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Figure 1 From left to right, a new PI Ford Triton...
Figure 2 On the left you can see the deflector tu...
Figure 3 The gasket on the left is the original g...
Sometimes Engineering Changes Actually Make Sense
The following information is in reference to the thermostat bypass port that is found only on the left side cylinder head of all PI (Performance Improved) Ford Triton engine applications; the 4.6L and 5.4L V8 engines as well as the 6.8L V10.
By Roy Berndt
As much fun as it is to play detective, research obscure facts and
unravel engineering messes myself, sometimes I totally enjoy running
across things that just plain make sense.
Often, many of these things are after-the-fact thoughts, but that is
why hindsight is always 20/20. For those in the engineering world,
these would be running changes, technical improvements and developments
or improved reliability changes, but all of them mean the same thing:
we found a problem and we fixed it.
Let's start with the problem: poorly maintained coolant will become
acidic and/or alkaline, and a poor engine ground will allow the coolant
to become charged. Each of these is just one of the potential coolant
corrosion problems facing these engines, and both of these will have a
caustic effect on aluminum. The result is erosion of coolant ports
which may cause a gasket leak and/or coolant leak of the casting
integrity itself (see Figure 1).
Ford has made a couple of improvements to help eliminate the erosion in
the thermostat bypass port. One is the addition of an anodized steel
thin wall flow tube. This insert (p/n 1L3Z-6G017-AA) has a slight flare
at the top to seat it into the coolant bypass port (see Figure 2).
Next a change was made to the intake manifold gasket. Not only does
this accommodate and hold the tube in place, for a cylinder head that
does not have the tube installed it creates a much better seal in that
area. This intake gasket upgrade happened in 2001 and you would think
that everyone would know about it by now.
The part number for this gasket is 1L3Z-9439-BA and I have only been
able to locate it in the aftermarket from Federal-Mogul/Fel-Pro (p/n
96281) and in manifold sets MS9628 and MS9628-1 for the V8 applications.
If you look carefully at the photos in Figure 3 you will see that there
is an additional layer of rubber that makes the gasket passage smaller
but has no impact on the bypass port.
Therein lies the fallacy; there are many references to this later
gasket as a "restricted port" gasket but this is not the case. It is
simply an improved sealing and retention device for the flow tube.
Another option is that the right side cylinder head is not impacted by
this scenario. Therefore, if the left side head has erosion you do have
the choice of using it on the right side and the right head on the left
side. Obviously if you're selling cylinder heads as individual
components the erosion will need to be repaired and the intake surface