Mine being a 350 HO came with it from the factory. I upgraded it for Pure Stock Racing to a Pypes 2 1/2 Mandrel bent X pipe system with the transverse muffler. It is tight and have to lower the X brace with the brackets provided.
IMO I wouldn't lower the X brace like that. And if I did I wouldn't brag about the clearance like on that web page. If you have stock manifolds you might as well put a stock dual exhaust on it. I have stock manifolds and exhaust that tucks up in the tunnel. My car still has plenty of performance and I have lots of clearance. I bet you will not gain any more than about 20HP between those headers and X pipe and my stock system. If you need the 20 bones that much then go for it!
To warm up the intake for emissions, yes (only between the center two cylinders). But it doesn't balance the exhaust pulses between both banks for improved scavaging if that is what you are implying.
If I recall, Jim Hand talks about the X crossover for it's ability to calm down the exhaust noise while maintaining performance. In the later parts of his book, he talks about the trade offs between exhaust configuration, noise and 1/4 mile times. I think the X crossover was a winner except for the complexity. And he was not discussing the Firebird where fit might be more difficult.
I would be interested in hearing about the concerns with Pypes system. If not their system, what will mail order and bolt on in the garage without hauling the project off to a shop on a roll-back?
To warm up the intake for emissions, yes (only between the center two cylinders). But it doesn't balance the exhaust pulses between both banks for improved scavaging if that is what you are implying.
it has always been my understanding that only the ford engines required a H-pipe.gm engines balanced the flow at the intake.but what do i know?the only time it was ever recommended in a gm motor was in conjunction with a cheap aftermarket manifold
To warm up the intake for emissions, yes (only between the center two cylinders). But it doesn't balance the exhaust pulses between both banks for improved scavaging if that is what you are implying.
it has always been my understanding that only the ford engines required a H-pipe.gm engines balanced the flow at the intake.but what do i know?the only time it was ever recommended in a gm motor was in conjunction with a cheap aftermarket manifold
Mopars used them from the factory too. In addition to balancing the pulses, it increases collector length.
I would love to hear the theory on how the intake flow balances the exhaust flow on a Pontiac. Please enlighten us.