Who is running a blower w-C4 trany

[TOM B]

Who is running a blower with a C4 trany in you classic.
What did you do with the vacuum modulator line.
How did you get it to shift right.

 

[10secgoal]

I just saw this in a different thread on another site I think. I don't remember what exactly they said, sorry. But you could change the stock valvebody to a manual for like 75 bucks. If you must retain it, go to Fordmuscle.com. They have a c-4 forum there and it is FULL of c-4 guru's. Hope that helps.

 

[Fostang]

a one way check valve from an 80's toyota brake booster.

 

[Fostang]

Don't forget to pick up a pcv valve for an 88' turbo coupe preferably a ford oem part.

 

[10secgoal]

How will that help ? The vacuum modulator crontrols line pressure from vacuum. The boost will cause positive pressure. How will the one-way change that ? Just curious.

 

[TOM B]

Hmmm A manual valve body. Its one of the early C4 tranys and is a 3 speed. I dont know anyone who sells this kit.

 

[10secgoal]

Hmmm A manual valve body. Its one of the early C4 tranys and is a 3 speed. I dont know anyone who sells this kit.

Trans-go does. I used it, and love it. It's a shift kit, and if you go through it and change a few more parts that are supplied, it changes it to a complete manual valvebody. Ithink they even sell them on e-bay for 57, but then shipping and what not. You may be able to save a few bucks.

 

[TOM B]

I went to the transgo web site and they dont sell a full manual shift kit for my early c4,,, its a 65 model c4, what year is yours 10secgoal. does any one else sell these

 

[mdjay]

Most trans build shops will know about the swap to manual kit!

 

[Fostang]

How will that help ? The vacuum modulator crontrols line pressure from vacuum. The boost will cause positive pressure. How will the one-way change that ? Just curious.

When you go into WOT there is no vacuum. It should be at 0. Then when boost kicks in it pushes the one way check valve shut thus not allowing the boost to screw with the vacuum modulator.

Under normal driving there should be no boost thus the transmission will operate no problem.

 

[10secgoal]

When you go into WOT there is no vacuum. It should be at 0. Then when boost kicks in it pushes the one way check valve shut thus not allowing the boost to screw with the vacuum modulator.

Under normal driving there should be no boost thus the transmission will operate no problem.

So why not just diconnect and plug the vacuum port. I mean when he gives it a little more than normal gas, the blower going to create boost and be blocked. So essetially the modulator never gets any reading, right ?

 

[Fostang]

So why not just diconnect and plug the vacuum port. I mean when he gives it a little more than normal gas, the blower going to create boost and be blocked. So essetially the modulator never gets any reading, right ?

No sir if the blower is functioning how it should it does not make boost at part throttle.

 

[10secgoal]

No sir if the blower is functioning how it should it does not make boost at part throttle.

So how high of a load before it makes boost ? On an average, I realize rootblowers, the lag and that crap. But when it does build boost, and the line is blocked, how will the line pressure be raised in the tranny, and adjust the shift points ?

 

[mdjay]

about 2500 rpms or so...

 

[302 coupe]

I would suppose that since the tranny's modulator sets the firmest shifts for 0" vacuum(which when n/a would mean wide open throttle), that when blown and equipped with the check valve it would still shift the hardest at 0" vacuum. In a blown application, 0" vacuum could occur at nearly any rpm or throttle position(except closed). If your blown engine reachs 0" vacuum at half throttle, then your trans will now shift its hardest at half throttle b/c the modulator would normally interpret 0" vacuum as WOT. Because of this, I would say that some means of boosting line pressure would be strongly recommended in a blown application.

 

[TOM B]

someone has to have an answer to this, Im not the first one to put a supercharger with a C4...

 

[mdjay]

Tom, I had one on mine and used a manual shift kit as mentioned above. It worked fine but I wanted a five speed so I swapped it out...