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My 2.7i Build

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    #1

    My 2.7i Build

    I ran a stock 2.5L engine w/ metric blues at 10psi for a few months before the headgasket blew. My goal is to make a reliable engine to boost at a reasonable cost.

    I've got a 2.5i engine. 250k on the engine. Head rebuilt in '05 and looks brand new, block is clean and looks in good condition.

    Got an S-ETA bottom end. Sat for a while, so it's dirty and the coolant passages are rusty.

    My plan is to take the 2.7L internals and put them into the 2.5L block. Mild rebuild at the same time.

    Here is the plan for the rebuild:

    Main bearing set - 11211706847 - $88.40
    Connecting rod bearings - 11241280582 - $47.30
    Connecting rod bolts - 11241713342 - $70.80 ($5.90x12)
    Standard 83.98mm Piston ring set - 11251713192 - $127.80
    Bottom end gasket set - 11111730875 - $37.91
    (total $372.21) + timing belt, few misc. gaskets

    Resurface and hone block - $200?

    Resurface head - $100

    ARP headstuds + stock thickness Cometic headgasket - $440

    Critiques or advice?

    '88 325is
    VP UT of Austin Autoholics
    BMWCCA 380364
    Tags: None
    #2
    Get valve reliefs cut in to the seta pistons to prevent piston to valve contact instead of surfacing the block.

    1986 325es (69k) Garage Queen Buy It Now 10k;1986 325es (track rat) 2.7i How-To & 1.1/1.3Motronic UpGrade
    1991 318is (daily driver) 1991 318is M42 Maintenance How-To;1989 325i (parts car)

    Comment

      #3
      Originally posted by kenika65 View Post
      Get valve reliefs cut in to the seta pistons to prevent piston to valve contact instead of surfacing the block.
      Is that really necessary? I was under the impression that s-eta 2.7 internals were "drop in" to the 2.5 block.

      '88 325is
      VP UT of Austin Autoholics
      BMWCCA 380364

      Comment

        #4
        Originally posted by Jordan325iC View Post
        Is that really necessary? I was under the impression that s-eta 2.7 internals were "drop in" to the 2.5 block.
        -They are...
        1989 cirrisblau-metallic 325i

        Comment

          #5
          They are im just saying to do it so that when or if your timing belt breaks you have nothing to worry about! It is good insurance.

          I was saying instead of spending money on surfacing the block.

          1986 325es (69k) Garage Queen Buy It Now 10k;1986 325es (track rat) 2.7i How-To & 1.1/1.3Motronic UpGrade
          1991 318is (daily driver) 1991 318is M42 Maintenance How-To;1989 325i (parts car)

          Comment

            #6
            Originally posted by kenika65 View Post
            They are im just saying to do it so that when or if your timing belt breaks you have nothing to worry about! It is good insurance.

            I was saying instead of spending money on surfacing the block.
            Ah, ok. I think I have to re-surface the block to get it within a certain "smoothness" as required by the MLS gasket.

            BTW, cool to see another local person.

            '88 325is
            VP UT of Austin Autoholics
            BMWCCA 380364

            Comment

              #7
              Update, well I've been talking to some local shops. K&K welding and Precision Engine. I am trying to decide between o-ringing the block or welding the head. I will save some money by not going with an MLS gasket.

              '88 325is
              VP UT of Austin Autoholics
              BMWCCA 380364

              Comment

                #8
                Why would you use a 2.5 block? the 2.7 block is the same although it has much better 360 degree oiling on the mains
                I would take the s eta block to the machine shop and have it hot tanked to see if it can be salvaged....it would have to be pretty far gone rust wise to be scrap!


                2.7L M20 11:1 COMP 195 whp Dyno Dynamics 2380lbs

                Comment

                  #9
                  Originally posted by Dyno4mance View Post
                  Why would you use a 2.5 block? the 2.7 block is the same although it has much better 360 degree oiling on the mains
                  I would take the s eta block to the machine shop and have it hot tanked to see if it can be salvaged....it would have to be pretty far gone rust wise to be scrap!
                  This "budget" build has already spiraled way out of control, so I try to reduce costs wherever I can. I don't think the benefits of the S-ETA block are worth the cost of saving that old block.

                  Plus, this car has gone 260k with the same block and it is still in great condition. Call me sentimental, but I don't want to separate the two.

                  '88 325is
                  VP UT of Austin Autoholics
                  BMWCCA 380364

                  Comment

                    #10
                    My take on the situation form another boostoholic... I would O-ring the block and run a stock HG with ARP studs. If there is anyway to have the head welded, get it done. I regret not o-ringing. I am just running a MLS with a welded head so far, so good. I hope all is well for a long time. Replace the oil pump while you are in there if you can afford it. What EMS are you running? You should really figure out WHY the HG blew not... overbuilding the engine to compensate for a problem somewhere else. My take on the situation was overbuilding the engine AND getting spot on tuning, trying to go for reliability. So far I have 2k hard miles on my motor and its working great.
                    :: PNW Crew ::
                    '87 325 4dr, '74 2002

                    Comment

                      #11
                      Originally posted by Dyno4mance View Post
                      Why would you use a 2.5 block? the 2.7 block is the same although it has much better 360 degree oiling on the mains
                      -Same block!
                      1989 cirrisblau-metallic 325i

                      Comment

                        #12
                        So I have talked to two shops today, both recommended to me from other sources. They both have suggested that MLS gaskets were a better alternative to o-ringing. At this point I am torn. Every e-warrior on this site says that o-ringing and stock gasket is the way to go, whereas every professional shop in my area I talk to says MLS gaskets are better than o-rings. I am very torn, and I have till tomorrow to make my decision.

                        '88 325is
                        VP UT of Austin Autoholics
                        BMWCCA 380364

                        Comment

                          #13
                          At the very least MLS and welded head, the problem is the coolant channels and the tight cylinder spacing, the symptom is blown HGs.
                          :: PNW Crew ::
                          '87 325 4dr, '74 2002

                          Comment

                            #14
                            Unfortunately the "welding the head" boat has already sailed, since the head is already getting milled at the machine shop. The block is at another performance machine shop, but they haven't started work on it yet. $150 to o-ring compared to ~$200 for an MLS gasket. I am seriously losing sleep over this issue.

                            '88 325is
                            VP UT of Austin Autoholics
                            BMWCCA 380364

                            Comment

                              #15
                              O-ring. No question in my mind.
                              :: PNW Crew ::
                              '87 325 4dr, '74 2002

                              Comment

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