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a bit of clarification on M20 flywheel/clutch conversion

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    #76
    The same small diameter bearing that is used with some of the g240s?

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      #77
      Yes. Only 2 sized BMW bearings AFAIK. Large and small diameters. I have 2 sized clutch tools, never saw an odd one to this day and I've work on these cars daily at my shop for several years.
      john@m20guru.com
      Links:
      Transaction feedback: Here, here and here. Thanks :D

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        #78
        Ok cool, 50-50 chance then haha. Thanks so much for all the information :)

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          #79
          Yep, it's 50/50. To save time you can get both pilot bearings. The last Sachs clutch kit I got had both clutch alignment tools in it, however the very first one I got didn't have both of them.

          Basically, have the parts, because it's really frustrating when you are trying to shove a transmission in place and it just won't go, and you've double checked everything (except the pilot bearing ID).

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            #80
            bump. any news or new findings in m42 clutch mod department?

            Got 1988 E30 m40, swaped m42 engine.
            Original gearbox, I suppose it's Getrag 240

            m20 flywheel (323i single mass one is what am really after as it's lightiest)
            m20 clutch, pressure plate (either from 323i or 325i)
            m20b23 throw out bearing
            m20 (ANY) FW bolts

            spacer taken of m42 FW
            m20 (late version??) starter (or a pinion gear to use on m42 starter - which is lighter and that's what im going to do i guess)

            once again. is that going to fit on my swapped engine? perhaps there are some news on this subject since the 2012 :)

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              #81
              Don't bother swapping pinions if you don't need to. M20 starter is nearly the same weight IIRC. Most any TOB will work, you don't need the M20B23 specifically.

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                #82
                Helpful bump!

                Am planning this out for my 91 318is atm.

                Found this while looking for M20/lightened flywheels. Basically all the benefits of the M20 swap, but it's lighter and you can keep M42 specific parts intact.

                So my plan is:
                RHD M42 flywheel (7lbs)
                FX racing stage 2 clutch
                M42/M20 tob 21 51 7 521 471
                M20b23/M20b25 flywheel bolts 11 22 7 805 885 (M12X1.5X28)
                Spacer from M42 if needed - I think because the fw is made for m42 I won't need it, but will test fit and see.
                M42 starter

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                  #83
                  Originally posted by nd4spd13 View Post
                  Helpful bump!

                  Spacer from M42 if needed - I think because the fw is made for m42 I won't need it, but will test fit and see.
                  M42 starter

                  You shouldn't need the spacer. The stock m20 FW has a protrusion on the back that interferes with the m42 and 24v rear main seal housing. The spacer was to move the FW further back to clear this.
                  john@m20guru.com
                  Links:
                  Transaction feedback: Here, here and here. Thanks :D

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                    #84
                    Originally posted by ForcedFirebird View Post
                    You shouldn't need the spacer. The stock m20 FW has a protrusion on the back that interferes with the m42 and 24v rear main seal housing. The spacer was to move the FW further back to clear this.
                    Agreed. Fingers crossed at least.

                    Will be piecing this together through December and Jan along with a replacement G240, so will report back when it's all ready to go in.

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                      #85
                      Hey all, first time posting and I know this thread hasn’t been touched in while. I am hoping that someone can help me.

                      I just converted my m42 to a m20 lightweight flywheel. Roughly around 5.6kg with minimal work done to take weight out of it. It currently has 325i clutch, pressure plate and a 323i TOB. I didn’t put the shim Plate in as my old m42flywheel was a single mass and didn’t have a shim plat. I also had no clearance issues with the m20 flywheel and back of the engine.

                      The issue I now have is free play in the clutch pedal, the first half of the pedal feels like it is doing no work other than moving the slave rod (I can easily push it down with my hand with no effort) the last half is when the clutch pedal gets hard and it feels like a clutch pedal with effort I can push it down.

                      The clutch has been bled. If I was to put the shim in behind my flywheel up against the crank would it bring my flywheel out and reduce the amount of free play I have in the pedal. Any help would be apricated and if you had this issue how did you end up fixing itHey all, first time posting and I know this thread hasn’t been touched in while. I am hoping that someone can help me.

