Help me upgrade clutches in my REPU, rotary GLC and FB

Jeff20B · 03-02-2008, 04:27 PM

My REPUis currently NA and has the stock 30 pound flywheel with its 225mm disc and pressure plate and it has plenty of grip. By itself, the current setup feels a little on the heavy side. When towing it feels fine. When it gets an SC, the additional rotating weight of the roots blower 'peanuts' add a noticeable amount of extra weight to the rotating assembly. You can feel it when you drive.

Think of it like this: as a general rule, you always want to chose a flywheel one step lighter than you ordinarily would. In other words if you absolutely love the feel of a Racing Beat light steel flywheel in NA form, and countless rotorheads do, you will definetly want to switch to an aluminum flywheel when getting an SC. The extra spinning weight of the SC makes the aluminum flywheel feel a lot like a 13 pound light steel.

Same is true for let's say a GSL-SE flywheel, which weighs about 27 pounds. This flywheel was an upgrade from the stock 215mm 30 pound flywheel in my bro's RX-4 wagon. The old 30 pounder felt heavy. The GSL-SE was a major improvement but we could tell that a light steel would have been too light due to the tall diff gearing of 3.636 and weight of the wagon. We should have gone ahead with it though because he got an SC and once it was on there it felt just like the old heavy clunker 30 pound flywheel and made the car actually less fun to drive than it was in NA form. Strange to tell.

The SC is coming off the wagon and going on the REPU. This is why I need to upgrade the flywheel and chose a good disc and pressure plate combo that will handle the torque and the weight of the truck as well as slippage during towing while starting from a stop etc.

Jeff20B · 03-02-2008, 04:33 PM

Next we have the FB.

The nice 12A that's going into the FB is currently in PercentSevenC's '83 GSL. It is a very nice setup consisting of the 8 pound superlight flywheel, stock 215mm disc and a 215mm street strip pressure plate.

The pedal effort is perfect. Not to hard, not to soft. The stock style disc is plenty strong enough to handle whatever he's thrown at it. No slippage. Burnouts are possible even with an 8 pound flywheel. Acceleration in the lower gears is wonderful, but you can tell the engine lacks some torque in the higher gears compared to the 13Bs I'm used to.

Ok, now that's we've established that this setup works and works well, I wonder if it is going to be adequate with twice the torque from the 20B.

Hmm...

Jeff20B · 03-02-2008, 04:42 PM

Sorry if you're totally confused at this point. I have a golden opportunity here to take adavantage of several parts that suddenly became available, and I'd like to make some good decisions and use the best parts for the intended uses of the vehicles described above.

What I'm mainly wondering is whether the 20B could get away with the superlight flywheel and 215mm components in the light FB chassis, or will the mamouth torque require me to use 225mm components even though it means having to use heavier parts with more inertia.

I also must try to keep the clutch assembly light in the truck since the SC will add back the rotating weight making towing a little easier and all that. But it should also probably stay 225mm since that is what it came with stock.

The GLC is the only vehicle that can get away with 215mm. The current setup feels a little heavy consisting of RB 13 pound flywheel, 225mm disc and pressure plate. Simply keeping the flywheel and dropping the disc and pressure plate down to 215mm would take care of it. No need to swap flywheels to the 8 pounder since the car will be used for moving people and groceries.

Jeff20B · 03-02-2008, 04:53 PM

So rather than keep beating a dead horse, I'll come right out and ask the question:

Can a 20B get away with a 215mm clutch disc?

Short answer NO unless you increase the pressure plate in some way, such as with the street strip one I described above. But this is only a maybe.

I just love the way it drives though in Percent's FB. It's light, responsive, has plenty of grip. It would allow the 225mm street strip pressure plate to be used in the REPU where it honestly is needed more. Heck my friend's '77 REPU has a 7" SC with a Racing Beat light steel flywheel, HD disc and 225mm pressure plate and it tows very well and has done so since we swapped it in there several years ago. The only difference here is mine would use a stock disc since I don't like a super short friction point (the shorter pedal travel of the REPU makes the friction point shorter than an FB using identical components).

So if the 215mm street strip will work in the FB with the 20B, I'll go for it saving the 225mm stuff for the REPU.

Oh, and since the 20B needs a rebuild, I can definitely use the 215mm stuff during break in.

If it starts to slip I can always look for an aluminum Fidanza or something.

Jeff20B · 03-02-2008, 05:04 PM

The other option I'm looking on the REPU is a 225mm disc, but a 215mm pressure plate!! It is possible. The reason I mention it is because early RB light steel flywheels were never clearanced along the upper lip making it not a good idea to use a 225mm pressure plate as the rivits contact the lip bit 215mm have plenty of clearance.

