Input Shaft Center Bearing style clutch

Discussion in 'PSI Superchargers Tech Questions' started by frank70, Mar 17, 2020.

  1. frank70

    frank70 NOSTALGIA DRAGSTER

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    We are new to this deal and having rear main issues on a BAE block at 10,000+ RPM.
    I know some guys are using the rubbing blocks on the blacknof the flywheel to help this issue, but I have heard that the center bearing support on the clutch hat that holds the input is a better fix, any thoughts or real world experience between the two options?
     
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  2. jay70cuda

    jay70cuda Active Member

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    What clutch and who's crank. We've never had a issue. Went from 11in aft 2 disc to Leander's 3 disc. Never had a issue. Bryant cranks never seemed to flex much. But I've seen other cranks flex and do what your seeing. I also have 2 center support throw out bearings if you wanna give it a try. Thanks jay
     
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  3. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    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.
     
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  4. jay70cuda

    jay70cuda Active Member

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    Will I'm curious as to why it takes twice as much counter weight? Also I know some guys add auxiliary oil feed line to the rear main or even line bore the rear main .001 larger to allow more oil around the crank. Why question is why? And why do some blocks seem to oil the rear main better than others? I ran a clutch for years, shifted at 9900 every lap. Looked at the mains every other race. The only time I ever had a issue was when the crank was repaired and not nitrated again. Ate bearings like it was it's job.
     
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  5. frank70

    frank70 NOSTALGIA DRAGSTER

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    Intresting feed back thanks guys. I will see if my cover plate can be modified, sounds like it would help.
    10” 3 disk Croewerglide clutch, Bryant crank, nostalgia nitro application sees 10,200 in the lights!
     
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  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    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.
     
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  7. rb0804

    rb0804 Active Member

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    The Crower center support clutch uses a different lever than a non center support clutch. They had to put a weird radius on it to make it all work and it transition from a positive to negative plane, or something to that effect. It makes them kind of weird and they do weird things and in my personal experience, along with talking to people in the alky ranks about the 10” unit it what worked with your clutch program don’t work with this lever. Doesn’t work any better or worse, just different.

    The Leander’s has square lugs for the floater as well as a center support built in.

    The Boninfante unit can uses a standard type lever, but their deal is kind of weird, it can be retro’d In but you need a special throwout bearing, possibly the throwout bearing collar.

    I second what Will says about the flywheel. Seems that the larger, beefier, heavier, non scalloped flyweel seems to be the biggest factor in extending the life of the rear main. We have run the Chrysler style rear main and the Chevy style
    Rear main. If your having a clutch out of balance issue, it will eat either one. Running a floater with 6 full lugs, vs. a floater with 3 full and 3 half lugs seem to make a difference and makes the pack less likely to rack on decel.

    Hope that helps some.
     
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