Once you've gotten a feel for the carbide cutter, you can
start with the exhaust ports. The first step is to mark the
gasket match boundary. This will define how much you should
open up the port. You should use the exhaust header gasket
which best matches your headers. It is critical that the exhaust
port not be ported larger than the size of the header flange
opening. If the exhaust port is larger than the header flange,
gases exiting the port will hit the flange and create turbulence.
The objective is to have a smooth transition from head to
There are alot of cheap paper header gaskets out there, and
most of them have awkward port sizes. We've found the Fel
Pro 1415, as well as the Mr. Gasket Ultra Seal to be the best
gaskets, in terms of port size (1.25" x 1.48") and
also durability. Mount the gaskets using a couple of header
bolts and some tape so that all of the holes are evenly spaced
around your ports. Then use permanent ink marker to trace
the edges of the gasket ports to the head surface. Finally,
you can use a sharp scribe to make permanent edge limit markings.
You should also check the gasket against the headers, and
port the flanges to match the gasket. Most headers have a
fair amount of welding slag and excess flange material hanging
into the pipe from the manufacturer. Cleaning this up will
help significantly, but be cautious not to grind the welds
or flange too thin.
Now that you have your outlines ready- start your grinder!
The exhaust ports are the best place to start. Looking at
the 'before' picture to the right, you can see the typical
restrictions that are in most Windsor heads. Typically there
is a lip on the roof at the mating surface, even as much as
1/16" piece of flash hanging there. If you have '66 or later
heads with the smog bumps, they will be first to go. This
is where you really should use a carbide bit. If you can combine
that with a high-speed grinder, those bumps will be history
in no time. This is another place for learning the feel of
your tools. By the time you cut down all eight bumps you will
be more confident in your abilities. Take the bumps down until
they are even with the surrounding roof.
The valve guide boss is next. It does not protrude far into
the port, but it does form an unneccesary obstruction, so
grind it down. Most machinists and professional porters agree
that there is plenty of iron above the port to secure the
valve guide. Some shops will cut the new bronze valve guide
flush with the roof, others leave it the full length. It's
really a matter of preference. On aluminum heads, however,
a full guide is recommened for stability.
There are many "generic" porting articles that say
to only go about an inch into the exhaust port. That may be
true for Chevys but is absolutely wrong for the stock Windsor
heads. To make the walls and roof straight you will need to
go almost all the way to the back of the runner. If you check
your stock exhaust runner you will see, and feel, how it is
actually smallest at the opening and larger at the back of
the bowl. This is backwards from what it should be. You want
your exhaust port to stay a consistent shape or even expand
a small amount so flow is not impeded. Unlike the intake port,
which has cooler air/fuel mixture being drawn in by the vacuum
created from the downward moving piston, the exhaust gases
are very hot and under high pressure and will take the fastest
way out. The straightest port is the best flowing port. When
you finish gasket matching, the walls, floor, and roof should
either be straight or taper larger as you move from the bowl
out to the port.
The runner then turns up a few down degrees to the valve seat.
If you look at the pictures of our ported head you can see
that it is almost a straight line from the port opening to
the back of the bowl. The exhaust gases will flow best if
they don't have to change directions. By the time you have
made a nice straight roof you will have hours of grinding
time under your belt.
Finally, the bowls need attention. Referring to the picture
of the stock bowls, there are a couple of major ridges in
the exhaust port throat that need removal. The first one is
on the short turn radius. This ridge only needs to be ground
smooth. Do not change the shape of the turn! This is where
experience counts and inexperience can get you into trouble.
If the radius is reduced too far your flow will suffer because
the gas will have too tight a turn to make and become turbulent,
slowing the gas velocity. So our advice is to stick with the
sanding rolls when working the short-turn radius in both ports.
There will be small ridges just under the valve seat from
the machining process. Smooth these with the sanding rolls.
Remember, you should get a three-angle valve job after you're
The last step will be creating the proper surface finish.
For most applications going over the entire port and bowl
area with the 80 grit (or "Fine") sanding rolls will suffice.
For that last little bit of flow you can polish the surfaces
to a mirror finish using a carbide impregnated rubber bit
in the Dremel tool.
Shown here is a typical combustion chamber on a stock
Ford windsor head.
Note the protruding valve guide boss. Grinding this flush
with roof will increase flow dramatically.
Also note the ridges below the valve seat. Smoothing these
out helps reduce turbulance; getting the gas through the
Tip: Use your index finger to probe the stock ports.
Follow the path of the gasses. On the exhaust port, stick
your finger in through the bowl, and on the intake side,
start from the intake port opening. Get a feel for all
the obstructions, the surface of the ports, the ridges,
bumps, and irregularities. Everything that feels like
an obstruction to your finger, is impeding air flow, and
needs to be worked on.
Here is a close up of the exhaust bowl. The valve guide
boss has been blended into the roof. The ridges in the
throat area have been smoothed down. The entire exhaust
port has a slight taper from bowl to exit. Finally the
entire area is polished with fine grit sanding rolls.
Imagine how different this port would feel with your fingers,
compared to the stock port.