Mid Port Engine Build
reasons. Right now I have a nice shop available to do the work and also have another vehicle to
drive while the project is in process. I've learned that it's a lot easier to do this sort of job on terms
like this rather than waiting for something to break. Also, after putting almost 60K miles on the car
(including almost a year of commuting 125 miles a day in traffic to San Francisco), my clutch has
been chattering when cold lately. Obviously, I would like to get some more performance out of it as
well.

package. This gives me a stronger crank, a stronger block with a knock sensor, and I'll be replacing
the heavy small port rods with a set of lightweight 20V Blacktop rods. The block is being bored .5mm
oversize so that everything is tight and fresh. I'm also using Total Seal gapless rings to insure that I
get the most out of my combustion. The replacement pistons are 10.3:1 compression and I'll be
using a TRD .8mm head gasket along with a compression cut on the head to get my effective
compression ratio up to about 11:1

I'll be re-using my low-drag water pump and overdrive pulley, as well as the under drive pulley for my
alternator. I also bought a light crank pulley from TechnoToyTuning to drop another couple of
pounds of rotating mass.

The entire rotating assembly will be balanced for smooth operation.
The cylinder head and intake is what will set this build apart. I'm building a "mid-port" engine. This
will eliminate the TVIS setup but also should work better than either the original large port head or
the later small port head.

To me, the TVIS system was a good idea to mask on overly large intake port design error and help
to make it more streetable for the average driver. It does a good job of that, and for a high RPM, high
output race engine it is a very good head - typical of the Yamaha designers who created it. The small
port head was (to me) a cost saving way to continue producing an existing engine. By eliminating
the TVIS setup and reducing the port size, the same basic function was achieved. The good news is
that the small port intake manifold is far superior to the TVIS intake in terms of flow and RPM range.

So, to me the best thing is to build a mid port engine that combines the best of both worlds. Since
the small port head can't be ported out enough to do this without breaking into the water jackets, I'm
taking my original big port head and using Devcon Aluminum Putty (an epoxy) to reduce the size of
the intake ports.

I've roughed up the surface of the ports so that the Devcon has a better surface to stick to, and also
added some deeper grooves to help anchor the epoxy. I've also made individual styrofoam "interior"
molds that should be the final shape of the port. Each foam insert was shaped to fit a specific port,
as each one is slightly different (this IS a production part after all...). Each one was labeled and
marked for easy identification. I used clay to fill in the injector bosses since I don't want to change
those areas at all.

Here are some pictures so that things make more sense:
I had to make the inside end of the
cores pointed so that I got a tight fit.
Here are four shots of the intake manifold
machine work in progress. You can see
that to build the manifold correctly I had to
mill through the aluminum casting and
into the epoxy I had used to block off the
center sections of the manifold from my
"try a small port intake on a big port head"
experiment.
Pics below are the work in color
differences how much material is
being added to the injector ports
was important.

The styrofoam cores dragged
epoxy down farther than I thought
they would, but nothing I can't fix.
I also started to pocket port the
head, just to smooth out the
transitions from the head casting to
the seats. You can see the factory
machined area and also some of
the core shift that leaves material
hanging out into the port - that's
I've added some more pictures from the assembly.
Most of it is self-explanatory, but I'll add more info soon.
On the left is a stock small port gasket laid over the mid port manifold. The next two are a stock
big port gasket laid over the mid port manifold.

You can see from this that the mid port floor is raised quite a bit, wider than a small port, but not
as wide as a big port.
This is the chamber
after porting away the
casting humps shown
in the top photos.
One of the small port head "features" is what most people think is an oil drain in the
drivers side rear of the head with a matching hose and fitting in the engine block.
Supposedly this addressed a problem of oil pooling up in the head on hard
cornering. The problem with that idea is that this area is much higher than the
existing oil drain ports in the head.

In the Toyota parts book this "drain" is clearly called a "crankcase vent". Since the
description sounds like it's part of the pollution control system, I made sure to add it
in as part of the build. I used the same Devcon aluminum putty to fill in the exterior
corner of the head, then pushed in the metal fitting that I had intended to thread in
after it had set. While I was doing this I realized it would be much easier to just sink
the fitting into the putty and let it harden. It sat overnight, and then I just carefully
drilled through from the backside. It was much easier and quicker doing it that way.  
machined 1 tooth off - that
explains the problems I had last
year!

Also pictured are the oil squirters,
the really cool Blacktop rods, the
small port pistons with the cutouts
for the squirters, the engine just
before re-installation and the
Dynamat Extreme sound
deadener.