hello there i have a 1977 plymouth volare slant six w/ dual barrel carb. i took it for about a 10 mile drive and noticed on the way back this loud noise that sounds like the pistons firing normally(just extra loud). i have checked all of the spark plugs and they are fine. i am curious as to weather it is an exhaust gasket that has cracked, or if it is a bolt that has come loose. i have a video of the sound if any one is interested in hearing it please email me at zane.giust@gmail.com and i will reply with the video. thank you

Take a good look at the exhaust manifold. They are known to crack. Usually the crack is fairly obvious.

- Mac

Hello and welcome. Could be cracked manifold, could be blown gasket at the manifold to head surface or the exhaust manifold to exhaust pipe surface. Could also be very misadjusted valves.