The main reason for swapping the cylinders was to move the hot spot closer to the front of the engine in the Gen 3 engines so that they did not need to be reverse cooled. As a byproduct there is also a more positive harmonic signature created when it is used and ABSOLUTELY the header used after the swap makes this shine. If all other parameters are the same between an engine with this cam and another with the original 18436572 order, the revised order engine would not need as much timing at higher rpms and may run slightly leaner. Another positive "byproduct" is the ability to run a few more degrees ignition timing if needed. Most of the gains with this are reliability changes and better thermal characteristics. As always, individual results will vary.
All of this was given to me by a buddy that works in the calibration section in GM powertrain.
I run a 4/7 and 3/2 swap on a bbc. I needed a custom cam ground and Crower suggested I try the swap. I was told the swap takes some of the stress off the number 4 main and relocates that to the number 1 main. I have notice that number 7 hole runs hotter than the rest but that may be unrelated and also the motor doesnt sound like a bbc. Most say it sounds like an LS motor. As far as the hedders go, unless you want to try a tri-y hedder, I havnt seen the benefit, but I am limited to a hedder that will fit in a 69 Camaro with stock frame. I really dont see a performance gain with the swap, just maybe a durability gain. I would like to try an apples to apples comparison with a tunnel ram one one day.
Because when you make that much of a change in the firing order the header tubes are not arranged correctly in the collectors for the correct pulses and you will never see the full benefit of the cam unless you get the headers correct. If you like you can speak with Tim @ Bullet or call Jere Stahl and speak with him about it. Bullet has done testing on this and Stahl made the headers for them.
Thanks Monte442. I've been digging through threads here on the sight and have been noticing people having tuning issues because of the improper header arrangement. Head work and valve-train are in the budget this year, but unfortunately headers are not. I would run the swap cam for a season with these headers for the mere change in cylinder head temp, but don't think I wanna take the risk of loosing out overall. Haven't really ran into a whole lot of info as how the intake design effects the swap though. Thanks, Chris.
Unfortunately I do not think there is an of the shelf header availble to work correctly with that cam.Most people that use that firing order are having headers made as it is mostly for race applications,most don't know about it or those that do won't spend the extra money to get it right.Just so you know,I spoke with Tim from Bullet about that firing order in a BBC and he told me once they spoke to Jere Stahl and got the headers sorted out it was worth almost 50hp. I am sure the rest of the combo has something to do with it,but that gives you an idea what it does power wise and it also makes it run alot smoother down track.