318is to 325is conversion

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  • providence
    Advanced Member
    • Jul 2007
    • 154
    #1

    318is to 325is conversion

    I've been going through various threads about making a 318i into an m20 and it seems feasible.. this is my question: If I have a 325is donor for a 318is chassis, what am I switching over besides engine, drivetrain, ecu, gauges?
    Is the running gear identical or do I need to replace the rear subframe to work with the larger case diff from the 6 cyl? Is all of the 'is' package stuff the same?
    Tags: None
    • e30Matt
      R3V Elite
      • Dec 2003
      • 5077
      #2
      Subframes are the same, medium case diff will bolt straight into the 318. CVs are the same from what I recall.

      "See, we're adding a little something to this month's sales contest. As you all know, first prize is a Cadillac Eldorado. Anyone wanna see second prize? Second prize is a set of steak knives. Third prize is you're fired."

        Comment

        • kowalski
          E30 Mastermind
          • Jan 2005
          • 1791
          #3
          why would you do this? if your going to go to the trouble to switch motors at least put something good in it...

            Comment

            • providence
              Advanced Member
              • Jul 2007
              • 154
              #4
              This is a question of having a 318is clean shell and a 325is working drivetrain on hand, and not a lot of extra money to source a different engine. Really want to figure out what's different between the two chassis after you physically install the m20 drivetrain into the 318is?

                Comment

                • e30Matt
                  R3V Elite
                  • Dec 2003
                  • 5077
                  #5
                  Other than the engine/harness, cooling system, driveline, and the cluster, they're pretty much the same car as far as I know.

                  "See, we're adding a little something to this month's sales contest. As you all know, first prize is a Cadillac Eldorado. Anyone wanna see second prize? Second prize is a set of steak knives. Third prize is you're fired."

                    Comment

                    • LivingLegend06
                      E30 Mastermind
                      • Dec 2006
                      • 1604
                      #6
                      The diff is a straight swap, I put a medium case 4.10 lsd into my 318is with no problems(sort of). I expect the motor swap to be fairly straight forward, but cant say anything on it from personal experience.

                        Comment

                        • z31maniac
                          I waste 90% of my day here and all I got was this stupid title
                          • Dec 2007
                          • 17566
                          #7
                          Sell/part the 325 and turbo or JRSC on the 318.
                          Need parts now? Need them cheap? steve@blunttech.com
                          Chief Sales Officer, Midwest Division—Blunt Tech Industries

                          www.gutenparts.com
                          One stop shopping for NEW, USED and EURO PARTS!

                            Comment

                            • gjuu
                              Member
                              • Jan 2005
                              • 78
                              #8
                              Originally posted by providence
                              This is a question of having a 318is clean shell and a 325is working drivetrain on hand, and not a lot of extra money to source a different engine. Really want to figure out what's different between the two chassis after you physically install the m20 drivetrain into the 318is?
                              I have done this swap - put a 2.7 M20 into my 318is.

                              Engine/gearbox bolted straight in
                              Engine electrics plugged straight in
                              Use your 325 driveshaft
                              If using M42 radiator you need to shorten top radiator hose (I left the M42 radiator in as it has the built in overflow reservoir which looks tidier). Also need to modify the small diameter hose to go around the alternator - see blue circles


                              I used the 4 cylinder diff whilst I was running the engine in - to stop me thrashing it too much :)
                              But once engine was good to go I swapped to a medium case diff that bolted straight in.

                              It took me less than a day total time to remove the M42, clean the enginebay and put the M20 in by myself.

                              out with the old


                              in with the new


                              it was plug and play - ideal if you don't want too much down time.

                                Comment

                                • providence
                                  Advanced Member
                                  • Jul 2007
                                  • 154
                                  #9
                                  Thanks gjuu.. NICE install..

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