V6  3.0 Header Install
2/14/2003

But take my word for it when I say that if you know how to turn a wrench, you can install these headers.  I ordered the ceramic coated headers from Downey Off Road, which came with everything needed to install them.
The reason I chose ceramic coating is because it lasts twice as long, maintains the cerma-chrome look, and is supposed to move heat better than regular headers.  To me, the extra cost for the ceramic coating is definitely worth it and they have held up wonderfully so far.

Scott Wilson did an excellent write-up on this install and I pretty much used his instructions.  But I also ran into a few dead ends as far as his instructions go concerning the reed and EGR valves.
And the instructions Downey sent with the headers were a little confusing to me, especially when it gets to the technical stuff such as these valves.  Needless to say, I completed the installation almost 100% to Downey’s specifications.

With this article, I'll try to explain how I did it as simply as I can so if any of you beginner wrench heads out there try this install, it'll make it a little bit easier.  Although it's always nice to have a guy you can call to fix anything you happen to mess up like I did.
Another thing to keep in mind is that I have a standard transmission, so those of you with the automatic are going to have to follow some extra steps included in the instructions from Downey but not mentioned in this article.

First off, it's good to have a lot of tools on hand, metric of course.  A MUST would be some deep or medium depth sockets for a ratcheting wrench, a good selection of open and closed ended wrenches, an adjustable wrench, a hacksaw, and some good rust penetrant (I used PB Penetrant) along with some copper coat gasket sealer.

The tool that I found most useful was a breaker bar that had a swivel head that sockets could be attached to, which allowed good access to the exhaust manifolds.
I only used this tool for loosening the nuts attached to the studs in the cylinder head so I could remove the manifolds.  I could not get the nuts loose with a regular ratchet.  A socket with a swivel head or a longer handle to provide more torque would also be sufficient.
Scott Wilson's install suggested the use of an S-wrench, but I do not know what he was talking about because I could not find one anywhere.  I managed to do without it.  Lastly, one mandatory backup tool:  a Sawzall or any kind of pipe cutting tool.  I could not have completed my installation without it.

I started off by prepping my engine.  Disconnect the negative cable to the battery (I always do this when working on my engine), take apart the air hose assembly from the air box to the throttle body by loosening the clamps and pulling it off, and remove the spark plug wires.
I didn't let my engine cool down enough before working on it and pulled the connector out of one of the wires.
Call it anxiety, but make sure your engine has cooled for at least 30 minutes to an hour before you work on it.  Also, it's a good idea to draw a map as to which plug wires go to which plug so you won't forget when you're done with the install.

I didn't find the need to remove the air box, battery, or vacuum hoses that clutter up much of the passengers side of the engine.  In my opinion, the battery and air box didn't even get in the way and I really didn't feel like messing with the hoses so I worked around them.  If you remove them, draw yourself another map so you'll know where they go.
As my last preparation step, I sprayed down every nut and bolt I could reach or see with the penetrant.

First, I worked underneath the truck, unbolting everything attached to the exhaust pipe all the way back to the muffler.  This includes the catalytic converter and the 02 sensor.  I also removed the exhaust pipe mounting hardware that was screwed into the transmission.
With all this gone, the only thing that should be left are the manifolds and the crossover pipe.  I started with the drivers side manifold and crossover pipe.
From underneath the truck, I unbolted the bottom two bolts that connected the pipe to the manifold with ease.  Then I moved under the hood to work on the last bolt on top of the pipe.  I worked on this bolt for what seemed like an hour and no matter how hard I pulled or how much penetrant I used, the thing would not budge and I eventually took the sides off of it.

This is where the Sawzall came into play.  I sliced through the pipe as close as possible to the manifold in a matter of minutes.  If I had to do it again, I'd work with the top nut first, because maybe the removal of the bottom two first is what caused it to bind.  With the drivers side manifold free, I unbolted the 6 nuts from the studs using the breaker bar to loosen, then a ratchet to finish.
Then I slid the manifold and gasket off the studs and used the 2 nuts Downey supplied with the headers, jam locked them onto the studs, and extracted those too.  After this, the head should be fully visible.

After all that work and I knew the passenger side would be even harder, I let my anxiety get to me and went ahead and installed the drivers side header.  At the time, I knew NOTHING about how a header should be installed and I paid the price.  I sprayed Coppercoat on both sides of the gasket, then installed the top two bolts on the left and right side to hold the header in place, then installed the rest.  BIG MISTAKE.  Toyota cylinder heads are made out of aluminum, which requires special care when screwing into them.

