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  • random engine question: solid lifters

    Just curious, I know our engine has solid lifters and that is one of the things that makes it loud. But what exactly are lifters, specifically solid ones. From what I know...the only "lifter" is the spring? You have the cam pushing the valve down and the spring lifting it up. Could anyone explain how a lifter fits into this?! Also I know the M52 engine has hydrolic lifters and that is why the valves don't need to be adjusted...does this mean they have no valve springs?

    Thanks a lot...hope my question isn't too stupid. haha
    "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

  • #2
    On the S14 the "lifter" is also referred to as the valve shim bucket.

    Basically, the cam does not act "directly" on the valve. There is a upside-down-bucket shaped piece of metal that goes over the valve stem and is a precise fit into the lifter bore in the cam carrier. On the top of this piece is a small recess where the valve shims go. The shims are hardened smooth disc shaped pieces of metal (like a large coin) that come in different thicknesses. This is the piece the cam actually operates on to push the valve buckets and valves open. The shims come in different thicknesses, and that is how you adjust your valve "clearance", the distance from the cam base circle to the top of the shim.

    "Shim under bucket" lifters are different as the name implies. The cam acts directly on the bucket and the shim goes between the bucket and the valve.

    The purely mechanical nature of the valve actuation on the S14 is partly what makes the engines noisey. All the modern BMW engines have hydraulic lifters where the vavles are moved by fluid transfer. The advantage there is that they are self adjusting and quieter. They still use valve springs.

    HTH
    Last edited by Ironhead; 02-17-2004, 02:11 AM.

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    • #3
      Awesome, thanks a lot! I visually knew this piece existed but didn't know it was imortant enought to have a name and didn't know there could be different kinds.
      "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

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      • #4
        I'd like to extend that question if possible?
        Shim under bucket seems to be what a lot of people desire for high output/high revving motors.

        Is this a factor of valvetrain security? ie: shim wont "pop/fly" out under high stress(reving)?

        Is there another benefit to S.U.B setups?

        Sorry if this is a repeat question!!
        Chris
        Chris L.

        Spray paint and tire shine doesn't equate to a "restoration!"

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        • #5
          Originally posted by UNHCLL

          Is there another benefit to S.U.B setups?

          Sorry if this is a repeat question!!
          Chris
          Yes -- valvetrain weight. With shim-under setups, you're not moving around that big heavy shim -- you're running a much smaller diameter (and lighter) lash-cap-like shim under the bucket. A sample of two brand-new BMW standard shims yields the following weights:

          3.00 mm = 20.0 g
          4.25 mm = 28.3 g

          Conservatively, 90% of that weight will be removed from the valvetrain *just* by going to the shim-under setup.

          Why do you want a light valvetrain? So you can rev higher before valve float! Yes, there are other factors involved. Consider a "stockish" intake valve setup of about 160g (depends on your spring retaininer). If you drop 20g off that weight, you've moved your valve-float RPM limit from 8200 to about 8750 (for example -- there are other factors involved). Now, then, you need to have a setup which will make power there :-).
          Jefrem Iwaniw

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          • #6
            Originally posted by jefrem
            Yes -- valvetrain weight. With shim-under setups, you're not moving around that big heavy shim -- you're running a much smaller diameter (and lighter) lash-cap-like shim under the bucket. A sample of two brand-new BMW standard shims yields the following weights:

            3.00 mm = 20.0 g
            4.25 mm = 28.3 g

            Conservatively, 90% of that weight will be removed from the valvetrain *just* by going to the shim-under setup.

            Why do you want a light valvetrain? So you can rev higher before valve float! Yes, there are other factors involved. Consider a "stockish" intake valve setup of about 160g (depends on your spring retaininer). If you drop 20g off that weight, you've moved your valve-float RPM limit from 8200 to about 8750 (for example -- there are other factors involved). Now, then, you need to have a setup which will make power there :-).
            Is the shim now under as the description implies? Wouldn't there still be the same weight? If not what is used to "shim" different clearances for valve lash?

            T

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            • #7
              Originally posted by HANDBLT
              Is the shim now under as the description implies? Wouldn't there still be the same weight? If not what is used to "shim" different clearances for valve lash?

              T
              Yes, there is still a shim, but its *much* smaller. There are a couple of different ways of doing it, but typically you have variable thickness lash caps that fit on top of the valve stem directly. That's where the weight savings comes from.
              Jefrem Iwaniw

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              • #8
                Originally posted by jefrem
                Yes, there is still a shim, but its *much* smaller. There are a couple of different ways of doing it, but typically you have variable thickness lash caps that fit on top of the valve stem directly. That's where the weight savings comes from.
                Cool. That MUST be a pain in the ass with turner gears.

                T

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                • #9
                  Excellent descriptions from both guys!
                  When I still had bikes, the engines with shim under bucket had much longer intervals between checks. My ZXR400 engine (shim on top of bucket) needed the shims done every 6000 miles (usually 3 or 4 needed done)
                  With my chums FZ600 (can't remember which model) but with shims under bucket, the check interval was about 30000 miles!

                  So not only do you reduce mass, but you also reduce service intervals.

                  I'm in the middle of doing the shims on an old Lotus Esprit S3 engine which has shims under buckets. It's a real PITA as you have to remove the complete cam carrier to get to the shims, and some stick on the valves, and some stick in the buckets and some fall out when you remove the carrier.

                  At least doing the M3 was straight forward (after spending around 3 hours fabricating a tool)

                  By the way, I always go for minimum gap when doing shims - what's the general consensus on this - my thinking is you get maximum valve lift at the expense of more frequent shim adjustments. Is going for the middle of the range more sensible?

                  Steve
                  Steve
                  Steve
                  Scottish Cecotto

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                  • #10
                    just out of curiousity, how much does the S.U.B. modification usually cost? if your stock setup requires servicing, does it make sense to do the modification then to save on labour time/cost?



                    looks better than it runs :/

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                    • #11
                      I know the BMW motorsport shim under bucket setup is very expensive, well over $1K just in parts.

                      There are other drawbacks to it. For one, you need to pull the cams out in order to adjust valve clearance, then put it all back in to check your work. You better get it right the first time!

                      Also, I don't know how "available" the shims are when you need to do an adjustment. I imagine you can get them, but might not be easy.

                      On the S14 at least, I can't see any reason why the shim under bucket setup would need to be adjusted any less frequently than the standard setup.

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                      • #12
                        Would it then mean that as you are moving less weight around,you should be able to run softer springs, less inertia ?
                        Jon

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                        • #13
                          Can anyone post a picture of the shim under bucket setup...it would be very helpful...John you must have that in your pic archives, haha.
                          "It is needless to say that self-propelling vehicles, like other machines, will never do as much for one who does not understand them as for one who does."

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                          • #14
                            Here is a pic of a flat-top shim under bucket tappet (Schrick) next to a stock one with a shim on top:

                            http://www.bayareamotorsport.com/~jj...n/DSCN2298.JPG

                            Valve adjustments are much more of a pain b/c you do have to pull the cams out. You will WANT the turner cam gears so that you dont have to retime your cams! They will re-insert at the exact same timing, the BMW motorsport ones will require you to check your timing again.

                            The valve lash caps are way more expensive. That is the big draw back. They are like somewhere between $3-6 per cap. I think the BMW ones are even more expensive.
                            Jeff J.
                            1990 E30 M3

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                            • #15
                              wow alright, no point unless you need it for your engine setup. thanks guys.



                              looks better than it runs :/

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