Atlas Exhaust Header and Silencer

I am assembling a 1968 Atlas which has been apart for many years. The 1-5/8 inch headers I had do not line up well with the silencer on the left side. It is too low and too far out from the frame. Since they have been around my house for 25 years and the source is unknown, I went looking for other options before going down the bending route. I acquired some Andover 1 3/8 headers that do align better. However those have the thick/thin/thick/thin profile. They will not insert far enough into the silencers I have - they hang up somewhere inside about an inch too short. They go in until the front edge of the expanded secton is just about at the silencer mouth.

The question is - any reason not to cut the excess length that extends into the sliencer? It seems to me any length past the fat 1 5/8 section may be superfluous. It is not clear to me yet if shortening the last thin section would solve the problem or if I would need to cut off at the back of the fat section. The related question is, why are they made that long, with that much "extra" in the first place? If necesary for tuning purposes I could perhaps run an expander down into the silencer to get them in but would be concerned about breaking some internal weld.

Anyone run into similar issues?

Hmmm... I recently replaced the unsightly 1-5/8 headers on my 66 Atlas with new 1-3/8 pipes of the same description from Walridge Motors. They went into the factory mufflers without issue. Fit perfectly with no bending. I would measure the distance from the mouth of the silencer to the first obstruction in side using something fattish like a yardstick. Are you using the factory silencer-to-frame mounts? They aren't a complicated mount. Perhaps you could fab up some that give you the extra inch you need.

Perhaps the extra 1-3/8 length is to direct the gasses down the center of the silencer rather than letting them diffuse out into the packing and baffles. As I recall, my 1-5/8 headers were shorter by the length of the extra 1-3/8 bit. I think performance is a little better now but that could be because of the diameter of the pipe rather than how they enter the silencer.