Are H or X pipes really necessary?

Many know what my car is, right? A 64 Galaxie fastback with a 650 hp ish 514 ci., C6 tranny. OK, I want dual 3" stainless exhaust system. I get mixed answers on H pipes versus just one pipe per side, no connecting or crossover. Maybe it's more necessary on newer cars, no? I'm about to get an exhaust made so I'm kinda curious what the big deal is, that's all.

Yes and no! Ha ha, didn’t expect that answer...... Well, a crossover pipe really helps equalize your exhaust. It will help make your car quieter and will help scavenge the exhaust. So, it will help flow and sound. Personally, I love the sound of a V8 with out an x or h…. sounds raw and mean however, its un equal flow. My 66 Fast back sound SICK at all RPMs. No x or h and only a stock FE. My 64 has an H pipe sounds great an focused. My Mustang went from an H to something called a prochamber which is a box as apposed to an h or x. It is even quieter. It made 7 more HP over an X pipe.

Then there is the smarty answer. The convertbiles don't have either one. At least in '64. Not sure if it ever did or even supposed to with the frame the way they are.

H-pipes improve low end torque and make the exhaust somewhat less noisy. They also improve the integrity of the system. It is much less likely for something to work loose if it is all one piece. My car has a dummy H pipe. Got that big block rumble but yet it looks good and does not move around.

Someone PLEASE tell me HOW joining the left and right bank will help the flow of either bank?

Seems to me that the less each side has to work to get it out the better the flow would be...

Does the flow increase due to the straw holding water effect? Because of one cyl pushing out then the amount just ahanging there going nowhere until it opens and get's pushed again?

Gary-- the cross over works as scavenger-- it will pull the in coming air/fuel charge along with it as the in take and exhaust valves are both open at the same time -[overlap]-- its this short period of time just as the in take is opening

the exiting exhaust pulse will help getting the charge moving--
think of it as - as the exhaust leaves it causes a vacuum in the cylinder--

thats why headers are tuned by pipe length-- so the exhaust all travel the same distance keeping the flow [vacuum equal]--and at the right time to help the incomeing charge pack the combustion cylinder.--

Here is an article on H verses X pipe.
Exhaust System Installation H-Pipe, X-Pipe,- Car Craft Magazine

So really (in theory) an X-pipe is best, but for minimal gains. Basically any "joining" helps equalize pressure, back pressure I guess. However, it's like splitting hairs and with either x or h will quiet my ol Gal down (hum, not a fan of quieting a v-8 down) so I'll go with individual piping side by side. I kinda figured it wasn't a big deal in either setup, but thank you all for the feedback.

Somehow I don't think 514 needs the extra 7 horsepower.

Thanks Richard, that was what I needed to know.