Installing Downey 3.0L V6 Headers

Http:// Short Cuts
Author: Scott Wilson December 1999
No job is too tough!

This article will walk you through the installation of Downey's V6 headers. I know for many of you the thought of installing your own headers is downright scary. Trust me on this one, any do-it-yourselfer can do this installation, you don't need to be a trained mechanic.

It's definitely worth mentioning that this installation will be SIGNIFICANTLY easier if your truck or 4Runner has a body lift on it. My 4Runner has a 2" body lift. Much of the work can actually be done through the gap between the frame and body if you have a body lift.

This installation can be done with tools that most people have in their garage, however I feel that a 17mm S-shaped wrench should be on the required tools list for this job.


Clear space to work

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.

To begin I chose not only to prepare the drivers side, but the passenger side as well. I completely removed my spark plug wires, to ensure they'd be out of my way. On the passenger side I also removed the battery, and many of the vacuum lines that would otherwise be in the way. BE SURE to draw yourself a map as to which vacuum lines go to which connectors, as by the end of this installation there is no chance you would remember.

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.

Stock components removed

This is your goal as far as disassembly. You want to have both exhaust manifolds, and the crossover removed. None of these part will be used again, so do not feel the need to be gentle with them.

Remove studs from engine block

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.

Driver side

I was surprised to find that nearly every bolt came off with ease, after being soaked in Liquid Wrench for awhile. One of the bolts that held the cross-over to the drivers side manifold was a huge problem for me. I worked at it a long time, and only proceeded to take the sides off the nut. Then I remembered that there is no need for the cross-over once the new exhaust is installed. I used a reciprocating saw, and sliced through the stock crossover in a matter of seconds.

The cross-over itself came out from between the engine and firewall very easily for me because of my 2" body lift. I've talked with people who have no body lift, that had a terrible time trying to remove the cross-over, even after dropping the cross member as suggested in Downey's instructions.

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.

Driver side header installed

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.

I was able to complete my installation without removing this hose, or removing the power steering pump from it's mount.

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, then remove 6 mounting studs as described in step #8.

13) Before installing right side header:

a) 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.

b) Use wire tires to insure all electrical and plumbing have adequate header clearance.

c) 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.

d) 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.

e) 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.

Check fit first!!

These instructions are very VERY important, do not forget to check for adequate clearance for all fuel lines, brake lines, electrical wire, etc. before using the vehicle. I found it easier to install my headers, and then move (or bend) all the lines away from the header once I had the headers in place.

f) 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!

Grind flange edge

This step is ABSOLUTELY necessary. Most everyone I've talked to has needed to trim the edge of the flange slightly to prevent interference with the mount for the power steering pump. If you have access to an angle grinder it will make this step as easy as the rest. Notice the difference in shape between the two sides of the flange. I found it necessary to take approximately 4mm of one side of my flange so that it would not interfere with the power steering pump mount.

14) 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.

Reed Valve Mouting

15) 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.

Reed Valve Pipe

As you can see, the supplied pipe will not connect to the header with the Reed Valve in its stock location. Downey's instructions call for the Reed Valve to be mounted atop of the supplied copper pipe, and no longer attached to the passenger side head. I decided to see if I could come up with a solution that would allow me to keep the Reed Valve in its stock location.

Many attempts

I purchased more 5/8" copper pipe, and attempted to bend it into the S-shape I'd need to make the connection. None of our MANY attempts succeeded. I ended up using the supplied stainless steel flex pipe for my Reed Valve instead of my EGR valve. This way I was able to leave my Reed Valve in it's stock location.

16) 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.

Final pipes

For my EGR valve I used the existing EGR pipe. The pipe does not fit in it's stock form...we had to severely modify the pipe to make it fit. It took CONSIDERABLE effort, but I'm very pleased with my installation. If I had to do it again I have no doubt I WOULD NOT try this same method. I would stick to the Downey method, and mount my Reed valve atop the supplied pipe.

17) Reconnect spark plug cords, both sides.

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

19) Reinstall air cleaner assembly.

20) Connect new tail pipes to new exhaust system.

21) Install Oxygen Sensor into the fitting on the new exhaust system.

As instruction #20 states, you will need a new exhaust system, or at a minimum a new cross-over. To get the maximum performance from these headers you should consider installing a high-flow 2.5" exhaust system. I chose to have a completely new and custom exhaust system made to compliment my Downey headers. The new exhaust system includes a 2.5" high performance Car-Sound catalytic converter with flanged ends, available from Downey.

Exhaust Routed Under the driveshaft

One possibility for the new cross over is to route it under the front driveshaft. Since the front driveshaft does not move vertically on an IFS vehicle, running the cross over pipe very close to the driveshaft will not cause a problem. This is not the best possible solution in that the cross over may be susceptible to damage on the trail.

Routed Around the Xfer case

A better option for the crossover is to route it back and around the transfer case. This will eliminate the possibility of damaging the crossover on the trail, and it will elimite the need to reroute your exhaust should you ever decide to do a straight axle swap on your vehicle.

I have now had two different exhaust setups with these headers. Based upon my experience I suggest running 2-2.25" pipe off of the headers, and when the two pipes combine to one, then bump up to 2.5" pipe the rest of the way out. This is the largest size exhaust I would recommend running. If you put too large of an exhaust pipe on your engine, it will not have the back pressure it needs, and you will actually LOOSE horse power and torque from your engine.

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