Lankan

Been reading a lot about how bad the design of the exhaust manifolds are on the 3VZE (blowing HG's and robbing power). For those of us out in CA, passing smog is of importance (visual inspection and the test itself). My understanding is that if you install headers, you will also have to lose the EGR and the PAIR valve...right? Has anyone tried the following:

1) Cut the stock passenger side manifold where the first bend is (where it starts to wrap around the passenger side rear of the engine).
2) Also cut/remove where this pipe meets the driver side and seal it with a plate.
3) Have an exhaust shop run the appropriate diameter pipe from the passenger side bank towards the bottom of the truck.
4) Modify area (before CAT) with a "Y" pipe and connect the new pipe coming from the passenger side cylinder bank.
5) I'm thinking to keep the stock CAT and replace the stock muffler with a high flow, 2.25" (as that's the stock size anyway).

Wouldn't this drastically improve exhaust flow, and increase power in the process? I'm assuming this would also still be smog legal as well as they won't be able to see it during the visual inspection. Been thinking about this for a few days and just wanted to get you guy's opinion!

4x44runner

As a matter of fact you just named a mod! Crossover elimination! Search is your friend! But yes it is done. Im almost done with mine! Although my motor is out..

Wrenchinjoe

You can reuse the existing crossover flanges. The driver's side flange can be sealed off and made into a block off plate. The passenger side flange can be rotated to bend downward rather than around the back of the engine, so leave enough crossover pipe to save the bend.

Also, not all headers require losing the EGR and PAIR systems. Thorley headers have connections for those and are smog legal in CA.

Lankan

The best price I've seen someone get on the Thorley headers is $540 shipped. Lets say it will be close to $600 by the time you get it installed. I'm thinking the process I described can be done between $200-$250?? And the results (increased exhaust flow & power gain) may be about 80-90% I would think if you compared it to the Thorley header. My numbers are all assumption, was just trying to think of a more cost effective way to increase the exhaust flow.

Lankan

4x44runner, thanks for the name of the mod that I was describing "crossover elimination". Been reading since you posted that up... and now it's obvious to me that many have done it. Has anyone mass produced this and started selling them as a bolt-on? Also, has anyone done dyno testing to compare stock set-up vs. crossover elimination vs. Thorley (similar) header?? What I'm mostly looking for is for the truck to be a bit more responsive, and be able to comfortably maintain freeway speeds (70mph) even if there is high head winds or an incline. I hate having to floor it and rev it to 4k rpm to maintain 60mph under the conditions mentioned. I also don't want to hear too much of an exhaust note (hum) while on the freeway either, so may keep the stock CAT and muffler, however if needed, I may change the stock muffler to a 2.25 borla offset style muffler.

donomite49

i have done the crossover mod on my 3.4 swap.
i'm running obx (like thorley's design) headers and fabbed up my own crossover that runs underneath and joins right in front of the precat o2 sensor before joining the original exhaust with a flange at three points for access.
you can use the same idea for the 3.0.
i did not want the crossover on top of the engine where it is a pita to get to. i used stainless steel fittings and pipe from jeg's and tig welded. i don't know, but it should be smog legal in cali, as i have been through the strict cali smog check program when i lived out there. research before you jump on this mod.
you can see a short vid on the link in my sig.