This is a non-EGR Cat with a triangular flange connection to the matching front pipe. The front pipe had a nice concave end that fits the steel donut. The donut is symmetrical, convex on both sides. The catalytic converter has just a flat flange. I would expect the cat flange to have a concave shape to fit the donut like the front pipe. New Starla front pipe and new Sound cat from Swedish Engineering. Wrong cat, wrong donut or is that the way it is?

One is "wrong", flip a coin... on 240's there are two types of flanges as you've seen: fixed flange and "spin" flange. It's always spin flange to spin flange or flat flange to flat flange. The flat flange uses a gasket, the spin flange, uses the donut.

You can probably get the different types to mate OK for a bit with the donut, but how long it'll stay sealed is anyone's guess. It's basically a right angle on the inside of the flat flange, so the surface area for sealing is almost nonexistent.

If I had a choice, I like the spin flange better.

-Ryan
--

Athens, Ohio
1990 245 DL 133k M47, Cibié E-codes, Now with working wipers!
1991 745 GL 290k (Girlfriend-mobile)
Buckeye Volvo Club

your description sounds right as i recall after doing mine a while ago.
there was as i recall a slight gap after torquing down the 3 bolts between the 2 triangles with the concave piece in between.

makes for a good tight seal. do make sure you tighten evenly. a little on 1 and then move to the other 2 in sequence. otherwise u can tighten the triangles so they complete.... skewed. tighten like you would the lug nuts on the wheel.

Thanks Ted, I hear you. It does not seem right. If the donut is 1/16 inch out of place it will leak because nothing is preventing it from sliding on the cat side and it could throw a code. I'll call Swedish Engineering Monday. In the mean time I'll stop at a few auto part stores and see if they have anything. I think it needs a donut with a flat side to match the cat and a rounded side to fit the flair of the front pipe.

I was disappointed, tools out, car up, and maybe three or four hours of hacking out the old (welded) system and installing the new. I put the car back down.

It looks like the new Volvo cat back system is over the axle, not under like it is now. I have heard of this on older 740s but not 240s. It looks like it will fit, very carefully.

Tom

"I think it needs a donut with a flat side to match the cat and a rounded side to fit the flair of the front pipe."

I agree with your theory, but am not sure if they make a "split donut". It sounds more like the front of the cat pipe doesn't match your header. I think you need a cat pipe like on my 940, where i had to get rid of the rusted "Spin Flanges" (one on each side) and install NAPA versions with a new donut—convex on each side.




--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.