 5000rpm is equal. So it likely does not make any more peak horsepower than the stock manifold even thou it makes more low-mid power.
How does your manifold compare to a out of the box weiand tunnel ram?
We're not airflow limited on that engine.
Horsepower peak with the Street Ram was 286, vs. 274 with the Performer.
Where we did get into limitation is on the 350-inch 11:1 roller motor we ran. There the RPM air-gap style intake made 460HP peak vs. 440HP for our setup. We made more power everywhere below 4000RPM. So I'm thinking 450HP is about the limit of engines it makes sense to put this on.
We ran the regular Weiand top with a pair of 390CFM vacuum secondary carbs to give it the best possible chance on the mild engine. Those carbs are over $700 for a pair, so way more expensive than anything you get in the combo kits from Summit or Jegs. Our setup made 42lb-ft more torque at 1500RPM, 23lb-ft more at 2000, and keep making more up to 4000RPM where they crossed over. The regular top made more top-end power, but was mushy down low even with the small vacuum secondary carbs. If you put on the 450CFM mechanical secondary carbs you get in the kits, it would be terrible down low because the venturi velocity would be so bad.
This setup is so eager and responsive on the street. If you coudn't see the dual carbs you would swear it was a single four on a dual-plane.