rkutzner wrote on 12/31/69 at 16:00:04:The pipe might be cooler from the outside to the touch because of the wrap, but the header wrap keeps the exhaust temps HIGHER inside the pipe. This aids in scavenging the exhaust out of the pipe, in effect making it flow better. This is a common drag race thing, I did it on my Z400, too, for a while but it didn't add any noticable performance. I'd like to see the pics, though, as it will make it look bad !!! 8)
Not to cast a shadow on the idea - but the biggest reason we did it and with zeal I might add at the track was to get the heat out of the engine compartment, the ambient air around the intake would drop as much as 50 deg f - cooler intake air is denser air so you can cram more fuel in with the same air volume.