I had already changed the rear part of the exhaust system. But I wanted more. More power. So, finally I decided to change the original exhaust collectors to a set of exhaust headers.
The main problem with the original collectors,
is that the gases from the right side are routed behind the engine and dumped into the left collector,
all too close to the exhaust ports in the left cylinder head.
This is very restrictive on the gas flow.
Plus, that a header system,
with it's larger tube diameter is always less restrictive on the flow.
The Downey headers look good. But, the attaching Y-pipe route under the clutch housing. And Downey very clearly states that it will not fit with trucks where the front diff has been lowered. Since my Mega Runner is raised four inches with a kit from Trailmaster, this was obviously not an option for me.
Finally, I chose the headers from
NorthWest OffRoad Specialities (NWOR).
They retrofit all original equipment and they are gasket free.
Being gasket free is a bonus to me,
since
I live
in
France
and getting new gaskets sent to me from
the US
will always take a while.
Their Y-pipe route on both sides of the gear box,
and connect to the catalytic converter just behind the transfer case.
Installation is a pain.
I was forewarned,
but still much troubled.
The most difficult part is to remove the old collectors.
Downey talks about lowering the gear box to remove the crossover pipe from behind the engine.
This is not mentioned in the installation instructions from NWOR.
They claim that it is possible to remove the pipe by sliding it out through the left wheel well.
I managed to do that,
but only after having cut a triangle with the size of about one inch on each side.
Also, reaching all the nuts holding the old collectors requires small hands and a very good set of metric tools.
I actually spent 25 minutes with one of the nuts before it was completely off.
Gasket free headers. Sounds nice, doesn't it? Well, it means that instead of a stiff gasket, one must use 'gasket on tube', a paste forming a gasket when applied and heated up. This was not mentioned in the catalog from NWOR. And of course, no such paste was delivered with the headers. There was only a vague statement of 'using the red paste'. I chose to use a paste from Loc-Tite. It's actually red in color. This paste is sold for the purpose of creating a gasket in very hot environments, for instance between cylinder heads and exhaust systems. On specific request: LocTite Ultra Copper, part number 24438.
The right header didn't fit 100%. I had to remove and grind about two millimeters on the mounting bracket for the power steering pump. This is not a very difficult thing to do, but it's tricky to perform without detaching the tubes to the pump, and also without purging the power steering oil. I managed, without getting oil spread all over the place. The left side fit perfectly.
To make sure that the gasket paste was heated up as soon as possible after the mounting, I started the engine before having mounted the Y-pipe. This was about eleven o'clock in the evening. My neighbors actually came out in their garden to see what was going on. The sound is impressive, but illegal.
After having mounted the headers, mounting the Y-pipe was just a breeze. On my European 4Runner, I had to move the exhaust system backwards about one inch. Actually, I cut the pipe between the catalytic converter and the muffler, so that the rear part of the exhaust was still in the same place. All pollution control units fit perfectly to the system.
They are not very visible. And they get blue and violet after only a few hours. Also, count on a raised temperature under the hood. Anyone knows where I could get two small but beautiful scoops to my hood?
