Running a Bw s480. It’s 5” I’m necking down to 4” I’m curious if anyone else has ran a single 4” all the way out the back. It really curious about 4” between the heater box and engine. Non Ac

 

Good luck! I had a 3" in the same spot and it was very tight.

 

When I ran a single 4" down pipe I modified the heater box and had plenty of room. It can be done.

 

I did the same thing, ran the downpipe angled straight downward parallel with the box after I made the cut . It barely kissed the number eight primary, but it did clear. Could have made more room by redoing/rerouting the eighth primary on the header, but I wound up switching back to a three inch downpipe because the four inch was overkill....

- Rob