Plenum Options for 4.6 Ford V8

Above are the two plenum options we offer with the 4.6 ford throttle bodies. The one on the left is the stock mustang piece ported and on the right is the raised plenum design.

When designing a plenum for maximum performance there are a few considerations. Cross sectional area, how straight the air flow is, and velocity of the air. You have to balance out the three for the best performance. If you simply hog out as much metal as possible you are making the largest area inside the plenum however you sacrifice the velocity of the air coming through.

For the ported stock plenum we match the throttle body and open up the casting throughout which is a nice increase in power and flow over stock.


It is best to match the inlet to the throttle body and then to straighten out flow as much as possible. it makes no sense to make the inside of the plenum bigger then the throttle body since this will simply hurt velocity and not increase volume, the throttle body would be the limiting factor in flow. This straightening is where the raised plenum helps.

 

If you look at these two next to eachother on the stock mustang throttlebody you can see the air has to make a 90 degree turn. On the raised version it is a much more gentle transition. This keeps the velocity and airflow up.

To further straighten flow we port the edge of the opening into the intake to the edge of where the gasket will sit. The short side radius (inside corner) is also ground down about half an inch in the center, increasing cross section and decreasing the sharpness of the transition.There are some aftermarket versions like the picture below that greatly increase the area on the top

As you can hopefully see this actually does the opposite of straightening out flow!

The vacuum lines are routed in a slightly different manor on the raised plenum and it has one extra port. Please do not order this if you are not comfortable with re-routing the lines a bit. It is easy enough to do but worth mentioning. 

Ford 4.6 V8 Mustang Crown Vic Ported/Halfshafted throttle bodies

When porting these throttle bodies we use a variety of techniques to increase airflow through your engine economically. When you look at a stock unmodified throttle body there are several issues to deal with when you start looking at airflow. The oem design is made to cheaply produce not necessarily maximize performance. The biggest flow improvements come from what is known as Half Shafting the throttle body. This is where the top part of the throttle shaft which holds the throttle plate is removed to allow more airflow. I go one step further and Quarter Shaft the throttle plate by removing about 1/4 of the remaining side of the shaft. This picture shows in red how much of the shaft has been taken out of the airflow path:

This is a good start to improving flow however if you use the stock screws to reattach the throttle plate to the shaft you have another object sitting out in the way of flow. To prevent this issue I use beveled screws and countersink them into the throttle plate. I also remove the end of the screw protruding from the back of the shaft so there is no turbulence or reduced flow from these jutting out into the path of airflow.

To compliment these modifications I also make sure to smooth the airflow transition from the throttle inlet as well as the transition to the intake manifold. The less turbulence produced in these transitions the more air will flow through. Do Not use throttle body spacers that claim to improve performance by introducing turbulence or swirl by the throttle body. The only time turbulence improves performance is when it is about to enter the combustion chamber or when fuel is flowing through that part of the intake. Neither is the case with your throttle body, the fuel is injected into the lower intake as close to the heads as possible and the air will have to straighten as it goes through the individual runners negating any swirl effect that could possibly help.

The throttle plate on most throttle bodies doesn't open to be totally perpendicular to the airflow, as such the plate is creating another restriction by being at an angle. It can be surprising how much of an angle these come stock with. I remove just enough of the throttle stop to allow you to fully open your throttle.

Finally I finish off the throttle bodies with a ceramic black high temp paint for a clean look that wont clash with any under hood color combination.  

I offer these throttle bodies for 99$ + refundable core charge Currently I can get good used cores for these engines for about 40$ however this charge is subject to market price/availability. Core charge is refunded upon receipt of a usable core.

Ford V6 3.8 Mustang Ported/Halfshafted throttle bodies

When porting these throttle bodies we use a variety of techniques to increase airflow through your engine economically. When you look at a stock unmodified throttle body there are several issues to deal with when you start looking at airflow. The oem design is made to mass produce not necessarily maximize performance. The biggest flow improvements come from what is known as Half Shafting the throttle body. This is where the top part of the throttle shaft which holds the throttle plate is removed to allow more airflow. I go one step further and Quarter Shaft the throttle plate by removing about 1/4 of the remaining side of the shaft. This picture shows in red how much of the shaft has been taken out of the airflow path:

This is a good start to improving flow however if you use the stock screws to reattach the throttle plate to the shaft you have another object sitting out in the way of flow. To prevent this issue I use beveled screws and countersink them into the throttle plate. I also remove the end of the screw protruding from the back of the shaft so there is no turbulence or reduced flow from these jutting out into the path of airflow.

To compliment these modifications I also make sure to smooth the airflow transition from the throttle inlet as well as the transition to the intake manifold. The less turbulence produced in these transitions the more air will flow through. Do Not use throttle body spacers that claim to improve performance by introducing turbulence or swirl by the throttle body. The only time turbulence improves performance is when it is about to enter the combustion chamber or when fuel is flowing through that part of the intake. Neither is the case with your throttle body, the fuel is injected into the lower intake as close to the heads as possible and the air will have to straighten as it goes through the individual runners negating any swirl effect that could possibly help.

The throttle plate on most throttle bodies doesn't open to be totally perpendicular to the airflow, as such the plate is creating another restriction by being at an angle. It can be surprising how much of an angle these come stock with. I remove just enough of the throttle stop to allow you to fully open your throttle.

Finally I finish off the throttle bodies with a ceramic black high temp paint for a clean look that wont clash with any under hood color combination.  

I offer these throttle bodies for 79$ + refundable core charge and shipping. Currently I can get good used cores for these engines for about 40$ however this charge is subject to market price/availability. Core charge is refunded upon receipt of a usable core.