Input Shaft Center Bearing style clutch

If the clutch gets out of balance, in my opinion, it doesn't matter who's crank you have, on a Chrysler, it's going to take out the rear main. That's at least what I have seen in my experience, which unfortunately, I've seen way too many.

The rub plates help, but nowhere near as much as the pressure plate support bearing. The Crower 10.7 3 disc that everyone ran for years (without center support bearing) really had to be in mint condition, particularly the flywheel to live above 9800-9900. The dragsters didn't see near the problem with the smaller 10" clutches until the rpm exceeded 10,500, and even then, it wasn't as prevalent. Basically once the flywheel got any run out, it would pick on the rear main more and more. Trust me we tried every 'trick' in the book, oiling, drain backs, rub plates, solid, full round, drilled/opposed floaters, etc. The support bearing by far significantly reduced rear main damage in Chrysler rear main blocks (Miner Bros and some newer designs have Thrust rear mains).

Nearly every clutch manufacturer now offers a rear bearing support option. Some offer a retrofit option, others you have to buy a new pressure plate or hat assembly. They do behave quite a bit different, to the point some teams have opted to stay with a non bearing support design. What the bearing support does is significantly strengthen/stiffen the pressure plate assembly. Long story short the additional flex on the outer diameter of a non bearing support clutch provided more plate load with less counter weight. With that flex gone, it takes more counter weight to achieve the same plate load. In my experience a bearing support 10.7 Crower takes almost 2x the counterweight a non bearing support Crower 10.7 does.

I do want to clarify that the bearing support does not eliminate rear main problems. It still needs to be checked every run on a TAFC. (Pause now for the Pro Mod guys mind to explode LOL). I have seen a team switch to a bearing support clutch, see that it wasn't causing near the rear main problems, then go 7-8 runs without checking it and wonder why the crank was all coppered up. One thing we did before the bearing support to help the situation was try to keep a fresh upper and lower in the rear main. If you made a run or two on it and it looked serviceable, we would put it aside and put it in 1, 2 or 4 next time we checked all the mains.

 

The 2x on the counterweight is due to the difference in the finger and the fact you lose the flex clamping. As mentioned, the hat can flex more to clamp harder on the outside without the bearing support. 20-35 grams were pretty common with the old hat in TAFC, you will have to run 40-70 grams with the same static to achieve the same results.

We tried all of those rear main oiling, clearance tricks over the years. 99% of the time, the problem is behind the motorplate. I suspect two factors that are probably harder on TAFC is bumps with the solid chassis and tireshake. You can drive through shake and pedal with a TAFC that in many cases with a suspended car, you have to lift and call it done. Something else that probably helps is the trans being supported in a door car. I've wanted to try that for years in a TAFC, but been told it's a big no-no. I'm sure the U-joint in a suspended car helps make that possible.

For a while a scalloped, lightened Ti flywheel was the norm. The progression from that to a beefier, full round, non lightened flywheel has helped a bunch. I think much of the problem is the flywheel. I still tell customers you can't afford an aluminum flywheel with a Crower, or at least the older design, in a TAFC that is going to go 9500+. I have seen Crowers new full round aluminum flywheel live in a TAD with a 10" clutch, but have no experience with it in a 10.7 application. Leanders' aluminum flywheel lives, but it is much beefier, and benefits from the bearing support.