SBC Pressure Plate Damaged (PICS)

[Artago]

Got the engine out of the car. Noticed some damage to the pressure plate.

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There were 3 of these. I lost 1.

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I found all 3 of those tabs in the bell housing.

What do these tabs do?
Do I need them?
Can I re install the pressure plate?
Or should I replace it?

Thanks, Tom

 

[snowborder714]

Did you happen to get it from Tim (twicks69)? If so, I'd get in touch with him and ask. And even if you didn't, I'd send him a PM and get him to reply to this thread

 

[crimsondragon]

My guess is it holds contact part of the pressure plate to the top. It looks similar to my Centerforce except theirs offsets away with bent steel. Were you having engagement issues? I bet if you took the plate off the flywheel it would fall apart. SBC seems to blow.

 

[Artago]

Did you happen to get it from Tim (twicks69)? If so, I'd get in touch with him and ask. And even if you didn't, I'd send him a PM and get him to reply to this thread

I did get it from him. Send him a PM about. Will call him tomorrow.

My guess is it holds contact part of the pressure plate to the top. It looks similar to my Centerforce except theirs offsets away with bent steel. Were you having engagement issues? I bet if you took the plate off the flywheel it would fall apart. SBC seems to blow.

Not sure about the engagement issue. I think is was all good. Ran fine for 10,000+ kms. Hard to get it into gear but that could just be the synchros. Been like that for a long time. Stock tranny had 250,000 kms on it. Just replaced it with a rebuilt.

I took the pressure plate off and it seemed ok so I reinstalled it. Then I noticed the damage. I'll remove it again and take a few more pics.

Not sure what's going on.

 

[Artago]

Updated the pics.

 

[sirbow2]

I can't see the pictures; just little grey access denied logos.

 

[Artago]

I can't see the pictures; just little grey access denied logos.

Sorry about that. Google photos permission settings...

Can you see it now?

 

[Artago]

Update: Heard back from Tim. He's contacting SBC for me. Tim said that it looks like the clutch was over extended. Not sure how I can check that. I adjusted the pedal myself according to Jack's video.

I wonder if those tabs are just a stopper or if they are required for the normal operation of the clutch. If they are not needed then I should be able to readjust the clutch throw and reinstall. If they are functionally required them I'll need a new pressure plate.

Thoughts? Opinions?

 

[delta448]

My guess is it holds contact part of the pressure plate to the top.

Yep.

Tim said that it looks like the clutch was over extended.

My thoughts as well.

I wonder if those tabs are just a stopper or if they are required for the normal operation of the clutch. If they are not needed then I should be able to readjust the clutch throw and reinstall. If they are functionally required them I'll need a new pressure plate.

Thoughts? Opinions?

It appears those tabs keep the friction surface of the PP attached to the spring diaphragm. They ensure the friction surface lifts off the clutch disc when you push the pedal. They likely broke because the TOB pushed the fingers of the diaphragm so far toward the flywheel that the inside diameter of the friction surface levered against the diaphragm or another feature inside of it.

If you want to make sure this doesn't happen again, you need to adjust the clutch pedal to have less travel left over after disengagement.

 

[crimsondragon]

What's odd though is if it was over extended and broke off, there doesn't seem to be any contact marks on the pressure plate where it would hit. I don't see any wear marks in the photos or any marks except for a slim sliver of paint missing on the edge. However, it seems it did make contact, albeit with some force on the corner; my guess is it broke off, hit that corner as the pressure plate rotated and was ejected. If that's the case, I wonder if the tabs failed from vibrations and engine harmonics.

 

[Artago]

They likely broke because the TOB pushed the fingers of the diaphragm so far toward the flywheel that the inside diameter of the friction surface levered against the diaphragm or another feature inside of it.

If you want to make sure this doesn't happen again, you need to adjust the clutch pedal to have less travel left over after disengagement.

Sort of what Tim said but I'm still having a hard time visualizing it. Don't know enough about pressure plate mechanics.

Are those tabs just stops for the outer diameter of the diaphragm spring?

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More importantly, how do I make sure I don't have too much throw on the next pressure plate? (or too little)
I adjusted the pedal / slave / master for maximum throw. If I tone it back how can I find out if I'm in the "sweet spot"?

 

[motomattx]

The piece that broke pulls the pressure plate face away from the friction disk, with it broken the clutch will disengage but not as cleanly because when you press the clutch pedal the pressure is being removed from the friction disk and pressure plate stack but its not being "pulled" apart, because its not being forced apart and just being enabled to "slip" you wont get as good of a disengagement.

 

[Sebba]

If that happens it can also damage your synchronizers. I would not drive the car.