So my car is in my friends shop today getting duals put on. I didn't realize the manifold configuration as it was a single exhaust and it's all original. Instead of all the hassle of capping the second port and trying to route the new exhaust pipe from the driver side down and behind the steering linkage, could one just add a Y pipe after the passenger side exhaust port to go to two pipes from there? Basically a similar idea to an X Pipe, no? Car is 365 HP 455, 31k original miles.

 

If you want true duals do it factory style, get the correct manifold for the left side, capping the crossover port on the passenger side is easy. The end result will look so much nicer and perform better as well.

 

Mendozza, you can weld a Y into the passenger's side exhaust pipe if that's what you want to do. It would probably be cheaper because you wouldn't have to buy a reproduction Thronton's manifold. However, it might no be as good for HP and torque gains. Nothing you will be able to detect with the butt dyno though.

 

I did the conversion on my 67 with the Thorntons manifold. This is the right way to go. My car actually had a half-fast dual installation using the original center dump LH manifold when I got it. The pipe was almost completely flattened to clear the starter and steering linkage. It probably made LESS HP than with the original single exhaust. Note that the factory dual exhaust cars also had a unique trans shift linkage to increase clearance to the LH pipe. Mine clears fine with the original linkage. Capping the RH crossover port was trivially easy. Note that the available cap for the 350 cars does NOT fit the BBO manifolds. You need to fabricate a cap. Also, unlike the A-body manifolds, these do use donuts to seal to the pipes.