I figure I'll make some flanges out of some heavy stock(1/4" probably). Then lots of little slits and tack welds and test fits. My catalytic converters are shot anyways. I can put an aftermarket one on later. If I modify the factory y-pipe, a standard ball and socket flange set would be easy to put on.
I'm really looking at making the headers to go back to the firewall, down whats left of the factory y-pipe, into a factory Viper X-flow muffler, duals to the back, and then whatever I do back there. Its all in the goal of making the engine work less and use less. Plus I think it'd sound sweet with headers and duals.
I know I'll have time. I'm sure once I tear into the engine I'll find something else I should get and have to order.
Making the flange is the most expensive/ time consuming part. Then, you need to get a kit that's for a 6 cylinder. But, the biggest reason is that headers are supposed to be tuned to make power. You don't just whip a set of pipes together hoping it makes more HP.
Yeah - tuning headers is an art and they can only be tuned for specific RPM ranges. Best bet for efficiency and simplicity is to stick with "log" style exhaust manifolds. Even the 440 HP's used well engineered logs (OEM) and headers didn't add much power to those engines.
If you go with true duals don't go crazy with the tubing size - too big is as bad as too small. Just guessing but I'd say 1-7/8" or 2" would be just about right for the 2.7L. Anything bigger than 2" would most likely be worse than factory.
I have a plasma and the steel stock here for the flanges. I figured it would be easier to make one first and just copy 5 more individual ones instead of making one large flange. I'm not looking at making a lot more power. Its a 2.7.
I don't care about it being tuned perfectly. I'm looking to realistically get a little more mid power out of the car. Some short headers should definitely help with the mid and high range. I'm trying to aid scavenging. I have a few tricks I've picked up to add to them. And I was planning on dual 2 or 2 1/4" pipes to the back.
I"m not new to exhaust. I know the whole theory and have practiced it before.