Don't be &quot;That Guy&quot;
Headers are simple. their job is to carry exhaust gases away. there's really no wrong way to make a header. as long as it clears everything, and doesn't leak at the welds, then it'll work.I was thinking about putting a set of headers on my 4.7, but I don't really like the idea of shorty headers. So my idea was to buy a pair of shorties. Cut the collectors off. Weld on some longer tubes with some new collectors on the end and make a pair of long tube headers.
So my Questions are......
Is there any reason this would not work?
Are any of the 4.7 headers made equal length and does it matter?
How do I figure out the correct length to make them?
I also thought about making them stepped or tri-y but that my be getting to complicated.
as far as whether or not equal length primaries matter or not...if your after every last hp that you can get, then yes, it matters, as they all need t obe the same length. but if all you want is a good quality header that flows better than a manifold, then no, it doesn't matter. my truck made 505hp and 535 lbs torque, and my headers are not equal length--they are "whatever it had to be to fit" so while I made good power without equal primaries...I could have probably picked up maybe 3 or 4 HP with equal length primary tubes--maybe even 5Hp. --in my case, not enough to matter. in a high dollar race machine that needs every last .01 in ET...yea, it would matter
now, if you want optimum performance...then you're opening a can of worms there that I don't think you're ready to get into.
your first step would be to determine which RPM you want peak power, which will be largely determined by the rest of your combo--heads, intake, cams, compression, stall on your converter, rear gear ratio, etc.
once you know that, then you need to get on the internet and find some formulas or charts to determine what length and size primary tube will give you peak power at the RPM you want. THEN your next step is to find a way to route all 8 tubes so that they are the same length, and still clear everything.
or, you could just simply fabricate some long tube primaries and whatever they end up as, is what you get...but if that's all you're going to do...then why not just run the stuff that's already available?