Early or Late 4-2-1 exhaust manifold

[Nanonevol]

Thanks Pete. If anyone else has one off the car it would be interesting to hear what theirs measure. Mine was said to be from a '79 and has 4 bolts. I would think that <.5" X 2 would make a significant difference.

[carl]

i have seen 4-2-1 exhaust manifolds with very noticeable smaller ports at the junction with the downpipe. I don't know what year they were from but assume form the very early 1400 spiders or perhaps the 124 TC sedan. I don't have any so can't offer any measurements. The 4-1 manifold is a very poor design so I think any differences from a 4-2-1 from an 1800 and the 2L would have minimal impact as either one is a vast improvement over the 4-1.

carl

[Nanonevol]

I question the assumption that the smaller ones come from smaller motors. I think you are probably correct that the design of the the 4-2-1 is an improvement itself but I think it may be worth looking for the larger ones. More high school math:

Area of the cross section circle of a 4-1 with diameter of @1.56" = 1.91 sq inch
Area of my smaller 4-2-1 with a diameter of @1.25" X 2 = 2.45 sq inch
Area of larger 4-2-1 with diameter of @1.5" X 2 = 3.53 sq inch
That makes the larger ones @45% larger - I'd say that has to be significant.

[RRoller123]

Increases by the square of the radius.

[Nanonevol]

Yeah my older brother took all the genes for math. He's department head at Providence College.