I didn't know it at the time and stripped the threads in a hole or two on the drivers side and at least 3 holes on the passenger side when I finished installing it.  I later learned the proper way to do it would be thread all the bolts in even intervals.  This is especially easy if you have a friend to hold the header in place while you do the threading.  Tighten them all at even intervals gives you the best chance of preventing the thread stripping I went through.
A good rule of the thumb, if the bolt doesn't look straight going into the hole, it's probably isn't!  If there's too much resistance before the bolt gets all the way in, back it out and start over.  Take your time when doing this because a little patience is a lot better than paying the $350 I had to pay to completely fix the holes I stripped.  You might find it more beneficial if you take the tires off and try to work through the wheel well so you'll be able to see if it's lined up.  Here is a picture of the drivers side header installed.

Alright, back to the install.
I took one look at the crossover pipe connected to the passengers side manifold and knew there was no way I could get to the bolts through the top (since I had chosen not to remove any vacuum tubes or hoses), and I spent about 30 minutes trying to find a good angle to at least ONE bolt from underneath, only to be disappointed in my efforts.
For me, there was only one solution:  Sawzall again.  I snaked the saw up to the pipe, got a good angle, and began hacking.  I couldn't get all the way through but I got pretty close.
If you've removed your sway bar, you probably won't have any trouble.  After looking hard enough I figured I'd be able to get it all the way through if I loosened the manifold and lowered it off the studs a little.  So I went back up top and started working on the manifold.  I unbolted the EGR and Reed valve tubes that connected to the manifold (I used an adjustable wrench) and tossed them aside; keep the Reed Valve tube because you'll need the compression nut for later.  This side is a lot harder to reach all the nuts than the drivers side due to all the cluttered EFI junk and whatnot that snakes around it.
After a lot of experimenting with different angles, I finally got every nut off.  I slid the manifold down a little then went back underneath and proceeded to hack through the rest of the crossover pipe.  The saw barely made it through. I slid the manifold completely off the studs and removed it.
I then found that the crossover pipe came out with no problem by pulling towards the passenger side from underneath the truck.  I didn't even have to lower the transmission and I'm pretty sure this was because I had hacked off the flanges that were still attached to the manifolds. Using the Sawzall was the only time I didn't follow Downey’s instructions.

My next step was to install the header, which I did wrong and paid for it later.  But as for you guys, follow the steps above and you should be fine.  I didn't find the need to trim the flange on the header because it fit right up but if yours happens to conflict with the steering pump, trim it a little with an angle grinder.
If you haven't noticed from the pictures, I used some of the stock manifold studs to mount the passengers side of the header.  The only reason I did this is because I messed up some of Downey’s bolts on my first try.  The studs have worked fine for me so which method you choose is up to you.  Here's a picture of the passenger side header installed.

This is where I ran into the dead end with Scott Wilson's installation instructions.  He fashioned his own custom EGR and Reed valve plumbing, which I did not want to attempt since I know nobody who could fabricate such a thing.  Downey’s instructions confused me, but this is where my mechanic friend helped me out.
The Reed Valve is the one located closest to the firewall or cab of the truck and the EGR valve is the one located closest to the radiator or front of the truck.

Having cleared that up, the EGR valve plumbing mounts to the header with the supplied steel flex pipe with a little bending and fitting but basically no problem.  But save this step for last so you will have room to work with the Reed Valve.  Remove the EGR if you need more room to work with.  Unbolt the Reed Valve from the engine by unscrewing two bolts out of the mounting flange and removing the hose that also connects it to the engine.  The valve will not mount atop the copper pipe unless you trim the flange off.  This is easily done with a hacksaw so I removed a good bit of the flange.
The only downside of this part of the installation is once you cut the flange, there's no going back because the Reed Valve will not mount back onto the engine.  But hey, it's worth it, right?   While you have the hacksaw, cut off the original compression nut (this is the nut that screws into the reed valve itself) from the tube it came on.  Press the flared end of the copper pipe onto the reed valve, and slide the compression nut on, then tighten.  Then slide the crush nut, followed by the crush sleeve (which looks like a ring) onto the bottom part of the pipe.  Sit the pipe onto the mounting location of the header and make sure it fits with no interference from the mounting flange of the reed valve.  Seat it on the header firmly and tighten the crush nut.  It is important to do this right the first time to form a good seal.  This is the only part of the installation that was not included in Downey’s instructions at all, but I found to be necessary.  The tube that connects the Reed Valve to the engine will no longer reach the valve because of the new mounting position.
You will need to purchase more rubber tubing the same size and cut it a longer length so it'll fit.  I happened to have some lying around so I used it and it hasn't given me any problems.  Here is a picture of the Reed Valve.

