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Let's talk lighter weight clutches for LSX motors


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Working on limited knowledge a while back I purchased a Fidanza LS3 style recessed aluminum flywheel with the intention of running a LS7 pressure plate, disc and hydraulic throwout bearing.  Not so certain I want to go this route anymore.  The LS7 clutch/flywheel is 57lbs!  Jeese, that thing could get a tow truck rolling...  The LS7 flywheel is 26.5lbs and Fidanza is 13lbs so this nets a 13.5lbs reduction giving the Fidanza flywheel LS7 clutch a still porky 43.5lbs.  

 

Our S30 chassis cars with LS swaps are weighing in at between 2500-3000 lbs which really does not require a large mass flywheel/clutch package with large moment of inertia.  Seeing guys with racing flywheel/clutch weights ranging from 15-35lbs used in LSX motors around the web.

 

Now there are step type clutches and strap type.  Can anyone help me better understand the differences between these and how "drivability" suffers as one moves toward small diameter racing clutches?

 

 

Edited by 280Z-LS3
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I don't know what a step or strap clutch is, but I have a NASCAR style button clutch in mine. Flex plate for the starter and tiny clutch mating surface with two 7.25 disks. I think the flex plate and clutches came in around 20 lbs. I can tell you it revs and shifts fast. Carb isn't really dealing very well with it, so will probably go FI with it at some point. Needs an instantaneous huge squirt of fuel, but then needs to taper off fast, accelerator pump cams just aren't shaped right.

It's really grabby and wouldn't be fun in traffic, but I think it would probably be doable if necessary. They have carbon clutches that are better suited to driving on the street, but they're way more expensive and mine is a trailered race car, so I went this way.

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He already stated the reason; the stock flywheel and pp is 60 lbs. That's a big deal to me too. It's going to make the transmission significantly slower to shift, as well as just slowing the car down on accel, reduce engine braking, etc. I would like to drive one with a light flywheel and see how that is in actual driving. Might be good enough, even though it still sounds stupid heavy

Also should have pointed out the hassles with setting up a button clutch. You don't just slap it in. Need a special throwout bearing (more $$$) and have to take measurements from the bell housing and shim the bearing to the right depth, then limit the hydraulics so you don't push the bearing too far as you can pop the slave apart inside the bell housing or damage the pressure plate springs. It's not rocket science, but takes a little doing. I got my slave from QuarterMaster. https://www.quartermasterusa.com/qm/components/hydraulic-release-bearings-components/tri-lite-release-bearings-hydraulic-release-bearings-components 


I can't remember the reason, but my stock flex plate also wouldn't work with the button clutch, I had to buy an aftermarket one to put it all together (more $$$).

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In the situation of never driven a car with a race clutch so trying to access if the drawbacks of light clutch are enough of a concern to ditch the idea.  EFI tuning and throwing belts are issues that have solutions.  Want to go into this race clutch eyes wide open knowing what I am signing on for...

 

54 minutes ago, alainburon said:

I guess the biggest question is how are you going to use your car? I see you have drivability concerns which leads me to believe you want to drive the car on the street. If that's the case why do you want a race clutch?

 

This will not be a "grocery getter" by any means.  It will see street driving to and from track/autocross events and spirited canyon runs.

 

12 hours ago, JMortensen said:

I don't know what a step or strap clutch is

 

I think a button clutch is a "step type" and a "strap type" is the more conventional design I am most familiar with where the outer pressure plate housing is connected to the friction plate by straps.  I have read on forums that the strap type is a form of torque management, would like to learn more about that...

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26 minutes ago, JMortensen said:

Also should have pointed out the hassles with setting up a button clutch. You don't just slap it in. Need a special throwout bearing (more $$$) and have to take measurements from the bell housing and shim the bearing to the right depth, then limit the hydraulics so you don't push the bearing too far as you can pop the slave apart inside the bell housing or damage the pressure plate springs

 

I have some experience with setting up a hydraulic throwout bearing, installed a Tilton 6000 series on a Centerforce clutch in my Mustang.  Not hard, just detailed measurements need to be taken.

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If you're not driving in traffic and just going for canyons or to the track, what I have would be OK. The big problem with the multi-disk clutches is that they can overheat pretty easily. Stop and go will kill one, as will slipping it too much with the sintered iron clutch disks.

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Going to stay away from the metallic discs for sure.  Tilton has a 7.5" clutch with cerametallic discs designed for some slip and I suppose other manufactures have similar friction material designed for applications requiring more heat tolerance.

 

Correction, it's "stand type" clutch not "step type". 

 

 

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I sure understand your goal here.  I went with a Fidanza aluminum flwheel, which was fairly light (12# IIRC), but then used a Centerforce full sized clutch.  I was blown away by how heavy the clutch pressure plate assembly was...to the point that I was wondering why I even bothered with a lightweight flywheel.

 

I have another track car (not a Z) that uses a very lightweight racing clutch, and my use of that car is similar to your intended use.  It is doable, but also pretty easy to stall in traffic if I don't concentrate on it.  It is possible to slip it...a little....but overall it is pretty much binary...either "in" or "out".  I have been using it for almost 15 years so I have to say it has held up well.

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Called Tilton today.  Detailed my setup and intended use then discussed various options.  Heard it enough now that it's starting to sink in that metallic plate clutches like 5.5" and 7.5" are binary.  Jeff at Tilton tried to steer me to the ST-246 but that is around 40lbs with flywheel so didn't feel in hit the sweet spot.  He went on to say they have a 8.5" kit in development with beta kits arriving around February 2021.  It's basically a scaled down version of the ST-246 offered with organic and cerametallic disc options with a total weight of 25lbs.  That sounds like could be a winner for my application using the cerametallic discs.

 

 

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