1951 Dual Exhaust Conversion

[rvc_51]

I would like to convert my 1951 Coupe DeVille to dual exhaust.  I realize I will need to modify my chassis.  Would anyone know if I need different exhaust manifolds?  Anything else?  Thanks.

[CRAIG LEWIS]

I completed this conversion but used a 53 motor  it was a dual exhaust already. The manifold from the 51 leftr side crosses under  the engine and ties into the right side exhaust pipe. If you cut the left pipe out and disconnect it from the manifold,  you can probably just weld a new run of pipe straight from the manifold using a tub cut from the original crossover pipe..  I cut the x  member of the frame both front and back to fit the pipe through the frame to match the right side. no problems cutting the holes out should go easy I used a plasma cutter after marking pattern drawn from the other side. The trickiest part is where it runs back up over the rear axle since this is where the fuel line is. I routed my fuel line into a biger arc to be sure it was plenty clear of the pipe. It was a bit tight running past the tank. On the 52/53 the trunk is notched to allow the pipe past. i didnt need to but I suppose you could modify the trunk pan as week but it wa not necessary.

Good luck
Craig

[rvc_51]

Thanks Craig.  Would you know if the '53 exhaust manifolds I assume you used are different from the '51 manifolds I have?  Would you have casting/part numbers?  Thanks.

[Jay Friedman]

Beginning in '52 when dual exhausts became standard, exhaust valves were enlarged and exhaust manifolds changed.  (49-51 manifolds are part no. 145 3754 and 52-53 manifolds are 145 8736.)  It may be that the 52-53 manifolds will not bolt up to your '51 cylinder heads.  Using your '51 manifolds it seems from what Craig wrote to be lots of work to install duals.  In addition, I may be paranoid but it would make me nervous to have the new left side exhaust pipe anywhere near the fuel line or gas tank.

I'd like to suggest an alternative.  This is to keep a single exhaust but install a larger diameter exhaust pipe.  The stock exhaust manifold internal diameter is 2 1/8 inches.  This narrows down to a 2 inch diameter in the pipe itself.  It is possible to purchase and install a 2¼ inch pipe without much, if any, additional cost over a 2 inch pipe.  Doing this will give the pipe a 26% greater internal cross section and allow the engine to breath easier without much additional work or change in appearance.  A friend did this on his '49 with good results.

[rvc_51]

Jay, thanks for the part number information and the idea.  Based on the part numbers you gave, the left and right manifolds are the same?  Thanks.  Rick   

[Jay Friedman]

Sorry, Rick, I must have been in an old age fog when I wrote the part numbers.  Let me start over:

1949-51: right exhaust manifold is 145 3961; left is 145 3754.

1952-53: right exhaust manifold is 145 8736; left is 146 1495.  (This left one was also used through '55.)

Jay