Replace the EGR valve if you removed it while working on the Reed Valve, run the steel flex pipe to the mounting position on the header, and tighten.  Make sure you bend the brake lines to prevent any interference with bottom part of the header.  Here's the EGR installed.

Congratulations, that's the last step and you've just installed your V6 headers.
Reconnect everything you took off to do your work and get a new exhaust system made.  Downey sells all the pipes to run the exhaust to the catalytic converter, but I'm not too fond of the way they use clamps to attach them, and got an exhaust shop to create my own custom exhaust system, including the crossover.  It cost me $200, which I think is the same price as the pipes from Downey.  Not to mention, the shop did a really good job on the bending to fit perfectly around the transfer case.  The following picture illustrates the custom crossover.

I chose to use 2.25” pipe right off the headers, then after the crossover I bumped it up to 2.5 the rest of the way out.  The reason for using the smaller diameter pipe off the header was to create some back pressure for more low end torque.  I might try bumping it up to 2.5 one day just for curiosity purposes, but for now it works great.
As you can see in the picture, I had the exhaust shop cut out the 02 sensor mounting flange and weld it into the 2.5” pipe after the crossover.

This is not a big deal for an exhaust shop to do, and if yours gives you trouble for it, go somewhere else.  It's a necessary step to getting optimal flow.  When I first had the system made, I left the catalytic converter off, which turned out to be a big mistake.  Some people will say your truck doesn't need a catalytic converter to run right.  Well then maybe they can explain why my idle kept fluctuating up and down with it off.

After talking to a more experienced shop, I popped for a free flow converter with a 2.5” inlet and outlet.  I noticed the difference right when I left the shop.  I had more low end torque and a punchier throttle due to the restored back pressure.  Amazingly enough, my high end horsepower didn't seem affected at all.  The tailpipe is just a simple 2.25” pipe that stops short of the spare tire, so mud won't clog it up when on the trail.  I wanted a turndown, but it would have sounded too loud with my 40 series Flowmaster.

I definitely notice more torque and horsepower than before, and hopefully I can back it up with a few dyno runs in the near future.  If I do, I'll be sure to post them.  By far this has been my best performance mod to my engine to date.  In light of my troubles with stripping the stud hole threads, I would recommend anyone installing the headers to leave the studs in and to try to mount the headers on them instead of using the bolts Downey supplies.
I don't know if this can actually be done or not, but if one of you actually try it, be sure to post your results.
Helicoiling is also an option and provides much more strength to hold the studs in place.  Another option recommended from Tim at DOA is to use GM rocker arm studs, which are slightly bigger (7/16”) than the regular studs on the end that goes into the head, allowing for an easy repair to stripped holes.  I will probably use the GM studs to replace all of my bolts later on when the rig retires as a daily driver.

Downey’s Instructions:
1. Loosen Clamp and remove air cleaner duct from throttle body on engine. Unplug electrical cord from flow meter on top of air cleaner. Remove three air cleaner mounting bolts from inner fender panel. Remove air cleaner assembly from vehicle.

2. Remove 3 spark plug cords from drivers side spark plugs and tie or tape them out of your working area.

3. Remove the outer heat shield from the left side exhaust manifold.

4. Unbolt and remove the Oxygen Sensor from the stock tail pipe (in front of the catalytic converter).

5. Remove the tail pipe between the left side exhaust manifold and catalytic converter.

6. Unbolt the cross-over pipe (behind engine block) from the left side exhaust manifold.

7. Unbolt left side exhaust manifold from engine.

8. Remove left side exhaust manifold, then remove the 6 mounting studs. Using two 10mm nuts included with the headers, jam lock them together on each stud. The studs can then be removed by wrench.

9. Unbolt cross-over pipe from right side exhaust manifold. Remove cross-over pipe by pulling it toward left side of vehicle. Remove cross-over pipe by pulling it toward left side of vehicle. If the cross-over pipe binds between the engine and fire wall preventing removal, it will be necessary to put a jack under the transfer case cross member, unbolt the cross member from the frame, and lower the transfer case approximately 1.5 inches. After removing the cross-over pipe from the vehicle, remount the transfer case cross member.

