Marge

Well, I just bought a 3.4L engine with all the accessories, ecu, wiring harness. I am going to do a swap into my 3.0L 1991 4x4 longbed DLX. Everything I have read about the swap seems relatively straight forward, except the exhaust. I would like to put the Downey headers on but since they dump down either side of the engine will the passenger side exhaust conflict with the placement of the transfer case and front drive shaft? If anyone who has done this swap on a 4x4 before can tell me how they did their exhaust that would really help me out.
Thanks for any input,
Marge

CoedNaked

I would just run the stock 3.4 exhaust manifolds and take out the 3.4's crossover and have an exhaust shop do a custom crossover over to the drivers side so you don't have to run past the fuel tank, and other lines on the passenger side.

breknraj

I'm in the process of looking into this myself, and I'm wondering if I can use either the 3.4 or the 3.0 Downey headers with the 3.0 Downey crossover, to get the exhaust on the proper side for my 90 SR5 Pickup.

I'm not sure of the differences between the exhaust ports between the 3.4 and the 3.0, and I dont have a 3.4 (yet) to do a comparison. If it is workable, I'd be happy with the Downey 3.0 set up, but I haven't seen any info about this, either.

Getting something fabbed isn't a great option where I am, as I'd have to take the truck about 100 miles to get to a decent place to do it.

Anyone with any thoughts about this?

Marge

Hmm, well once I get the swap completed everything, except the exhaust of course, I think then I will do the measuring and figure out whether I need to use the ORS custom crossover or whether I can do the Downey headers. I know the ORS crossover pipe will work but I would really like to put the headers on.
breknraj:
Where does the Downey crossover go? I am assuming they make it for the 3.4 headers as well.
Thanks,
Marge

hektikwon

I just got a shop to make me a custom cross over and reused the 3.4 manifolds.

rockota

Friend did the swap on a 94 4Runner w/ IFS. Ran the Downey headers w/ a custom crossover below the tranny/above the front driveshaft. An exhaust should should be able to do this for you very quickly.

One note: The Downey headers have a slip fit collector. I've never liked this at all as I find it doesn't seal well. My friend who did this swap had the exhaust shop weld on ball-type flanges before making the crossover. He loves the results.

mt_goat

I'm installing the ORS custom crossover right now:
http://community.webshots.com/photo/...42310107mrSdec

mt_goat

Won't work, the exhaust ports are spaced different. The 3.4 ports are unequally spaced, the 3.0 are not.

mt_goat

Yeah, but like anything made for the stock 3.4 it will crossover to the wrong side. Maybe you could make it work, but why? They just use some crappy slip fit connections that don't seal up very good.

patterson

A shop is doing my 3.4 as we speak, they just custom fabbed some 2.5 crossover.

Marge

Looks like I will be doing the ORS custom crossover then. The Downey headers just seem like too much of a headache for unknown gain.
Thanks guys,
Marge

mt_goat

Some of the guys over on CT use headers but they seem to like TRD headers: http://www.customtacos.com/forum/sho...hlight=headers

Tragic Drive

The ORS crossover is a nice choice and looks to be well made . If ORS made it when I did my swap I would have had the same questions as you.
I went the Downey route and am very happy so far. The ceramic coating on the Headers is really well done and really keeps the under hood temps low.
Not that the temps would be a problem with any of the other solutions to how you decide to pipe the exhaust. Anyways there are a few threads on here regarding exhaust options and cost here's one Link

Marge

Thanks for the info Tragic. I won't be starting the swap for a couple of months. I have to make sure I have all the parts before I start. So I have a while to decide.
Thanks for the information everyone,
Marge

Marge

Well...maybe I will do the Downey headers after all. Check out this thread. The exhaust routing looks pretty straight forward.
https://www.yotatech.com/forums/f130/v6-3-0-header-install-75128/

mt_goat

Well that looks like a mess to me, but the good news is the Downey 3.4 headers are suppost to be better designed and a cleaner install than those 3.0 headers in that write-up. Just make sure you get the ceramic coated ones to keep the heat down and consider welding on flanges after the collector to get rid of the slip fit crap. Also a flex coupling right after each collector would be a good idea.

Marge

Yeah good call on the welding. By "collector" do you mean the end of the header where the lame slip fit is?
Thanks,
Marge

Marge

Mess? Really, I thought it looked okay. The crossover at the transfer case seemed to close though. I would try to have it set back from the transfer by at least 6 or 7 inches so you could at least get the transfer out easily.

mt_goat

Yes, that's where the 3 tubes get collected together as one.

mt_goat

Well I really should clairify that because Chris did a good job of installing and writing it up and I meant no disrespect to him. By "mess" I meant a lot of work involved, and all the plumping going to the EGR valve and other BS emissions crap the 3.0 had.

Also in stock form the exhaust system has shielding to protect lots of wiring, cables, brake lines, fuel lines, etc... that is now up to you to protect someway.

Last summer I was with a group on a trip up to Wheeler lake and one guy who had just installed 3.0 Downey headers had some wires get melted half way up the trail and leave him with a dead engine. After hauling, winching, & towing him off the mountain we later learned the cause.

The problem with leaving more room behind the t-case is the O2 sensor (or in the case of the 5VZFE, 2 sensors) will get pushed back farther from the engine. (the O2 sensor needs to be after the crossover)