3.4 cross over pipe help

mrdoug · 09-22-2009, 03:29 PM

Ok, so exhaust x-over has me a bit stumped at the moment.

I have the 03 motor which has the double walled x-over pipe which is a slightly different design than the earlier ones (I think they switched around mid-02, but could be wrong). The Double walled ones have some sort of rigid insulation in-between the 2 walls that to have a charcoal type consistency.

The earlier ones had 2 pipes (from driver and passenger manifolds) come down to a special flange and on the 'cat side' of the flange collected into one pipe. This newer style collects the 2 sides before the flange. The strange part is the sizes and that's where I'm slightly stumped currently.

Here's some pix to help explain.

First the easy part.. the driver side is fairly simple, 2" OD pipe with a near 90* bend coming out of the manifold:

The passenger side doesn't even look like a real pipe on the outside, but inside is also 2" OD (oddly enough, the weld at flange is welded inside instead of outside, I'll use a 2" hole saw to remove).

You can see above that the driver side joins the passenger side and drop down to this flange, which is 2.75" ID (yes, I'm sure, measured a bunch of times both sober and drunk).

After this flange (before the cat) the pipe narrows down to about 2 3/8":

I've gone ahead and ordered some 2" 180* (4" radius) mandrel bent pipe sections from SpeedWay which I'll cut up for the manifold side. I'll be cutting off the existing flanges to be reused and that part shouldn't be much of an issue.

I'm stumped as to how to collect 2 2" pipes into a 2.75" pipe so that the existing flange down to the cat can be re-used. I've been considering the idea of throwing out these flanges and do something more custom for the drop down to the cat, but can't really find any 2 x 2" -> 2 3/8" collectors.

My next option is go find an exhaust shop to make something for me (but I'm resisting that as I want to do as much of this myself as I can), after that I'm thinking of having to find an older x-over pipe and cat section to cut up and use with this motor.

Any ideas?

As for the double walled insulation part.. I'm not really concerned with it at this point. I'll be ceramic coating inside and out which has had some good reviews (Mt. Goat, and others here on yotatech) and possibly looking at custom heat shields if that isn't enough.

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vital22re · 09-22-2009, 04:14 PM

you could always pickup an earlier style crossover from the 3.4 and chop that up and flip it around. or you could get an exhuast shop to make you a custom one

RobD · 09-22-2009, 06:39 PM

I had a 97 Taco engine that went from the flanges down into two tubes on a common flange. Not enough clearance for the double tube flange, so I ended up just having them cut the flanges off and custom build a crossover so it dropped down on the driver side, into a Y pipe and a one outlet flange. My exhaust diameter is 2 1/2". Any larger than that and you might not have enough back pressure for the engine to run right.

Also, if you're going this route, have a flex joint installed so that the exhaust can expand and contract at a different rate than the engine, otherwise you run the risk of having your crossover develop cracks. Ask me how I know.

mrdoug · 09-23-2009, 08:36 AM

Good tips, thanks.

Actually TC reminded me that I am probably not going to get the other exhaust sections to fit anyways, which means I'm going to be doing a custom exhaust, which means that I don't need to deal with the funky OE collectors, etc.

I knew I was going to be doing custom exhaust all along, I guess I got caught up in making this OE stuff work because I also grabbed the section with the cats and o2 bungs.

I guess I just got too far into the forest and could only see the trees.

RobD · 09-23-2009, 08:50 PM

Yeah, that's the route I had to go. Mine was rusting out, anyhow, and seemed to be the original system.

lbhsbz · 10-11-2009, 12:59 PM

I just finished my exhaust...here's what I did. I had originally planned on using headers so I didn't move the engine forward enough for the crossover to fit. I had to go under the trans.

I used the later double wall manifolds like you have, but I cut the collectors off and rotated them 180° so they pointed where I wanted them. Before I welded them back on, I welded up the "air gap" between the internal and external part of the manifold on each piece, then ground flat and welded back together. I used the flanges off of the original crossover and trashed the rest. I had an old mandrel bent 2 1/4" dual exhaust system off of a chevy truck that I cut up to use the bends. My passenger side stays close to the firewall/floorboard and dumps down behind the clutch fork and follows the bottom of the bellhousing over the drivers side..
My driver's side dumps straight down where it ties into a merge collector and goes into one. It's 3 inches higher than my leaf springs so I think I'll be safe.

I'll try to post some pics later.

A New High · 10-11-2009, 07:49 PM

MRDOUG, funny this comes up right now- I'm inthe exact same situation.

I could take it to an exhaust shop, but it's such a simple piece!

I think I'm gonna get a mandrel 90* for each side- obviously the pass side pointed towards the driver, and the drivers pointed down. Then split the OG pipe that has two small bends to go over the bellhousing, take the inner pipe out, weld it back up, and re-use it to go over the BH.

So from pass to driver it will go: new 90 off pass mani - stock BH pipe - small flex - short straight section spliced into the 90 that comes off the drivers mani and shoots straight down.

In my head- it'll be fairly simple and work great... We'll see how it REALLY turns out!

JonnyBoy · 10-14-2009, 08:37 AM

You're pipe routing might be different, but I was able to use all 3.4 exhaust pieces back to the 2nd O2 sensor. With the crossover reversed, of course, and the exhaust shop had to heat and bend the downpipe so the cat wasn't resting on the tranny x-member. I had the 2 pipe flange, though. I thought I'd seen someone that had cut and reversed the collector piece on your style, though...just can't remember where.