10. Spray Coppercoat (or equivalent gasket adhesive) onto both sides of the left side header gasket. Install the left side header and gasket onto the engine using them 10mm bolts supplied.

11. Before removing right side exhaust manifold:
a. Remove spark plug cords from spark plugs and tie or tape them out of your working area.
b. You may find it necessary to remove the power steering hose from the side of the reservoir and tie or tape it out of your working area. WARNING - If you lose fluid, do not forget to refill the reservoir before operating the vehicle.
c. Remove EGR valve and Air Suction Reed Valve from engine and exhaust manifold. Note - Some non California vehicles do not have these valves.

12. Remove right side exhaust manifold, and then remove 6 mounting studs as described in step #8.

13. Before installing right side header, bend coiled brake lines and fuel line closer to right side of frame, wire tie fuel line to brake lines to insure adequate clearance from header.  Use wire tires to insure all electrical and plumbing have adequate header clearance.
AUTOMATIC TRANSMISSION ONLY - Disconnect automatic transmission kick down cable from throttle body and engine mount clamp. Reroute cable straight up firewall (vertically, away from header), the reconnect to clamp and throttle body.
AUTOMATIC TRANSMISSION MODELS - Your transfer case has an oil cooler mounted to the right side frame beside the transmission. Remount the cooler slightly reward (in front of the transfer case) or remove both oil cooler hoses, remove cooler from frame, remount cooler to floor board behind transfer case using Downey hose kit #DOW32910. WARNING - You will probably loose some fluid during this procedure. Do not forget to refill the transfer case before operating vehicle.
AUTOMATIC TRANSMISSION MODELS - It will be necessary to bend the transmission tube that carries fluid from the transmission to the front cooler inward toward transmission. Bend it inward far enough to clear header, but not far enough to interfere with the transmission shift linkage.

14. Attempt to loosely mount the right side header to ensure there is adequate clearance (no interference) between front end of header flange and power steering pump. Trim if necessary!

15. Spray Coppercoat (or equivalent) onto both sides of the header gasket. Install the right side header and gasket onto the engine using the 10mm bolts supplied.

16. MOUNTING REED VALVE - Remove the original plumbing from the bottom of the reed valve. The 2 bolt aluminum mounting flange on the reed valve can be removed with a hack saw (optional), since the reed valve will no longer remount onto the cylinder head often it is mounted onto the header plumbing. Cut the original plumbing to remove the original compression nut that screws up into the bottom of the reed valve. Slide original compression nut onto copper tubing toward the flared end. Screw original compression nut and crush sleeve onto opposite end of copper tubing. Position copper tubing down into rear fitting on header and screw crush nut onto header fitting. WARNING - When tightening crush nut, ensure that copper tubing is tightly pressed into header fitting and fully seated. If not, the crush sleeve will not crimp the copper tubing and form a seal. After completing installation of the reed valve, ensure that rear spark plug wire does not come into contact with the copper tube. Tie back if necessary.

17. MOUNTING EGR VALVE - Remove original plumbing from bottom of EGR valve. Position EGR valve back into its original mounting position on the engine, do not tighten. Hold stainless flex tube (supplied with headers) up to fitting on EGR valve and front fitting on header. Determine exact length flex tubing should be when fully seated into the header and EGR valve, trim tubing to proper length. Position crush nut and crush sleeve onto one end of the flex tubing. Fully seat flex tubing into front fitting on header and tighten crush nut finger tight. Cut original plumbing to remove original crush nut. Install original crush nut and crush sleeve onto top end of flex tubing. Fully seat EGR valve down into flex tubing and tighten crush nut finger tight. Before fully tightening crush nuts, position EGR valve back into its original mounting location and tighten original mounting nuts. After determining flex tubing is still fully seated at both ends, fully tighten crush nuts.

18. Reconnect spark plug cords, both sides.

19. Reconnect power steering hose to reservoir if disconnected earlier. Check fluid level.

20. Reinstall air cleaner assembly.

21. Connect new tail pipes to new exhaust system.

22. Install Oxygen Sensor into the fitting on the new exhaust system.

If you choose to do this mod good luck and if you have any questions  (Churnd) on the Yotatech Forum.

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