I put a 3" on my 71 cuda 440 with stock manifolds. It all went in fine, but had a horrible drone at 45 mph. I installed their headers, and the drone was gone. It was the easiest exhaust I have ever installed.
I had that exact same experience with my 1970 'Cuda. Manifolds with 2 1/2" pipes, terrible drone. Put TTI headers on, no drone and more power, a winning combination.
Interesting that some kind of sound wave cancellation is going on at highway cruise rpm
when individual cylinders get the added length of their runner down to the 4-into-1 merge, whether 2.5 or 3.0 collector.
https://ttiexhaust.com/Menu_Classics440_Headers.htmhttps://ttiexhaust.com/Classics-Hdr/383440-134/TTI383440-134LS.jpgTTI does not want to say the lengths of the runners so competitors can easily copy.
The runners do not look equal length.
Overall width 41 to 42 inches
Longest runner I guess-ti-mate less than 42 after subtracting collector length.
I wonder if TTI scientifically experimented with varying runner lengths to get rid of part throttle drone in the 60 to 75 mph cruise range,
or was it a “happy accident.”
Sales volume wise having a reputation for “no drone” probably is more valuable than
“more max rpm power gain” than any other header.
Doug’s header design emphasis on “true equal length” would have more chance of sound cancellation just at one relatively narrow rpm and throttle position.