09-22-2009, 04:14 PM	#2 (permalink)
vital22re Registered User Join Date: Feb 2006 Location: kirkland washington Posts: 679	you could always pickup an earlier style crossover from the 3.4 and chop that up and flip it around. or you could get an exhuast shop to make you a custom one __________________ 92 toyota truck 3.4 5spd 4.56 gears magna flow cat and muffler2 1/4 piping isr mod to intake 1.5 bjsfront add a leafs and 2inch lift shackles rear rancho shocks all around sitting on 265/75/r16 nitto terra grapplers

09-22-2009, 06:39 PM	#3 (permalink)
RobD Registered User Join Date: Jun 2006 Location: Calgary, AB Posts: 1,726	I had a 97 Taco engine that went from the flanges down into two tubes on a common flange. Not enough clearance for the double tube flange, so I ended up just having them cut the flanges off and custom build a crossover so it dropped down on the driver side, into a Y pipe and a one outlet flange. My exhaust diameter is 2 1/2". Any larger than that and you might not have enough back pressure for the engine to run right. Also, if you're going this route, have a flex joint installed so that the exhaust can expand and contract at a different rate than the engine, otherwise you run the risk of having your crossover develop cracks. Ask me how I know. __________________ 1991 4Runner, 3.4 5VZFE swap, OME shocks/springs, 33" BFG All Terrain T/A KOs, Pioneer head unit, Infinity speakers, XM Satellite radio

09-23-2009, 08:36 AM	#4 (permalink)
mrdoug Registered User Join Date: Apr 2008 Location: Loveland, CO Posts: 88	Good tips, thanks. Actually TC reminded me that I am probably not going to get the other exhaust sections to fit anyways, which means I'm going to be doing a custom exhaust, which means that I don't need to deal with the funky OE collectors, etc. I knew I was going to be doing custom exhaust all along, I guess I got caught up in making this OE stuff work because I also grabbed the section with the cats and o2 bungs. I guess I just got too far into the forest and could only see the trees. __________________ DD - 02 ext-cab Taco, SAW/AAL lift, Armor a la budbuilt, bentup and badlands, manual hub conversion, 265/75-16 TKO's Project - 85 ext-cab lawn ornament

09-23-2009, 08:50 PM	#5 (permalink)
RobD Registered User Join Date: Jun 2006 Location: Calgary, AB Posts: 1,726	Yeah, that's the route I had to go. Mine was rusting out, anyhow, and seemed to be the original system. __________________ 1991 4Runner, 3.4 5VZFE swap, OME shocks/springs, 33" BFG All Terrain T/A KOs, Pioneer head unit, Infinity speakers, XM Satellite radio

10-11-2009, 12:59 PM	#6 (permalink)
lbhsbz Registered User Join Date: Oct 2007 Posts: 36	I just finished my exhaust...here's what I did. I had originally planned on using headers so I didn't move the engine forward enough for the crossover to fit. I had to go under the trans. I used the later double wall manifolds like you have, but I cut the collectors off and rotated them 180° so they pointed where I wanted them. Before I welded them back on, I welded up the "air gap" between the internal and external part of the manifold on each piece, then ground flat and welded back together. I used the flanges off of the original crossover and trashed the rest. I had an old mandrel bent 2 1/4" dual exhaust system off of a chevy truck that I cut up to use the bends. My passenger side stays close to the firewall/floorboard and dumps down behind the clutch fork and follows the bottom of the bellhousing over the drivers side.. My driver's side dumps straight down where it ties into a merge collector and goes into one. It's 3 inches higher than my leaf springs so I think I'll be safe. I'll try to post some pics later. Last edited by lbhsbz; 10-11-2009 at 05:08 PM.

10-11-2009, 07:49 PM	#7 (permalink)
A New High Registered User Join Date: Jul 2008 Location: Gresham, Oregon Posts: 35	MRDOUG, funny this comes up right now- I'm inthe exact same situation. I could take it to an exhaust shop, but it's such a simple piece! I think I'm gonna get a mandrel 90* for each side- obviously the pass side pointed towards the driver, and the drivers pointed down. Then split the OG pipe that has two small bends to go over the bellhousing, take the inner pipe out, weld it back up, and re-use it to go over the BH. So from pass to driver it will go: new 90 off pass mani - stock BH pipe - small flex - short straight section spliced into the 90 that comes off the drivers mani and shoots straight down. In my head- it'll be fairly simple and work great... We'll see how it REALLY turns out! __________________ Tyler 1992 White Runner 3VZ/A340 5VZ/R150(in progress)\|Inchworm 23spl\|MC XD 23spl 4.7's\|D60/14B waiting to go in after winter It's A Jaap Thing

10-14-2009, 08:37 AM	#8 (permalink)
JonnyBoy Registered User Join Date: Apr 2007 Location: Lone Pine, CA Posts: 409	You're pipe routing might be different, but I was able to use all 3.4 exhaust pieces back to the 2nd O2 sensor. With the crossover reversed, of course, and the exhaust shop had to heat and bend the downpipe so the cat wasn't resting on the tranny x-member. I had the 2 pipe flange, though. I thought I'd seen someone that had cut and reversed the collector piece on your style, though...just can't remember where. __________________ Jonny 1990 3.4 5spd 4Runner, 33" BFG KM2's 1983 5spd Shortbed, 35" BFG M/T's with no lift! Soon to be...who knows, but the 35's ain't stayin! "If at first you don't succeed, skydiving's not for you." -Unknown

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