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

Jeff20B · 03-02-2008, 04:09 PM

Please offer your input to help me make some decisions, please.

'74 REPU mild ports with Atkins Camden 5" SC going on in a month
'78 GLC with 6 port 13B conversion going in soon
'81 FB with mild ported 12A (with plans for an NA 20B!!)

I have some parts here that I'd like to use. Tell me what you think:

I have two Racing Beat light steel flywheels (13 pounds)
One 8 pound super light steel flywheel (you can't get these new anymore) it weighs and drives about the same as aluminum, so think of it as an aluminum flywheel.

Various stock 215mm and 225mm clutch discs

One Street Strip 225mm pressure plate and one Street strip 215mm pressure plate plus various 215mm and 225mm stock pressure plates.

Ok, we know the more torque the engine produces, the larger the disc required. Or we can increase the clamping force of the pressure plate at the expense of your left leg and clutch hydraulics (or get a dual disc but that is $$$$). I have enough parts here so I won't need to buy anything. I just need help figuring out where each component should go.

The intended use of the vehicle is also important when choosing a clutch. The heavier the vehical, typically the stronger the clutch. For example the REPU came stock with a 225mm disc, but it had a funny step making it incompatible with any other model. I feel I should try to keep 225mm for the REPU if possible.

Jeff20B · 03-02-2008, 04:15 PM

Ok, you're probably thinking the 20B should automatically get the best 225mm components. I have, or just go with some T2 240mm stuff since it will have so much torque, and you'd be right. However I already have these parts and would rather give them a try before buying something that I might not actually need. The 20B is staying NA for now so I feel I can get away with 225mm especially in an FB chassis (especially in the slightly lighter S model).

Don't forget the REPU will be used for towing and will have a supercharger which adds plenty of torque. Plus the heavier weight of the vehical has me thinking it should get the best 225mm components.

Lastly the GLC is small and light. It can easily get away with 215mm components and stock duty. It is how3ever geared kind of tall (3.727) and is a four seater which will be expected to haul 4 people and groceries from time to time. This is where my confusion comes in.

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 · 04-15-2008, 01:39 PM

How about an update?

The GLC got a non clearanced RB light steel flywheel, low mile 225mm disc (about 8.5mm thickness), and the rusty low mile 215mm pressure plate (seen above). The new engine is in the car now and the friction point and pedal effort feels reasonable. I think this setup will last a long time and be reliable.

The FB is temporarily getting a street ported 13B and the 5" Camden. It too has a non clearanced RB light steel flywheel, but this time I had access to a worn but probably useable 225mm 'street strip' HD disc. It's worn down to 7.3mm! That's thin, but combined with the 215mm SS pressure plate, the spring fingers are reasonably flat. That means it should work for a while. Good thing because after I get a feel for power in the FB, the 13B's coming out and the 20B is going in - possibly with the same setup.

I can get away with a 215mm pressure plate in an FB chassis because it's lighter than the REPU. If something's gotta give under that much torque, I'd rather have it be the clutch, which will slip a little then grip rather than break the rear end or a u-joint, as is common amoung FB owners who use puck clutches.

I saved the 225mm compatible RB light steel flywheel with only about 30 miles on it, the lowest mileage disc (8.6-8.7mm thickness) and the new 225mm SS pressure plate for the REPU. It will go in with the new engine after the tranny gasket is changed.

Whizbang · 10-18-2008, 12:54 AM

musical clutch components. interesting game.

Jeff20B · 10-18-2008, 03:15 PM

Quite.

It's update time! My bro's red '84 FB got one of the RB flywheels, a 225mm HD disc and a centerforce 215mm pressure plate. The pedal effort is easy and apparently grips harder as RPMs rise. It's a new clutch disc that needs time to break in so I haven't tried to feel whether the pressure plate indeed grips harder as RPMs go up, or whether it's just a gimmick. The engine is a 12A so it doesn't necessarily need super grip anyway. It matches the character of the car nicely ie it has power steering, awesome brakes, comfortable seats, nice exhaust note. Basically nothing is extreme on this car, and I couldn't be happier with the way it turned out for him. Note there is a 5mm extra lip of clutch material that extends beyond the friction surface of the pressure plate. No problems.

