Fords GT40P
Intake Port


The Ford GT40P intake port looks pretty well designed and cast in its stock form. After working with it, I have found that it is not very easy to improve on, for an amature like myself.

Let's see what can be done to a Ford GT40P intake port!

The plug boss has a small area of obstruction for incoming charges.

A threaded wand shows a very strong and stable flow in this area. More on using
threaded wands in my up coming web site.

The plug boss is trimmed a bit. Testing did not indicate any changes in flow
with the plug boss cut back.

The short side radius is pretty well cast as-is. Only a small amount of
smoothing will take care of the slight ridge. No improvements in flow were
detected with the smoothing of the short side radius. Port enters from the upper
right corner.

The intake throat under cuts the seat on the out board side, near the cylinder
wall. Smoothing the sharp ridge here, where the throat cut meets the casting,
showed a significant improvement at .1" and .2" of
lift. Don't flatten it or straighten the side, just apply a smooth radius. Port
enters from the right side.

The back wall of the throat has a slight ridge where the throat cut blends into
the cast bowl. Smoothing this transition showed no flow improvements. Nor did
any work on the inboard side of the throat. Port enters from the bottom.

The intake throat short turn radius, out board side under cut and back wall
smoothed with a Dremel and small stone. Port enters from the upper right side.

After marking the cylinder line around the head deck surface using a gasket as a
guide, the chamber wall is cut back to unshroud the intake valve.

Lifting the intake valve to .5" brings the valve face closer to the chamber wall
again. More clearance can be cut here. Unshrouding the intake valve showed
impressive pressure drops to .3" lift with a slight
drop at .4".

Trimming the valve guide with a Carbide burr marked good flow improvements
across the entire valve lift range.

Under cutting the intake valve 30 degrees, .070" wide, improved flow at .1" and .2",
but at .5" lift lost significant flow
while .3" and .4" saw no real change.

Using a FelPro 1250 intake gasket exposes a little material on the short side
radius wall and port floor

The slight push rod bulge on the long side radius wall can easily be smoothed
down flush with the wall, and also showed a slight improvement in flow at .2"
and .3" lift. .1" lift lost a bit of flow.

Cutting the floor down to the gasket line really helped out at .4"
and slight increases at .3" and .5" too, but .2" took a hit with a loss
as well as .1".

Cutting the short side radius wall back to the scribe line took its toll on .1"
again since we scribed the gasket line, but .5"
saw a small gain. Increasing the radius of the wall improved flow at .4"
and at .5" and .1" was very happy with the
bigger radius with a good increase in flow but .2" lift took another loss in flow.

What the Hell was I thinking with this exhaust exit? Click here to find out.
More good stuff!