A great thing about Jay's TGFEIC is cost per page makes it a bargain. There's so much information crammed within that one can spend hours and only go through a few pages.
Something I recently noticed is the performance or more precisely "lack of performance" of the JBA Tri-Y Headers on the 390 Stroker Dyno Mule. At 3,000 rpm the JBAs are clearly deficient lacking a whopping 100(lb-ft) and all of 50-60HP in comparison to all other tested headers. No need to say it, but that is power one will feel behind the wheel on anyones Butt-O-Meter. Surprisingly the JBA headers are right back in the pack on the same 390 Stroker making for impressive Average HP/TQ figures, obviously with such a crappy start they produce impressive power peaks elsewhere that help regain their position on Average HP/TQ. Interestingly the 390 Stroker's missing power is not apparent as said JBA headers are actually performing a few points better then other headers on the 425HP-428CJ Mule at the exact 3,000rpm, the exact point where they went down in flames on the 390 Stroker....Seriously Go-figure?....
It's interesting that Jay tested the 425HP-428CJ Mule down lower (2,500rpm) and sure enough at the low RPM of that scale the JBAs again were lacking some low end grunt, but now were only off by 20 on both HP/TQ not the unheard of 100(lb-ft) and all of 50-60HP of the 390 Stroker at its 3,000rpm start.
Obviously headers work by scavenging and they do so by getting pulses, components, ducks and even voodoo lined up.. I'm wondering on that 390 Stroker equiped with JBAs would it be logical to presume at "part throttle cruising" the Interstate at 3,000rpm would that WOT HP/TQ deficit likely be apparent?................Or could the WOT vs Part Throttle variation alone change power outputs that drastically?..............
