Announcement

Collapse
No announcement yet.

2.7i Build Thread, Guide, and Learning Experiences

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    2.7i Build Thread, Guide, and Learning Experiences

    Hey guys, I'm in the process of building up a 2.7 stroker and thought I would document the process for those wanting to learn how to do it as well as a cost breakdown and my learnings throughout my build. I sometimes found it a little difficult to find all the information I needed, so hopefully this can be a simplified resource for those looking to build up a 2.7i

    A little bit of background on the events that led me to building a 2.7i. I bought a clean title '84 eta with a bad motor that had sat for nine years prior to buying it my senior year of high school for $250. Shortly after I bought a salvaged '89 325is that had been in a rear end collision for $950, So I did what any dumb 18 year old would do and swapped almost everything from the is into the eta shell. The only parts original to the car are the tail lights, the heater core, and the doors. I spent the next year and a half working on the car on my breaks from college, and after all that time I finally got it to run. That lasted for a week before the clutch fan went bad and the small nipple on the thermostat housing broke off. Causing me to piss coolant all over the SMOG line and overheat the motor... I had a choice to either throw new rod bearings in, swap in a new motor, or push my 2.7i build up a couple years, and I decided to send it on a stroker. With that out of the way, let's dive right in.

    DISCLAIMER: This is my first time ever building an engine or even taking one apart for that matter. I am a 20 year old with his first project car, so I am learning and posting my findings here. This is meant to be a helping hand to those who are looking to build a 2.7i for the first time and to show that is a very attainable build, even to a novice.

    ------------------------------------------------------------------------------------------------------------

    I plan on building the car up in stages. The end goal is to have around 200+whp n/a for a fun canyon carver/daily.

    Stage 1: Barebones 2.7i with new gaskets
    Stage 2: Rebuild head, deck it all the way down, adjustable cam gear, hotter cam
    Stage 3: Megasquirt standalone. I want to learn how to tune, and this seems to be the best route for that
    Stage 4: ITB's. Pretty self-explanatory.

    Some ideas I'm currently contemplating: Seta crank, seta rods, b25 pistons with decked down block. Currently going full Seta on internals but I may switch it out later on to get better compression. Either that or custom pistons.

    This initial post will go over stage one. I will be adding to this thread with each stage.

    ------------------------------------------------------------------------------------------------------------

    Helpful Resources:

    2.7i breakdown on R3v
    https://www.r3vlimited.com/board/for...de-2-7i-how-to

    DBO Seta stroker parts 1 and 2
    https://www.youtube.com/watch?v=NArjK3hegVQ&t=8s
    https://www.youtube.com/watch?v=vnjm1kGQ7Wg&t=273s

    M20 rebuild guide:
    https://nasaspeed.news/tech/engine/bottoms-up-rebuilding-a-bmw-m20-short-block-for-your-spec-e30/

    ------------------------------------------------------------------------------------------------------------

    Budgeting Based on an M20b25 Base:

    Seta crank, rods, and pistons: $320 shipped courtesy of R3v member E30335i

    Elring seal/gasket kits, rod bearings, main bearings, rod bolts, piston rings, and head bolts: $400

    Machine shop work (head decked, tested, and cleaned. Block decked and cleaned): $250

    Total: $970

    NOTE: The gasket rebuild kits are optional, but most everything else is mandatory. If you want to save $100, then don't get them. But why wouldn't you spend the little bit extra to have that added layer of reliability? The hope is to never do this again, so now's the best time to replace all those seals and gaskets.

    ------------------------------------------------------------------------------------------------------------

    As it stands today, I am waiting on my head and block to return from the machine shop, but I have some valuable learnings that I think a lot of novice wrenchers would benefit from. These are in no particular order, just writing what comes to mind.

    1. It is not nearly as scary as you would think. If you have a seta motor already, the job is even easier than what I'm having to do. Once you get the engine out of the car and onto the stand, it comes apart a lot quicker and easier than you'd expect. It's been a really interesting experience seeing how the insides of an engine look and the M20 is a great choice for the first time engine builder. It's a very simple motor and it isn't hard to see what goes where.

    2. A removable core support will make your life a lot easier for removal and installation. This is the third time I have pulled an M20 out of an E30, and the removable core support makes a world of difference. Instead of having to drop the whole front end down to just barely get the engine over and out, or unbolting the trans from under the car, you just free the engine of anything attaching it to the rest of the chassis and pull it straight out.

    3. Machine shops suck. I tried to find a cost-friendly shop and I'm paying the price for it. They told me it would be done this past Tuesday, but I give them a ring on Thursday and they tell me they haven't even started it yet. I've talked to my buddies about the subject, and it seems this is pretty common for small manufacturing shops. Be prepared to wait a lot longer than you expected to get your stuff back.

