yeah I talked to Ryan and he basically said it's a long header.
he's using a 5 in. long testpipe and the stock exhaust Bpipe length for his aftermaket exhaust (no cutting) and that there's no way that a cat would fit in there without making some changes to the exhaust Bpipe. You have to get the Bpipe cut and adjusted lengthwise but it's well worth the hassle given the flow improvement for the upper powerband without any low-mid rpm part throttle compromises.
Ryan's running the car in the Honda Challenge H4 class (i.e. road racing) with a testpipe...meaning that if you're mostly daily driving with this header, please use a cat and make the exhaust length adjustments (? SMSP b18b exhaust or have a local muffler shop cut the Bpipe to length on your current exhaust and reweld the flange back on).
This is the first 1.8L b18b hybrid header to my knowledge that is made to work with the b18b i/h/c/e na crowd.
you folks with nonVTEC 1.8L NA have an alternative to the 4-1 vs 4-2-1 dilema now. you don't have to sacrifice one end of the powerband for the other. Something the VTEC guys have long known with all the hybrid headers available for them on the market.
here are some old pics that I had from my hard drive on SMSP header ground clearance and oil pan/tranny clearance shots of the primaries on the 1 piece & 2 piece GSR SMSP header previously posted on the net.
this is what DC4KiD is talking about in the quote above.
I think Dave measures on an actual b18b block and then cuts to size but he can talk about that in more detail better than I can.
The one thing you notice from his designs is how the primaries are lined up in a row and then hugs the pan and tranny as close as possible to get the most ground clearance available. It's a tight precise fit but made to measure exactly like a custom suit made to fit right with no wasted gaps. You'd expect this from a custom header builder compared to a mass produced header...it's like getting a custom made to fit suit from a tailor compared to an off the rack suit from the dept store.