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water pump belt too long?

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    water pump belt too long?

    Ok I started to reinstall the belts today on my budget 2.7i but with the Alternator tensioned as tight as it will go the belt driving the alternator and water pump is way to loose. I can easly spint he water pump by hand. I checked the belt and sure enough its 965mm like it should be and thats what the etk shows for both an eta and an I. Any ideas? I noticed the 318i m10 belt is 100mm shorter so I may buy one of those and give it a shot. This makes no sense as the alternator is the same one on the engine, as well as the water pump pulley. But the harmonic balance is the toothed I variant.
    85 325e 2.7 ITB'd stroker

    #2
    ok figured it out the 325i uses a different water pump pulley and I've currently have a 325e one mounted on it. The thing that sucks is I don't have any around, I just called a bmw repair shop somewhat near by and they've got one.
    85 325e 2.7 ITB'd stroker

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      #3
      I never thought I would see the day that Ely would post a question about installing a v-belt on an M20.

      Comment


        #4
        Originally posted by Ritalin Kid
        I never thought I would see the day that Ely would post a question about installing a v-belt on an M20.
        lol,

        yeah me neither. it's a legit mistake; he wanted a quick answer.

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          #5
          Originally posted by X2theZ3
          lol,

          yeah me neither. it's a legit mistake; he wanted a quick answer.
          Heresay.. it's a sign of the end times

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            #6
            Yes, I have done two of these swaps now and both times the belts havent worked. From what I hear the pullies are underdriven from an eta to an i. I used a different belt. If you want to go that route I can give you the length you need.
            Old and improved:

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              #7
              Sometimes you can measure out what you need or grab your existing belt and take it to Autozone or Advanced and they can find a close fit. If you take your existing belt just tell them you need one a few inches shorter.

              My best friend's father in law has done this a few times with no problems.

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                #8
                Parts stores don't have specific to your vehicle belts. They just have belts of various lengths, then they look up the size for your car and give you the correct length one.

                My point by all this is that all you need to know is the belt length and you can get any belt you want.

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                  #9
                  Originally posted by NitroRustlerDriver
                  Parts stores don't have specific to your vehicle belts. They just have belts of various lengths, then they look up the size for your car and give you the correct length one.

                  My point by all this is that all you need to know is the belt length and you can get any belt you want.
                  correcto.. went through this with my friend's m50 swap. You'd be suprised how many parts guys dont know that those numbers on the belt indicate size.
                  Old and improved:

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                    #10
                    lol
                    Any ways got the 325i pulley from a somewhat local mechanic and sure enough pops right on, belt problem fixed. I went threw the same thing with my m30 as I had the a mixture of e30, e28, and e34 belts on it.
                    85 325e 2.7 ITB'd stroker

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                      #11
                      I need to put a belt on mine but... i'm not sure what i have.
                      I do have the eta vibe-damper and distance between pullies is ~3mm.
                      So since an i water pulley wouldnt fit, then i'm pretty sure i have the full eta setup.
                      But this would mean that the i water pump runs slower, proportionally to rpm... hmm, due to the fact an eta runs at lower rpm?
                      I wonder if this kind of thing would provide better cooling capabilities?
                      eta is 105mm/170mm. can some one measure the outer diameters of the i wp/crank pullies?

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                        #12
                        Well if the longer belt requires an "i" pulley to fit correctly it's only correct to assume that the "e" pulley is smaller.

                        I would also assume that if you were to swap an "e" pulley unto an "i" pulley that you would get more rotations per motor RPM. Though I don't think you would see a huge different until you got past 5000RPM in terms of colling performance.

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                          #13
                          ya the belt lengths betweent he two engines is the same, and the alternator pulley is the same size. But the I's have a smaller crank pulley and bigger w-pump pulley then the eta.
                          85 325e 2.7 ITB'd stroker

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                            #14
                            ritalin kid, going from e to i w/p pullies would be a decrease in speed.
                            besides, the i probably wont fit next to the e crank pulley due to size.
                            if we could get the i pulley sizes, we could figure up the water movement ratio.

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                              #15
                              Originally posted by xLibelle
                              ritalin kid, going from e to i w/p pullies would be a decrease in speed.
                              besides, the i probably wont fit next to the e crank pulley due to size.
                              if we could get the i pulley sizes, we could figure up the water movement ratio.
                              That's what said only you said it backwards.. I said going from "i" to "e" pulley would make the w/p rotate faster.

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