    4. It's going to take you a lot longer than you thought it would. Delays happen, life gets in the way, and everything you do for the first time is going to take twice as long as you expected it to. Do yourself a favor and get everything you can get ahead of time, that way you spend as little time as possible waiting for parts to show up. Don't pull the motor out of your daily and say "I'll have this done in a week." It will almost definitely take more than a week, but that's okay. Patience is a virtue.

    5. Get an impact gun and a u-joint for taking stuff off. Some people are against using impacts on engine bits, but as long as you're careful and always have it on loosen, you will speed things up significantly. Impact is only used for taking things off!!!

    6. Loosen the crank bolt with the power of the starter. It's torqued to 300-something nm, and while you can get it loosened on an engine stand, it is a royal pain to do so. Do yourself a favor and break the bolt free while it's in the car. There are plenty of writeups on how to do it "safely."

    7. Pull out the electrics with the motor unless you absolutely can't. There are a lot of small connectors that are a pain to get to in the car, so why not make your life easier and take it off when you have more space to do so?

    8. You are going to dump a ton of fluid on the ground, primarily coolant. You're going to spill a little when you undo the bottom hose on the radiator, and then you're going to spill a lot when you start undoing other things like the water pump or the heater core hoses. Just seems to be that way so be prepared to clean up a mess.

    9. Spend the extra time to clean everything you can while you have more space. This is a rare opportunity you will get to clean the little nooks and crannies you would probably never even see with the motor in the car. You will thank yourself later when you go to work on the car and you have a relatively clean engine bay.

    10. Research, research, research! If you don't know the answer to a problem you're having, chances are someone else had that some problem. There's so much useful information here on the forum and on youtube. All it takes is a few minutes in google and you can usually find what you're looking for.

    ------------------------------------------------------------------------------------------------------------

    There are a lot of people on here who would discredit the 2.7i and call it a waste of money, saying you'd be better off to swap in an M50/M52. While those motors do produce more power, I fell in love with E30's for their mechanical simplicity and I feel that swapping in a newer engine takes away from that. There's also something to be said for messing up the weight distribution of the car, but it's probably not by a whole lot. None of this is to say that doing a swap is the wrong way to go, an M20 stroker just fit my needs/goals best. To sum up my feelings on the matter, I think the 2.7i is a budget friendly option that anyone can do to get more out of their E30 than its stock form.

    With that, I am going to wrap up this initial post. As I continue to progress through my build. I'll try to keep this thread updated and add any more lessons I learn. Please keep in mind that I am a broke, 20 year old college student, so updates may be few and far between. If anyone has something they would like to add, feel free to tag in and share your experience.
    Last edited by Lefty_lifestyle44; 12-08-2020, 03:55 PM.

    #2
    IMO should use M20B25 piston with 885 head, just deck the head nominally 2mm and adjustable cam gear almost a point of CR over the SETA if you get the piston and head nice and close. Also with deeper valve reliefs quite a bit better suited if cammed. Should already have the slugs from old motor?
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

    Comment


      #3
      Subscribed! I plan on doing a stroker too once my head comes in.
      sigpic84 325e

      Comment


        #4
        Originally posted by digger View Post
        IMO should use M20B25 piston with 885 head, just deck the head nominally 2mm and adjustable cam gear almost a point of CR over the SETA if you get the piston and head nice and close. Also with deeper valve reliefs quite a bit better suited if cammed. Should already have the slugs from old motor?
        It's my understanding that you can't use the 2.5 pistons on the 2.7 crank because they don't have the reliefs cut at the bottom of the piston. If you watch DBO's part two video he shows a 2.5 piston he tried to use that broke after 2 hand-cranked revolutions. Still using the 885 head

        Comment


          #5
          Originally posted by Lefty_lifestyle44 View Post

          It's my understanding that you can't use the 2.5 pistons on the 2.7 crank because they don't have the reliefs cut at the bottom of the piston. If you watch DBO's part two video he shows a 2.5 piston he tried to use that broke after 2 hand-cranked revolutions. Still using the 885 head
          Digger/ForcedFirebird will chime in, but the m20b25 uses a 75mm crank and 135mm connecting rods (172.5mm at TDC = 135mm +75/2mm). The eta/seta uses an 81mm crank and 130mm rods (170.5mm at TDC = 130mm + 80/2mm). To make it work with the b25 pistons (which have a better/tighter match to the 885 head) with the 81mm crank, you need to use the 130mm rods. This will result in the 81mm crank, 130mm rods, and b25 pistons roughly 2mm below their nominal position at TDC, which will lower your compression ratio. This is why either the block or head will need to be decked ~2mm to restore compression. Restoring compression will cause your timing to be off, so an adjustable cam is a good idea.

