1969 Pontiac GTO

There are a few things to look at:

Check the play in the clutch linkage. Sometimes new stuff will change dramatically after break in. See if there is excessive play and check the play at the clutch arm where it contacts the linkage.

Even if the pressure plate is new, there is the pssibility that a finger broke. Is it a 3 or 4 finger pressure plate or is it a diapraghm type, (where there are fingers all the way around)?

Are the motor mounts new?

Is there any change to the vehicle that is different than its original setup, such as: changed motor from small block to big block, different type of tranny, heavy duty or multi-plate clutch, etc?

Let me kow and I will keep this post on my list. I will get back with you ASAP and see if I can help you out.

There is an adjustment for free play in the pedal. This is generall as tight as you can get the linkage without it dis-engaging the clutch without the pedal being pressed.
I adjust mine at the arm that sits on the throwout bearing. It is really the most accurate way to get the most dis-engagement when the pedal is pressed. I tighten the linkage until there is just a little bit of free play without the throwout bearing riding the pressure plate. This way when you press the pedal it will move the throut bearing as much as possible without the clutch risking not being fully dis-engaged when the pedal is releaed.
Also, with a custom job from A/T to M/T the linkage alignment can be critical depending on the setup. If the linkage is mounted strictly on the motor and tranny the alignment is less of an issue as opposed to the linkage being mounted on the chassis.
If you had to weld linkage in place somewhere on the chassis or custom fabricate something, I would try to get measurements form a stock setup oir maybe call the tech line at Center Force.
Let me kow how it goes.

There are also some good links on this site for diagnosing the issue. But, I don't think there is anything that will have specs or measurements as that would be found in a factory service manual. The Mitchel ! Online maual offered on this site is a great deal because you get service manuals for essentially any car that you own or ever will own.

I will check back to see how it is going.

Couple of things tocheck here. Take a bar and with the engine off, push the harmonic balanecer forward. If it moves more than a couple of thousands then you have a worn crank thrust bearing and when you push the clutch in it is actually pushing the crank forward. It can also be a broken crank at the back two journals. It can also be a bent release arm. It's going to be one of those assuming your clutch is ok.

Sorry I was out the month of December.
Hmac brings up excellent points to check that could be the cause.
I think he mnay be on the right track as your clutch is new and as long as you installed it correctly. Centerforce is a good clutch and it is unlikely that something is wrong but not impossible.

Thanks to hmac300 for covering during my absence.
We aim to please!

I am back in action and I am sure both hmac and I will keep an eye on the outcome and help any way we can.

Take care.