The GLC is getting a new engine as the one I had built for it had the wrong apex side pieces (the little triangle things) from '74-'75 seals and get damaged tips from a little bit of missing chrome on the rotor housings. The engine will get rebuilt with excellent chrome rotor housings, new correct apex side pieces and an older RB light steel flywheel, already broken in 225mm stock disc and a stock 215mm pressure plate. Stock is more than adequate in this small, light car. Infact the pedal effort is greater in this car compared to a 1st gen 7 due to the pedal being shorter with less travel. Stock feels almost like street strip. I don't forsee any problems with having a 5mm lip as described above.

The blue FB got an old aluminum flywheel with a ferrous friction surface of 225mm but already worn by a 215mm disc. I had an old used 225mm HD disc (7.5mm thickness) and a 215mm street strip pressure plate. I tried this combination and it works quite well. The pdeal effort is high as the spring fingers in the diaphram are shorter than a comparable 225mm SS pressure plate, but thankfully the FB has a long clutch pedal so bumper to bumper driving is acceptable, although tiring. I would not want anything stronger, and thankfully, it is not required at this time. I have plans for increasing the power, as will be chronicled elsewhere on this site, but for now with a supercharger, I haven't noticed any slippage. Again there is a 5mm lip of disc that extends beyond the pressure plate. Everything seems fine.

There you have it. Several clutch jobs with a mismatch of 215mm and 225mm parts.

Jeff20B · 11-11-2008, 02:57 PM

The FB still seems to be doing ok.

For the GLC I've decided to try out a 215mm disc so the 225mm can go to a different project. I'll update this thread with the results after the engine is built and installed.

Whizbang · 11-11-2008, 04:32 PM

any chance you have some pictures of the GLC. i have been hoping to find one sometime locally.

Jeff20B · 11-17-2008, 01:52 PM

I can post pics of the GLC later. Turns out I have a fresh rebuilt 13B here already that needs to be broken-in in something. What better vehicle than the GLC, eh? This will give me a chance to test the 215mm disc because there are some questions about the springs in the sprung center. The disc material is like-new at 8.3mm thick (uncompressed) so it has tons of life left. Then after the engine is finished breaking in, I can pull it and check on the springs to see whether they loosened up or whatever.

03-02-2008, 04:09 PM	#1
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	Help me upgrade clutches in my REPU, rotary GLC and FB Please offer your input to help me make some decisions, please. '74 REPU mild ports with Atkins Camden 5" SC going on in a month '78 GLC with 6 port 13B conversion going in soon '81 FB with mild ported 12A (with plans for an NA 20B!!) I have some parts here that I'd like to use. Tell me what you think: I have two Racing Beat light steel flywheels (13 pounds) One 8 pound super light steel flywheel (you can't get these new anymore) it weighs and drives about the same as aluminum, so think of it as an aluminum flywheel. Various stock 215mm and 225mm clutch discs One Street Strip 225mm pressure plate and one Street strip 215mm pressure plate plus various 215mm and 225mm stock pressure plates. Ok, we know the more torque the engine produces, the larger the disc required. Or we can increase the clamping force of the pressure plate at the expense of your left leg and clutch hydraulics (or get a dual disc but that is $$$$). I have enough parts here so I won't need to buy anything. I just need help figuring out where each component should go. The intended use of the vehicle is also important when choosing a clutch. The heavier the vehical, typically the stronger the clutch. For example the REPU came stock with a 225mm disc, but it had a funny step making it incompatible with any other model. I feel I should try to keep 225mm for the REPU if possible.

03-02-2008, 04:15 PM	#2
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	Ok, you're probably thinking the 20B should automatically get the best 225mm components. I have, or just go with some T2 240mm stuff since it will have so much torque, and you'd be right. However I already have these parts and would rather give them a try before buying something that I might not actually need. The 20B is staying NA for now so I feel I can get away with 225mm especially in an FB chassis (especially in the slightly lighter S model). Don't forget the REPU will be used for towing and will have a supercharger which adds plenty of torque. Plus the heavier weight of the vehical has me thinking it should get the best 225mm components. Lastly the GLC is small and light. It can easily get away with 215mm components and stock duty. It is how3ever geared kind of tall (3.727) and is a four seater which will be expected to haul 4 people and groceries from time to time. This is where my confusion comes in. Last edited by Jeff20B; 03-02-2008 at 04:33 PM..

