Moparts

Thrust bearing wear with B&B clutch

Posted By: hemienvy

Thrust bearing wear with B&B clutch - 05/01/22 03:56 PM

Has anyone had abnormal thrust bearing wear when using a B&B clutch at over 3000 lbs clamping ?

Any problems with the Z-bar shaft or linkage components bending ?
Posted By: CKessel

Re: Thrust bearing wear with B&B clutch - 05/01/22 05:23 PM

When I had my Duster, I reinforced the Z bar by adding gussets 90* to the arms and the tube. Added additional material to the arms, with a hole in it, so that there was 360* of weld attachment of the arms to the tube. Disabled the clutch switch so I didn't push the clutch in on cold/no oil pressure starts[ personal preference on this, up to you]. I have np pictures of the completed Z bar to show you unfortunately. Also put a torque strap on the lh side of the block to the k-frame, helps higher rpm shifting when you try to push the clutch in. I also modded the clutch fork and the lower Z bar arm to take Heim joints.
Posted By: fourgearsavoy

Re: Thrust bearing wear with B&B clutch - 05/01/22 05:59 PM

The wear will not be "abnormal" as stick cars will always put additional wear on the thrust bearing. This is why I prefer later model blocks with a larger thrust bearing surface. As stated above do not push the clutch in on cold starts. Just pay attention to your driving style and don't hold the pedal down when stopped for extended periods. I quit running those heavy clutches years ago with the modern advancements in clutch technology there is no need for so much pressure.

Gus beer
Posted By: Cab_Burge

Re: Thrust bearing wear with B&B clutch - 05/01/22 06:03 PM

Make sure the throw out bearing is not riding on the pressure plate arms with the clutch pedal is released scope up
I've had many stock Mopars with the big over center spring under the dash hold the throw out bearing fork partially down, it will not allow the fork to release all the way unless I would use my foot to push it up all the way past the pressure on the pedal by that dang spring rant scope
If you adjust the linkage properly it will allow the pedal to release all the way up but it ends up having less than 1/2 inch of pedal travel to start pushing the throw out bearing on the pressure plate arms wrench up scope
Posted By: kwikblownhemi

Re: Thrust bearing wear with B&B clutch - 05/01/22 06:43 PM

I've been running 3000lb B&B pressure plates for fifty one years in my Hemi street/strip car. The engine has had a few rebuilds in 150 k miles but never any z-bar problems or abnormal thrust bearing wear. I beat on it often.
Posted By: madscientist

Re: Thrust bearing wear with B&B clutch - 05/02/22 01:47 AM

The question should be why are you using a 50 year old plate load. There is no reason to run 3000 pounds of plate load.
Posted By: hemienvy

Re: Thrust bearing wear with B&B clutch - 05/02/22 02:14 AM

Mad, the project I'm working on next little by little is a 430" big block that I want to be able to shift at 7000-7200.
I have read your posts and am impressed by your knowledge.
I'm inclined to keep these old clutches for, I don't know what, some mystery future use.
But realistically, for this particular deal, I will tell you, I'm planning a Richmond 6-speed with 3.54 rear gears.
I wonder if a Long plate with an organic disc might be the best compromise.
I say "street driven" but the car doesn't know if a 7200 RPM shift is street or race.
But it's not 9000 and it's not a 600 inch motor.
It can't be that hard a compromise...........
Posted By: Jeremiah

Re: Thrust bearing wear with B&B clutch - 05/02/22 11:29 AM

I run a Ram powergrip hd that is ~2900 lb b and b. It has sintered bronze on on side and iron on the other. Its a little barky below 2k, especially with some heat in it. So far the only breakage has been the clutch fork pivot folding over and ta trans side ballstud snapped off junk reproduction bb a body pivot bracket.

I would find a more modern clutch. Talk to somebody that has raced a srltick car recently and get direct experience. There is a lot of internet expertise around stick cars and carbs that is not backed up with results. Be cautious of regurgitated info is all i am saying.
Posted By: madscientist

Re: Thrust bearing wear with B&B clutch - 05/02/22 11:33 AM

Originally Posted by hemienvy
Mad, the project I'm working on next little by little is a 430" big block that I want to be able to shift at 7000-7200.
I have read your posts and am impressed by your knowledge.
I'm inclined to keep these old clutches for, I don't know what, some mystery future use.
But realistically, for this particular deal, I will tell you, I'm planning a Richmond 6-speed with 3.54 rear gears.
I wonder if a Long plate with an organic disc might be the best compromise.
I say "street driven" but the car doesn't know if a 7200 RPM shift is street or race.
But it's not 9000 and it's not a 600 inch motor.
It can't be that hard a compromise...........



Dont get me wrong. I have zero issues with the Borg & Beck plate. It’s fine. It’s all the base pressure. If the car is under 3800 pounds you can use an organic disc and you only need 2400 pounds of base pressure. 600 pounds may not seem like much but that’s quite a drop.

Years and years ago when I was still using that cover and I was at 3000 pounds of base I was having issues shifting above 6500ish. I fought it for a while and I was told the firewall was flexing, the linkage was flexing and all kinds of other stuff. I raised the fingers .100 and that made shifting quicker but it still wasn’t happy.

At any rate, I got on the phone with some Stock Eliminator guy I met in 1981 at a National event. I don’t even remember his name any more and not long after I met him he passed away. He was the one that told me all that stuff can flex and move but what you don’t see is the cover itself flexing. The way the levers are mounted to the cover and all that pressure makes the cover flex. When the cover flexes it makes the clutch drag because the plate doesn’t come off the disc evenly.

At that point to get the pressure down, we ended up running 9 springs. Of course, everyone was sure the clutch would explode without all 12 springs in there but it never happened. And it made shifting a blast. Plus, parts breakage went way down.

My car was light enough and had enough gear that I eventually got all the way down to 1800 pounds (that was only 6 springs) and it just got better. Of course, with bite you could get between 75 to maybe 100 passes on a disc before it had to be changed out.

Then I went to the soft lock and that’s even less plate load.

I would look at a good organic disc and taking some of that plate pressure out. If nothing else, your left leg and knee will thank you.
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