Landseer

85 or 86 cats to 16v 84 is bolt up to the existing early manifolds. Caveat, on a couple I've had to put torch to cat downpipes at cat to bend slightly to enhance fit.

If you swap to the 85 86 ss manifolds at same time, though, then you need to fab a spacer.

87 and later cats can also be used, but you need to get creative with transition pipes coming out of cats.

We had a crazy setup on jadz928 s euro 84, using SS manifolds, into 87 cats with a spacer, then a flow master Y, to a big single pipe. Had a spin tech resonator, single in single out also. Beast.

skpyle

You are correct, Wisconsin Joe. My Red Witch is an 86.5, and has the tubular S3 manifolds with the 2-bolt head flanges connected to S4 exhaust. My experience as applicable to this thread was looking at how wide apart the outlet flanges are for the S3 manifolds. Actually, let me make a correction. My cats are gone, replaced by an early Devek H-pipe. It is obvious this pipe has had sections welded together at the head pipes. I can only guess that this was done by Devek.

James Bailey

The 2 valve heads the exhaust ports are not centered but the 4 valve they ARE so when 85-86 manifolds are fitted to the 2 valveheads they do NOT bolt up to the down pipes./ But the twin pipe "dual" exhaust of the Euro S; or 85-early 86 USA is a bolt up to the 2 valve cast manifolds. Worth noting that when Porsche made all the engine changes to get 300 HP they felt it NEEDED the twin pipe exhaust ! If nothing else the twin cat of the 85> has to flow better.