Just curious if anybody knows if a 97 manifold will fit a 99 block/ chassis. Will a 99 downpipe match up
to a 97 manifold? Will a 97 downpipe fit a 99 chassis?
Why is a 97 manifold tubular, but a 99 is cast?

 

97 exhaust manifold will fit fine on a 99+ head. The issue is the flange at the bottom is in a different place.

Basically any 1.8 exhaust manifold will fit any 1.8 engine and chassis, output flange is what you will have to worry about between NA and NB. No clue why a cast manifold was used in 99/00.

 

Youre saying that if somebody used a 97 manifold on a 99 chassis, they'd need a 97 downpipe too in order to connect to the mid pipe?

 

I guess you are talking about the top half of the exhaust manifold. I don't ever split them into 2 pieces because I never get them back together without leaking again.

I have zero idea if the upper half of the exhaust manifold matches the outlet flange placement for both the 94-97 and 99/00 manifolds. It is the lower half with the flange at the mid pipe or cat that does not match on the NB from the NA.

You may be able to swap a 94-97 upper half of exhaust manifold to the lower have of a NB exhaust manifold and it might fit properly. I have never tried that.

 

Also don't forget the EGR fittings won't line up either.