Superformance headers

[SPF1061]

I am no automotive genius, fer sure....but I have had both of the headers shown in the photo on my Roush 427R. The top ones match up much better with the exhaust ports on the 427R heads and it would seem a no brainer that they would be the best choice. My real world experience is that with headers, as with carburators, bigger is not automatically better. On the dyno, the big headers produced almost exactly (no more) hp up top @ 6000 rpm. We had to richen the jets up several numbers to get this result. The big difference was that they gave up more that 40 to 25 ft /lb torque throughout
the rpm range until well over 5000 rpm, then they equaled out. Seat of the pants. The big headers seemed to wind up faster. They seemed to go from 4000 to 6000 rpm almost instantly. A very nice open unfettered feeling. However, again, down low, they really lacked the seat of the pants instant freight train up yer a$$ feeling of the small headers. At the drag strip, I lost nearly .2 second off my et with the big headers. Bottom line, FOR ME, the smaller headers were the better choice. If you have a really high rpm motor that twists to 7 grand all the time, the big headers would be awesome. If most of your driving is in the under 4000 or so with an occasional charge to 6000, the smaller headers might be a better choice. This is just one guys experience. YMMV. Have fun!
Steve

PS - my headers feed into Stainless Specialties 3" through mufflers - not the stock SPF ones. Just so you know.