                      I just converted my m42 to a m20 lightweight flywheel. Roughly around 5.6kg with minimal work done to take weight out of it. It currently has 325i clutch, pressure plate and a 323i TOB. I didn’t put the shim Plate in as my old m42flywheel was a single mass and didn’t have a shim plat. I also had no clearance issues with the m20 flywheel and back of the engine.

                      The issue I now have is free play in the clutch pedal, the first half of the pedal feels like it is doing no work other than moving the slave rod (I can easily push it down with my hand with no effort) the last half is when the clutch pedal gets hard and it feels like a clutch pedal with effort I can push it down.

                      The clutch has been bled. If I was to put the shim in behind my flywheel up against the crank would it bring my flywheel out and reduce the amount of free play I have in the pedal. Any help would be apricated and if you had this issue how did you end up fixing it

                      this is for a e30 318is 1990

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                        #86
                        I wouldn't expect the shim to be the main source of the issue, but it can clearly contribute. Sounds more like you still have air somewhere or have wear in one of the two cylinder bores. The latter does not apply if the issue wasn't present before.

                        Also, new or used clutch pivot pin and pressure plate?

                        Also, I think we debunked the need for a specific 323 TOB as the functional difference between that and the unit that is specified for a multitude of applications is unimportant.

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                          #87
                          Yeah, an M20 clutch/flywheel/PP/TOB is totally compatible with the M42. A stock M20 flywheel MIGHT have clearance issues, but lightweight ones usually have material removed such that it clears the oil pan. The only issue is the difference in starter ring pitch.

                          When you reinstalled the slave cylinder, did the plunger hit the pivot arm and provide plenty of resistance to installation? I'd also guess that you need to bleed things, or maybe they are worn, as roguetoaster suggested.

                          I generally feel like the top 30-40% of the clutch pedal travel does almost nothing in every E30 I have driven. It feels like the clutch is mostly engaged by around the mid-way point as far as I can tell. But, there is a healthy amount of pedal resistance at all points, so if it feels really soft/spongy at the top then there is an issue.

                          Transaction Feedback: LINK

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                            #88
                            Thankyou for your reply’s. I had my slave rebuilt when I was doing the conversion and it had a good amount of resistance when installing. I would say the top 40% is soft and spongy but has little to no resistance my old m42 clutch and flywheel had some free play Aswell but wasn’t as much.

                            ill give the car a bleed again this week and see if it resolves things or makes things better.

                            when you say that on most e30s you have driven do nothing in that 30%- 40% range.Where you able to push it down until it engaged with no effort?

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                              #89
                              Originally posted by Vandy688 View Post
                              Thankyou for your reply’s. I had my slave rebuilt when I was doing the conversion and it had a good amount of resistance when installing. I would say the top 40% is soft and spongy but has little to no resistance my old m42 clutch and flywheel had some free play Aswell but wasn’t as much.

                              ill give the car a bleed again this week and see if it resolves things or makes things better.

                              when you say that on most e30s you have driven do nothing in that 30%- 40% range.Where you able to push it down until it engaged with no effort?
                              On most E30s the pedal is very light for 20% of travel, and then it ramps up from there. Resistance should increase with travel if the hydraulic system is healthy.

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                                #90
                                Originally posted by Vandy688 View Post
                                Thankyou for your reply’s. I had my slave rebuilt when I was doing the conversion and it had a good amount of resistance when installing. I would say the top 40% is soft and spongy but has little to no resistance my old m42 clutch and flywheel had some free play Aswell but wasn’t as much.

                                ill give the car a bleed again this week and see if it resolves things or makes things better.

                                when you say that on most e30s you have driven do nothing in that 30%- 40% range.Where you able to push it down until it engaged with no effort?
                                The first 30-40% from the top feels like there is resistance, but until I get it to at least 30% down the clutch does not feel like it is disengaging. Similarly, if you have the pedal all the ay down, it feels like it won't start to grab until the pedal is 20% of the way back up. So really, 50% or more of the pedal travel is functionally useless lol. That has been my experience on most E30's anyway, including ones with fresh new clutch/PP/TOB parts.

                                I just had a thought. Did you make sure that the little black plastic clutch pivot pin was installed? I could see there being excessive play/dead zone if that was forgotten since the pivot arm would have to move further to do its job.

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