thanks ill prolly end up takin out the cat and muffler and just get aftermarket cheapie exhaust
>>>*Coyote is right, a big exhaust will tend to move the power peak up the rpm scale, while this actually could add peak power the feeling is a loss of low end performance, thus less power.
But the 3.0 does respond to an improved exhaust system, it just needs to be slightly larger and this is one design a dual setup seems to help.
I actually designed and had produced a performance oversize valves line for the engine, I can't say that that was a huge success. There were obvious gains but small, and we did find improvements mostly at the exhaust valve seat exit on the heads. The problem there was the amount of work involved to get to the heads, it is around 10-14 hours to pull and replace them and we were only seeing 2-4% gains.
6 to 10% will make anyone break out in a grin but 2-4% is a bit soft, still noticeable though.
The 3.0 is a big, heavy workhorse design and well cared for we see them run 300K right along, but any tuning upsets or abuse type use and it often is head gaskets time. It was built at a time when fuel economy wasn't a real big concern and that is also an issue in today's world. Still, I read reports of 18-20 and even better, but users are thinking 30+ MPG nowadays. The fuel increase bubble seems to have burst but I doubt we will ever get back to being able to waste the stuff again.
Then the exhaust gas temp on this design reads close to the highest in stock form I have ever noted. High enough it runs normal combustion chamber temps within 75-100? of what I call death territory all the time, with cylinder #5 and #6 being the trouble spots.
The 3.4L 5vzfe is far superior in my opinion. On the 3.0L, we suggest to just rebuild them and send them down the road since the vehicle is usually still sound at normal engine refresh time. Rebuilding maths out to be far cheaper in dollars per mile than replacement of course.
I read reports of a few companies that have had success with cam profile changes. I also played with that myself a few years ago, and mostly found the top end could be improved but not the low end torque curve that everyone really likes when talking about needing more power.
That is because the factory actually back pressured the prototype to improve the bottom end, the ports are a tad too large.
My suggestion is to drive her until she quits, then shoot it and get something different..*LOL**..
BTW: Removing the cat will do nothing, all that might do is finish off some Polar Bears a bit faster, the stock cat is pretty free flowing on these....*Just MHO....*EB
