In my spare parts, there seem to be two lengths of header pipe. Considering just two forward parts of a 240 exhaust system:

(a) Header pipe (coming off the manifold) measured from the inside of the upper flange to the inside of the lower flange; and

(b) Cat-muffler section - the distance from the flange in front of the cat to the front face of the muffler - where the front of the muffler is held up by the rubber donuts that are forward of the rear axle.

I needed exhaust systems for 3 cars - from engine manifold to exhaust tip. I laid out the pieces I have around to see what I could weld up. Some new but most used. About 5 systems total and misc extra pieces.

I noticed that there are two distinct systems: (a) header of 30" and (a) header of 32" - Really this varies from 29.75" to 32.5" but the header (a) is hard to measure due to angle and differing pipe sizes. More appropriate to round-off and separate into 2 groups: long and short (a); long & short (b).

As you'd expect, a long Section (a) + a long Section (b) puts the hanger mounts too far behind the donuts; a short Section (a) + short Section (b) puts them too far forward.

Comments.

1. I understand that (a) header pipes vary in bend arc/length so my measurement isn't a true indicator of how far back the header will go. But I balanced 4 of them on the floor - with the long tube vertical & ~level - and the differing lengths are visible and measurable from the floor.

1a. There was no consistent variation between the floating and the fixed 3-hole flange types.

2. Ditto cat tube sections, 1 of which is new.

3. I also get that a custom fab shop could make/buy a header and then make the rest to fit, working front to back. Given that, I'd expect there to be more variation. But with a long header installed, any of the short cat-muffler sections worked; and vice-versa.

Of course I can mix & match by cutting-off / welding-on short sections of pipe to the cat-muffler section (b).. But disassembly of a rusted/clamped pipe from a muffler can be destructive.
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240 drivers / parts cars - JH, Ohio