10-18-2008, 12:54 AM	#8
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	musical clutch components. interesting game. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

10-18-2008, 03:15 PM	#9
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	Quite. It's update time! My bro's red '84 FB got one of the RB flywheels, a 225mm HD disc and a centerforce 215mm pressure plate. The pedal effort is easy and apparently grips harder as RPMs rise. It's a new clutch disc that needs time to break in so I haven't tried to feel whether the pressure plate indeed grips harder as RPMs go up, or whether it's just a gimmick. The engine is a 12A so it doesn't necessarily need super grip anyway. It matches the character of the car nicely ie it has power steering, awesome brakes, comfortable seats, nice exhaust note. Basically nothing is extreme on this car, and I couldn't be happier with the way it turned out for him. Note there is a 5mm extra lip of clutch material that extends beyond the friction surface of the pressure plate. No problems. The GLC is getting a new engine as the one I had built for it had the wrong apex side pieces (the little triangle things) from '74-'75 seals and get damaged tips from a little bit of missing chrome on the rotor housings. The engine will get rebuilt with excellent chrome rotor housings, new correct apex side pieces and an older RB light steel flywheel, already broken in 225mm stock disc and a stock 215mm pressure plate. Stock is more than adequate in this small, light car. Infact the pedal effort is greater in this car compared to a 1st gen 7 due to the pedal being shorter with less travel. Stock feels almost like street strip. I don't forsee any problems with having a 5mm lip as described above. The blue FB got an old aluminum flywheel with a ferrous friction surface of 225mm but already worn by a 215mm disc. I had an old used 225mm HD disc (7.5mm thickness) and a 215mm street strip pressure plate. I tried this combination and it works quite well. The pdeal effort is high as the spring fingers in the diaphram are shorter than a comparable 225mm SS pressure plate, but thankfully the FB has a long clutch pedal so bumper to bumper driving is acceptable, although tiring. I would not want anything stronger, and thankfully, it is not required at this time. I have plans for increasing the power, as will be chronicled elsewhere on this site, but for now with a supercharger, I haven't noticed any slippage. Again there is a 5mm lip of disc that extends beyond the pressure plate. Everything seems fine. There you have it. Several clutch jobs with a mismatch of 215mm and 225mm parts. Last edited by Jeff20B; 11-14-2009 at 11:37 PM..

11-11-2008, 04:32 PM	#11
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	any chance you have some pictures of the GLC. i have been hoping to find one sometime locally. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

03-02-2008, 04:27 PM	#3
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	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	#4
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	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	#5
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	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	#6
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	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.

04-15-2008, 01:39 PM	#7
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	How about an update? The GLC got a non clearanced RB light steel flywheel, low mile 225mm disc (about 8.5mm thickness), and the rusty low mile 215mm pressure plate (seen above). The new engine is in the car now and the friction point and pedal effort feels reasonable. I think this setup will last a long time and be reliable. The FB is temporarily getting a street ported 13B and the 5" Camden. It too has a non clearanced RB light steel flywheel, but this time I had access to a worn but probably useable 225mm 'street strip' HD disc. It's worn down to 7.3mm! That's thin, but combined with the 215mm SS pressure plate, the spring fingers are reasonably flat. That means it should work for a while. Good thing because after I get a feel for power in the FB, the 13B's coming out and the 20B is going in - possibly with the same setup. I can get away with a 215mm pressure plate in an FB chassis because it's lighter than the REPU. If something's gotta give under that much torque, I'd rather have it be the clutch, which will slip a little then grip rather than break the rear end or a u-joint, as is common amoung FB owners who use puck clutches. I saved the 225mm compatible RB light steel flywheel with only about 30 miles on it, the lowest mileage disc (8.6-8.7mm thickness) and the new 225mm SS pressure plate for the REPU. It will go in with the new engine after the tranny gasket is changed.

11-11-2008, 02:57 PM	#10
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	The FB still seems to be doing ok. For the GLC I've decided to try out a 215mm disc so the 225mm can go to a different project. I'll update this thread with the results after the engine is built and installed.

11-17-2008, 01:52 PM	#12
Jeff20B Rotary Fanatic Join Date: Mar 2008 iTrader: (1) Posts: 215 Rep Power: 17	I can post pics of the GLC later. Turns out I have a fresh rebuilt 13B here already that needs to be broken-in in something. What better vehicle than the GLC, eh? This will give me a chance to test the 215mm disc because there are some questions about the springs in the sprung center. The disc material is like-new at 8.3mm thick (uncompressed) so it has tons of life left. Then after the engine is finished breaking in, I can pull it and check on the springs to see whether they loosened up or whatever.