Snorkeldepth

How's that for a specific title? It's either got to go under, over or around the back right? What should I do? I think I'm going to stick with 2" for the crossover and go to 2 1/4" from the cat back. I'm very open to ideas. Pictures of what you've done would be great! I've seen the photo of the "around the back" configuration that Churnd did. I couldn't figure out how the Thorley/Jardine "Y pipe" routs. The Downey crossover is an "over" configuration right?

Oh, it's a Jasper 3VZE with an ISR pushing 4.88s and 33 x 10.5s. I currently have a Jardine 2 1/4 catback and a Magnaflow cat (bolt in replacement).

snap-on

NWOR is around the back. (i have it on my truck)

I have downey headers that are going on my rebuilt motor this weekend and will have to come up with something myself. (for my 4runner)

I have an auto and will have to relocate the transfercase cooler. but plan on routing behind like the NWOR design .

Ill likely go with 2.5" after the Y pipe like on my truck. what are the downey headers? 2" ? i havent measured...

Snorkeldepth

Hmmmm . . . . I thought it was 2" but I just measured the ID with my Stanley tape measure and it looks like about a sixteenth over 2 1/4". I remember reading that 2" down to the Y would preserve low end torque. I wonder if 2 1/4" all the way would be good.

snap-on

i wanted to say that if you bought downey's Y pipe it (obiously) mates with the headers (which i thought were 2.25) and after they meet it exits at 2.5"

Snorkeldepth

Thanks Snap-on. It has been said in other threads to avoid the Downey crossover and go with a custom crossover. I don't know if that means to have a custom crossover that's routed like the Downey crossover or use some other "under" or "behind" routing. I figure if I'm going to pay someone to do some custom work I might as well do it right. Is there a right way?

Snorkeldepth

I checked the Downey catalog again. Their crossover is 2" pipes merging into a 2 1/2" pipe that connects to the rest of the exhaust.

Snorkeldepth

Does anybody else have any input whether over, under, or behind is the better way to go?

AH64ID

The advantage to the "over" design is that you have stock heat shielding there, on the same note, going around back you have fuel and brake lines on the pass side. I think if someone makes an over pipe I would use that, espically if one were to be ceramic coated.

ChickenLover

I have the downey cross over. It's of good quality. However, it sits pretty damn close to the tranny pan. I've been running it for years without an A/T oil light coming on. But that extra heat can't be good for the ol' gears.

AH64ID

It looks like noone makes a header/crossover for the stock location then?? Does downey offer that part with ceramic coating?

If thats the best I think I would route around the xfer case so I didnt loose ground clerance..

ChickenLover

The location of the stock crossover is the reason most people switch to headers in the first place. The oem cross-over is a very bad design (very restrictive). It's been known to bend valves (namely on the #5 and #6 cylinders). It was a money saver for toyota because it allowed the driver's side components to be put on either side of the truck (European market).

To the best of my knowledge, Downey does not offer a ceramic coating for their cross-over.

Ground clearance is a non-issue with the downey cross-over. It sits about even with the crossmember.

Snorkeldepth

In your photo do I see correctly your torsion bar, the crossover, and then the crossmember going from left to right? If that's the case it looks like I might have a problem with the BB crossmember/skidplate. Maybe the around the transfer case would work best for me. Is the "behind" routing good from a gas flow characteristics perspective?

ChickenLover

Yeah, left = front of truck. Can't help you with behind routing and gas flow characteristics.

Snorkeldepth

Thanks guys! I'm a little concerned with heat on the passenger side and all the stuff Nala mentioned is tucked there. I wonder if anyone has had heat related issues using the "behind" routing method.

ChickenLover

Crossover talk aside for a second. With downey's headers you will more than likely have heat issues with the headers themselves. The passenger side header comes VERY close to the floor board. So close in fact, it has actually burned a hole in my carpet and melted my floormat (and I have the ceramic coat). You might want to consider a custom bend or a heat rap before you put 'em on. Also, make sure to route all of your cables/hoses etc away from those bad boys. They get waaay hotter than your oem manifolds. Anything that is close to those headers will burn up. You should see what happened to my tranny kick down cable.

Snorkeldepth

Yeah CL I remember you mentioned those heat problems. That prompted me to do the 1" BL. I was thinking of upgrading the heat shield mat on the firewall. I saw some double sided stuff that I was thinking of installing over a wider area of the firewall than the stock heat mat. I have the ceramic headers too. Did you have anything else damaged from the heat? I hope we hear from the guys who have done the "behind" routing.

jp123

Heat hasn't been an issue for me. I've been running the Downey headers, crossover, and full exhaust for over a year now with no problems except for having to replace a C-clamp on the header. (Wish the headers had better connectors for the piping with the premium price they charge!)

My preventative steps to avoid heat damage was to buy some high temp tape from the hardware store and wrap it around some close electrical wires and brake lines (You must bend the brake lines slightly for clearance). I also used heavy duty zip ties that have held up suprisingly well.

The headers DO come very close to the passenger side firewall and floor board. My solution was to use the factory heat insulation that was in place behind the stock crossover pipe behind the engine. The headers sit so close to the firewall that I only needed to wedge the insulation to keep it in place, although I did zip tie the insulation to some points I found away from the heat. The insulation actually touches & sits on top of the header!!! I bet on the fact that it wouldn't burn & seemed to have held up fine, other than some singed edges.

Conclusions:
(1) I wish I bought the ceramic coated headers, cause mine look pretty discolored.
(2) The crossover pipe fits really well.
(3) The full exhaust needed to be trimmed quite a lot & has already started to rust!!! (Too many snow trips I guess.)

midiwall

I'm on a 3.4, but fwiw, I went under with the crossover on my Downey's.

If you choose this route, be sure to make the crossover removeable otherwise you'll come up with all sorts of new words if you ever have to get to the tranny pan. The shop that did mine got to do it twice once I pointed that out.

snap-on

so i guess if you go under like this, then you DONT have to relcate the transfer case cooler?

I really like my NWOR behid design and planed on duplicating it for the downey setup. My NWOR headers come VERY close to the DRIVERS side floar board. enough were when they were installed there was some insulation stuffed between them and the firewall and just held there by friction. My feet get a little warm on road trips but it has caused no problems with carpet or any kind of wireing/cableing in the 6 or so years ive had it.

Ill look at getting some heat tape for the pass side before i put them in.

AH64ID

With a 1" BL there might be more clerance for the behind route. It looks like the downey header is too long for a over crossover anyways. With a BL there also would have been more room in the stock location, but then there is the valve problem, I am guessing they get too hot??

I dont have my truck with me, so I can remember how much room is between the xcase and the fuel tank, and it different for each wb, but.. the behind idea doesnt sound bad, even having to move the xcase cooler. A little strategic heat shielding a done....

makes me glad I am a 22REguy

Also saw this a while back....I want to use it where my exhaust routs close to my bed, get warm on long hauls, espically when I have coolers there trying to keep my BEER cold for camping....

http://www.flowmastermufflers.com/pr...pe+heat+shield