          Read through FF's dyno thread for more info:
          https://www.r3vlimited.com/board/for...20-dyno-thread
          sigpic
          1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
          1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
          1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

          Comment


            #6
            Originally posted by McGyver View Post

            Digger/ForcedFirebird will chime in, but the m20b25 uses a 75mm crank and 135mm connecting rods (172.5mm at TDC = 135mm +75/2mm). The eta/seta uses an 81mm crank and 130mm rods (170.5mm at TDC = 130mm + 80/2mm). To make it work with the b25 pistons (which have a better/tighter match to the 885 head) with the 81mm crank, you need to use the 130mm rods. This will result in the 81mm crank, 130mm rods, and b25 pistons roughly 2mm below their nominal position at TDC, which will lower your compression ratio. This is why either the block or head will need to be decked ~2mm to restore compression. Restoring compression will cause your timing to be off, so an adjustable cam is a good idea.

            Read through FF's dyno thread for more info:
            https://www.r3vlimited.com/board/for...20-dyno-thread
            Would love to get confirmation on this. My 2.5 pistons are in good shape so I may swap them out when I go stage 2. Unfortunately I'm a little too far along in stage one now to make the change but if it works and makes better power I would definitely consider going this route.

            Comment


              #7
              Originally posted by Lefty_lifestyle44 View Post

              It's my understanding that you can't use the 2.5 pistons on the 2.7 crank because they don't have the reliefs cut at the bottom of the piston. If you watch DBO's part two video he shows a 2.5 piston he tried to use that broke after 2 hand-cranked revolutions. Still using the 885 head
              It depends on the specific piston there are 2 manufacturers and each has a few different skirt shapes so in total atleast 4 or 5 skirts. I’m sure some have really long skirts but you can simply machine a bit away if you’re unlucky enough to have the large skirt variants. It’s easy to check with parts in front of you and you don’t need to assemble into a block and break things if you think a little unlike some people who make YouTube content
              89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

              new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

              Comment


                #8
                Forced Firebird has a thread on M20 pistons IIRC, it'd be a good resource for you OP.

                Comment


                  #9
                  Originally posted by roguetoaster View Post
                  Forced Firebird has a thread on M20 pistons IIRC, it'd be a good resource for you OP.
                  Thanks for the lead, I’ll take a look into it

                  Comment


                    #10
                    Update: Just got a call from the machine shop and was told that my cam had developed grooves on it and it's eating away at itself. Looking into new cam options and probably going with a stock Febi replacement for now instead of going with something more aggressive. I'll be adding "rebuild head" to stage 2.

                    Comment


                      #11
                      Originally posted by Lefty_lifestyle44 View Post
                      Update: Just got a call from the machine shop and was told that my cam had developed grooves on it and it's eating away at itself. Looking into new cam options and probably going with a stock Febi replacement for now instead of going with something more aggressive. I'll be adding "rebuild head" to stage 2.
                      It seems pretty expensive to build 1.5 engines when you only need 1 good one.
                      sigpic
                      1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
                      1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
                      1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

                      Comment


                        #12
                        Originally posted by McGyver View Post

                        It seems pretty expensive to build 1.5 engines when you only need 1 good one.
                        Yeah, this project is becoming a bit of a bear, but I’ve wanted a 2.7i since I first got the car so bombs away it is. I don’t plan on going stage two with the build for another year or so due to funds, so this seems to be the best route for me. I could buy a used head but there’s always the possibility of getting a POC and being even worse off. This is hopefully my forever car so I don’t mind spending a little extra to do it right.

                        Comment


                          #13
                          A regrind is about $225 cant be much more than new FEBI as a "temporary" thing
                          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                          Comment


                            #14
                            Originally posted by digger View Post
                            A regrind is about $225 cant be much more than new FEBI as a "temporary" thing
                            I got the febi cam for $160 shipped via autohausaz. May not seem like much but I have to save wherever I can. I haven't gotten to see the old cam, but the machine shop told me it needed to be replaced. If I had the money right now I'd just send it and completely rebuild the head with a more aggressive cam, but that isn't the situation I am in.

                            Comment


                              #15
                              I get that you're trying to save money where possible, but if you're going to rebuild the head for a new stock pattern Febi cam, you might as well spend the extra $60 to rebuild it with a cam that's better matched to the bottom end and your performance goals. If you're putting in a new cam, you're going to need to either replace or resurface your rockers. So you might as well change the valve stem seals and lap the valves, which may require replacing valve guides if they're out of spec. Doing it correctly is more than just replacing the cam. It's more expensive now, but the engine will be done and you won't have a second rebuild in the future.

                              If that's just too much cash for right now, why not replace the cam with a used cam and hope for the best?
                              sigpic
                              1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
                              1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
                              1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

                              Comment

                              Working...
                              X