I recently bought the Calmini headers for my sidekick and found that the instructions say they're for a 1.6L, and my sidekick is a 98, which has the 1.8. The description where I bought it from was unclear in this and when I tried to take my exhaust stuff in to get installed, they said they couldn't put the header on. Are the 1.6 and 1.8 different?

Yes they are slightly different. But the reason Iv gathered for there not being headers for the 1.8 is because the stock manifold is pretty much the same thing as a header.

Ok perfect. Looks like I'll be returning this thing then. Thanks a lot.

Isn't there a company out of Australia that makes headers for the 1.8l and 2.0l motors?

There is a header made in Australia for the J20, that will fit the J18.  There are a few things to consider before buying it.  You have to add your own EGR tube and the hanger bracket from the catalytic converter needs to be removed.  I would also suggest that a section of flex-pipe is added between the header outlet and the catalytic converter.

Here are pictures from my J18 install.

Edit:  Well I just replied to an ancient post.  No activity here since the reboot?

So the stock exhaust manifold on the 1.8 engine was made out of cast metal?   The J20 is made of  tubing.

The Sports had a cast manifold that cracked easily.  If you zoom in, you can see cracks at nearly every place a runner meets another runner and some are perpendicular to the runner.