Last year Scott Nelson had Bob Wright port the heads on his 95CI Twin-Cam. He previously had a Stage '?' kit installed at a dealership and the performance was under-whelming.
When Bob was finished he encouraged him to take it to us (Manley Cycle) to have it properly jetted and the ignition timing adjusted for performance. The results are shown below. Unfortunately, I don't have a post Stage '?' kit baseline to compare.
The power peak is around 5300 RPM and we thought that the 'Slash-Cut' mufflers were to blame for the lackluster performance.
I suggested that he change to a pipe that would support a higher RPM power peak. As loud and obnoxious as they are, Thunder-Headers are capable of making power.
I have to admit, at this point, that I don't often get emotionally involved with the bikes I tune, especially Harleys. Since I don't build them, I accept that all I can do is put the fuel/air ratio and the timing right and the rest is in someone else's hands.
In the case of Scott's Twin-Cam I could only look at the charts and make suggestions based on where the power is produced. The obvious conclusion is that the pipe is limiting it.
So, a month and a half later Scott showed up with a Thunder-Header.
The chart is shown below, comparing it with his previous 'slash-cut muffler' iteration. The Blue trace is with the Thunder-header. Looks like it's 'a-horse-apiece'.
Virtually no difference!? You can look at the results with different correction factors or even un-corrected and there are little variations. No matter, the differences are small.
When Bob ported the heads he suggested that Scott put Mike Roland's Andrew's TW11G cams in it, but Scott had been told that the SE 203 cams were the 'way-to-go' and (I think) he didn't want to spend any more on hardware. The 'G' in the designation is for 'gear-drive' which means more $$$$.
I have to hand it to Scott though, he finally had Bob install the cams and brought it back for us to jet and set up the new Screamin' Eagle adjustable ignition.
Below is the final result compared with the Thunder-Header run (DYNORUN.014)
These two runs constitute only a cam change and ignition adjustments, nothing else!