How to optimize the stock or SVT TB Posted By: Crispy
These modifications will provide a significant improvement to throttle response on the 2.5L Duratec engine.
Total work time to perform the modification is about 2-3 hours at a cost of under $2. The modifications will
provide the following improvements:
** Improve air flow and air flow volume by replacing the round-head philips screws holding the throttle plate
with countersunk screws.
Countersunk screws are completely flat in relation to throttle plate.
** Improve air flow and air flow volume by reducing the air flow interference caused by the throttle body shaft
and protruding screws.
The back side of the shaft and protruding screw threads are milled flat.
Parts and Tools Needed:
Metric socket set - 1/4" drive
Medium and fine 10" flat files
Fine & extra fine emery cloth
Phillips screwdriver
Bench vise (recommended)
2 - 4mm flat-head countersunk machine screws (Home Depot or Lowe's)
Rubbing compound or metal polish.
Carburetor or throttle body cleaner
Step Procedures
Start off by removing the air box with IAT sensor, and the throttle cable linkage. Disconnect all of the hoses to
the rubber accordian intake hose. Disconnect the MAF and throttle position sensor electrical connectors and
remove the accordian hose from the throttle body. (TB)
Remove the four 8mm bolts holding the throttle body to the upper intake. Remove the throttle body and gasket.
Stuff a clean rag in the intake port. (Clean this area up later with throttle body cleaner and a toothbrush.) If the
gasket is torn or damaged, obtain a replacement.
With the throttle body on the bench, remove the 2 screws holding the throttle position sensor (TPS) taking note
of it's orientation before removal. (The screws are very tight!)
Note the throttle "butterfly" plate top and bottom side and remove it from the shaft by removing the 2 phillips
head screws. Clean the TB shaft with TB cleaner and soft rags.
Relieve the spring tension and withdraw the TB shaft.
Put the TB shaft in a vice with the "half round" side opposite the throttle plate recess facing upwards. Use a file
or dremel to machine the section behind the recess to about 1/16" thickness. Smooth out with emery cloth in
fine and extra fine grades.
Using a fine file, carefully sharpen the leading top edge of the butterfly plate. Don't change the diameter of the
plate or disturb how the back side of the plate will close within the bore of the TB, or idling problems could
result. (Optional step)
Using a 3/8" drill bit, carefully create countersinks in the butterfly plate where the screw holes are. The idea is
to bevel the existing holes so that the new countersunk flat head screws will fit flush with the plate when
everything is screwed together.
Assemble the butterfly plate on the throttle shaft using the 4mm countersunk flat head screws. Use extra fine
emery cloth to smooth the top surface of the plate. Next cut or file off any screw threads protruding out of the
back side of the (now flat) TB shaft.
Remove the butterfly and then polish the plate and center portion of the shaft using extra fine emery cloth.
Finish with rubbing compound or metal polish.
Reinstall the TB shaft, spring, and TPS onto the TB. Making sure everthing is positioned correctly by testing
the rotation/return of the TB shaft. Position the butterfly plate on the shaft and attach with the countersunk
screws. Use a drop of lock tight on the screw threads. Check that the throttle plate and shaft rotate the full 90
degrees without any interference.
Remove the rag from the intake port and clean the EGR ports using TB cleaner and an old toothbrush. Reinstall
the throttle cable on the throttle shaft cam and then reinstall the TB and gasket. Install the throttle linkage plate
and the rest of the intake components including the hoses, MAF and TPS electrical connectors
thanks to the folks at CEG