So here we see a non clearanced RB light steel flywheel.

225mm disc

stock rusty 215mm pressure plate

installed

5mm gap

Total grip is of course less than a complete 225mm setup, but still more than a complete 215mm setup. Let's call it 220mm.

This is an option available to me and would probably work well in the REPU.

What do you guiys think? I think the lighter intertia of a 215mm pressure plate would be ideal in the REPU with a supercharger, and the extra holding capacity of the street strip pressure plate would make up for the slightly reduced friction surface. Plus the disc itself will still have 225mm of grip against the flywheel surface.

I will go ahead with this idea if it is recommended to use full 225mm components with the 20B. Besides, the last time the 20B ran, it had full 225mm stuff, and it *blipped very nicely.

* blipped is like "tip in" when you blip the throttle and the car lurches forward. In other words the higher intertia of the 225mm components did not feel heavy. Even with the extra rotating weight of a 3rd rotor, it did not feel heavy. A 12A with the same 225mm stuff feels heavy by comparison. Hence the reasoning earlier about wanting to use the super light 8 pound flywheel with the 12A in the FB and continuing to use it with the 20B even though it might cause slipage or possibly break the clutch lining from the springy marcels or some other catastrophic failure. It would work fine during break in, but probably wouldn't stand up to the torque for very long after.

Jeff20B · 03-02-2008, 05:30 PM

Ah screw it.

Why don't I do this:

REPU: unclearanced RB flywheel, 225mm disc, 215mm SS pressure plate.
FB: clearanced RB flywheel, 225mm disc, 225mm SS pressure plate.
GLC: super light flywheel, 215mm disc, 215mm stock pressure plate (heavy 8.5 pound)

The REPU will end up with probably about the same amount of total clutch grip as a stock setup, which I've always found to be adequate. Possibly even greater than stock, actually. I won't have to buy anything.

The FB will get full 225mm stuff, and will feel heavy with the 12A, but I also wanted to learn how to do J-turns, doughnuts (donuts?) and other fun parking lot maneuvers. Then when the 20B goes in it will feel just right and actually hold the torque for a while, even after break in.

And finally the GLC will get the super light flywheel because that is all that's left. It's only compatible with 215mm clutch components but that's ok. The GLC doesn't need anything bigger.

Hmm, it might actually be possible to use a 225mm pressure plate if I use the RB long bolt kit. The flywheel lip has three small clearanced cutouts. I'll know more once I have access to it. Otherwise it will get the heavy 215mm pressure plate I've had kicking around here for a long time. Most pressure plates weigh 8 pounds. This one weighs 8.5 pounds. It's not a lot, but hauling four people and groceries makes you think twice about some things.

Jeff20B · 03-02-2008, 05:48 PM

Here is a the super light flywheel. It only weighs 8 pounds.

Here are the two RB light steel flywheels. The one on the left is clearanced for 225mm pressure plate use. The one on the right only works with 215mm pressure plates.

03-02-2008, 04:27 PM	#1
Jeff20B Rotary Fanatic Join Date: Mar 2008 Posts: 215 Rep Power: 18	My REPUis currently NA and has the stock 30 pound flywheel with its 225mm disc and pressure plate and it has plenty of grip. By itself, the current setup feels a little on the heavy side. When towing it feels fine. When it gets an SC, the additional rotating weight of the roots blower 'peanuts' add a noticeable amount of extra weight to the rotating assembly. You can feel it when you drive. Think of it like this: as a general rule, you always want to chose a flywheel one step lighter than you ordinarily would. In other words if you absolutely love the feel of a Racing Beat light steel flywheel in NA form, and countless rotorheads do, you will definetly want to switch to an aluminum flywheel when getting an SC. The extra spinning weight of the SC makes the aluminum flywheel feel a lot like a 13 pound light steel. Same is true for let's say a GSL-SE flywheel, which weighs about 27 pounds. This flywheel was an upgrade from the stock 215mm 30 pound flywheel in my bro's RX-4 wagon. The old 30 pounder felt heavy. The GSL-SE was a major improvement but we could tell that a light steel would have been too light due to the tall diff gearing of 3.636 and weight of the wagon. We should have gone ahead with it though because he got an SC and once it was on there it felt just like the old heavy clunker 30 pound flywheel and made the car actually less fun to drive than it was in NA form. Strange to tell. The SC is coming off the wagon and going on the REPU. This is why I need to upgrade the flywheel and chose a good disc and pressure plate combo that will handle the torque and the weight of the truck as well as slippage during towing while starting from a stop etc.

