'36 Terraplane exhaust question

terraplane8

Can anyone help on the pipe diameter as originally specified for the '34-'36 six cylinder engines? The current tailpipe is 1 and 3/4 inches OD which does seem somewhat small for 3.5 litres to exhaust through. The engine doesn't like to go over 40mph in second and 70mph in top and this is one item to check out. I would have thought 46 and 81 were achievable, ie 15% higher engine revs. The engine is in very good condition with great torque on hills at 40-55 in top.



And also, was the front pipe meant to be the same or larger diameter as the tailpipe, as the current front pipe is a fair bit smaller than the exhaust manifold outlet flange diameter.



Lastly what is the best replacement muffler to fit the (tight) space that will allow good flow?