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| Flywheel/clutch problems https://www.ausmini.com/forums/viewtopic.php?f=5&t=67318 |
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| Author: | 69elf [ Sun Nov 28, 2010 3:49 pm ] |
| Post subject: | Flywheel/clutch problems |
We made good progress assembling the engine yesterday until we got to the putting on the clutch end cover (wok). We' re using a minispares ligthened flywheel (with the spacers that came with it), a minispares lightened back plate, 3 driving straps and a grey dot diaphragm. We're also using a minispares heavy duty clutch arm. The clutch housing and wok are both the original items that were on the 1275 A+ engine (it's an early pre verto A+) when we stripped it down for the rebuild and since the clutch release bearing all appeared to be OK I took it off the original clutch plunger and put it on the new clutch plunger (the plungers are both exactly the same length. The only difference is the hole machined in them for the arm) that came with the heavy duty arm. However when we bolt every thing together there is absolutely no movement on the clutch arm and plunger and the actuating push rod in the slave cylinder is pushed right to the back of the cylinder ie the arm just can't move. We've taken lots of measurements eg from the ring gear to the lip of the clutch housing and compared them to the original 998 engine which came out came out of the car and all measurements between the new engine and the old engine ae the same which indicates that the flywheel etc is bolted in OK. In the instruction sheet that came with the flywheel it says if you are using more than the standard two driving straps that you have to mill that thickness of the flywheel spacers and the horns of the back plate. But would that really make that much difference? Would the the thickness of less than 1mm (or whatever a driving strap thickness is) result in no movement of the actuating plunger/release bearing where we were looking for at least 5mm? Or is something else wrong? If it is the extra driving strap then the next question is do I really need 3 straps? The engine is a 1430 with a supercharger, SW5 cam, Graham Russel head (flowed at 133cfm), etc. I expect around 130+hp but it is just a road engine. Any advice would be much appreciated. |
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| Author: | drmini in aust [ Sun Nov 28, 2010 9:28 pm ] |
| Post subject: | |
The drive straps are about .035" thick. Putting an extra one in reduces the assembled height of the diaphragm spring, and hence its clamping load. It's not just a question of release bearing position. The spring should be flat (parallel to the flywheel) when assembled with a NEW clutch plate. This is most important with big torquey NA motors or turbo ones. I assemble the clutch on the bench then use a 1/8" drill bit held against the spring, and a torch, to check this. Often with old worn/machined flywheels and backplates they are miles out- one I did recently needed .070" off the 3 backplate lugs to make it correct. If you've not done so already I suggest you read Marcel Chichak's story on how to correctly set up a Mini clutch. http://www.minimania.com/web/DisplayID/ ... ticleV.cfm BTW my 1360 roady has somewhere near 130HP at crank, it runs just fine with 2 straps, an orange diaphragm and standard AP clutch plate. Ditto my 1412 stroker, with 112 ft/lb torque. |
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| Author: | 69elf [ Wed Dec 01, 2010 9:04 am ] |
| Post subject: | |
Thanks Kevin for your suggestions and comments. It looks to me that the problem is caused by the spring on the diaphragm not sitting completely flat against the flywheel. I've decided against the grey diaphragm and have ordered an orange one so once that arrives, if the spring is still not sitting completely flat I'll take it all off to a machine shop to have metal machined off the back plate lugs to bring it completely flat. Thanks once again for the help |
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