03-02-2008, 04:33 PM	#2
Jeff20B Rotary Fanatic Join Date: Mar 2008 Posts: 215 Rep Power: 18	Next we have the FB. The nice 12A that's going into the FB is currently in PercentSevenC's '83 GSL. It is a very nice setup consisting of the 8 pound superlight flywheel, stock 215mm disc and a 215mm street strip pressure plate. The pedal effort is perfect. Not to hard, not to soft. The stock style disc is plenty strong enough to handle whatever he's thrown at it. No slippage. Burnouts are possible even with an 8 pound flywheel. Acceleration in the lower gears is wonderful, but you can tell the engine lacks some torque in the higher gears compared to the 13Bs I'm used to. Ok, now that's we've established that this setup works and works well, I wonder if it is going to be adequate with twice the torque from the 20B. Hmm...

03-02-2008, 04:42 PM	#3
Jeff20B Rotary Fanatic Join Date: Mar 2008 Posts: 215 Rep Power: 18	Sorry if you're totally confused at this point. I have a golden opportunity here to take adavantage of several parts that suddenly became available, and I'd like to make some good decisions and use the best parts for the intended uses of the vehicles described above. What I'm mainly wondering is whether the 20B could get away with the superlight flywheel and 215mm components in the light FB chassis, or will the mamouth torque require me to use 225mm components even though it means having to use heavier parts with more inertia. I also must try to keep the clutch assembly light in the truck since the SC will add back the rotating weight making towing a little easier and all that. But it should also probably stay 225mm since that is what it came with stock. The GLC is the only vehicle that can get away with 215mm. The current setup feels a little heavy consisting of RB 13 pound flywheel, 225mm disc and pressure plate. Simply keeping the flywheel and dropping the disc and pressure plate down to 215mm would take care of it. No need to swap flywheels to the 8 pounder since the car will be used for moving people and groceries.

03-02-2008, 04:53 PM	#4
Jeff20B Rotary Fanatic Join Date: Mar 2008 Posts: 215 Rep Power: 18	So rather than keep beating a dead horse, I'll come right out and ask the question: Can a 20B get away with a 215mm clutch disc? Short answer NO unless you increase the pressure plate in some way, such as with the street strip one I described above. But this is only a maybe. I just love the way it drives though in Percent's FB. It's light, responsive, has plenty of grip. It would allow the 225mm street strip pressure plate to be used in the REPU where it honestly is needed more. Heck my friend's '77 REPU has a 7" SC with a Racing Beat light steel flywheel, HD disc and 225mm pressure plate and it tows very well and has done so since we swapped it in there several years ago. The only difference here is mine would use a stock disc since I don't like a super short friction point (the shorter pedal travel of the REPU makes the friction point shorter than an FB using identical components). So if the 215mm street strip will work in the FB with the 20B, I'll go for it saving the 225mm stuff for the REPU. Oh, and since the 20B needs a rebuild, I can definitely use the 215mm stuff during break in. If it starts to slip I can always look for an aluminum Fidanza or something.

03-02-2008, 05:30 PM	#6
Jeff20B Rotary Fanatic Join Date: Mar 2008 Posts: 215 Rep Power: 18	Ah screw it. Why don't I do this: REPU: unclearanced RB flywheel, 225mm disc, 215mm SS pressure plate. FB: clearanced RB flywheel, 225mm disc, 225mm SS pressure plate. GLC: super light flywheel, 215mm disc, 215mm stock pressure plate (heavy 8.5 pound) The REPU will end up with probably about the same amount of total clutch grip as a stock setup, which I've always found to be adequate. Possibly even greater than stock, actually. I won't have to buy anything. The FB will get full 225mm stuff, and will feel heavy with the 12A, but I also wanted to learn how to do J-turns, doughnuts (donuts?) and other fun parking lot maneuvers. Then when the 20B goes in it will feel just right and actually hold the torque for a while, even after break in. And finally the GLC will get the super light flywheel because that is all that's left. It's only compatible with 215mm clutch components but that's ok. The GLC doesn't need anything bigger. Hmm, it might actually be possible to use a 225mm pressure plate if I use the RB long bolt kit. The flywheel lip has three small clearanced cutouts. I'll know more once I have access to it. Otherwise it will get the heavy 215mm pressure plate I've had kicking around here for a long time. Most pressure plates weigh 8 pounds. This one weighs 8.5 pounds. It's not a lot, but hauling four people and groceries makes you think twice about some things.