Announcement

Collapse
No announcement yet.

2.5 Pistons with 2.3 crank

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

  • 2.5 Pistons with 2.3 crank

    Hey fellow s14'ers. I am new to the forum (from Australia) and want to complement on the posts. This has got to be one of the best unique car resources around. I wish I knew about it when I first got into e30 M3's! First drove one in the US in 1987 and fell in love. Got my first one in Aus in the mid 90's and have had quite a few since. All imported and converted to right hand drive (shame though it is to have to spread the headers).

    Currently have one for track days (link to pic below):
    http://www.bmwclubnsw.asn.au/gallery...5-22%20052.JPG

    Question for you guys is, has anyone ever made the error (stupid) of installing a 2.3 crank on a set of the 2.5 wiseco pistons designed for use with the 2.5 crank and 2.3 rods? I got caught out by the stock part numbers listed under the E3 chassis number and the stroke difference is pretty slight, so it wasn't obvious with the eye.

    Anyway, I am now running a full 2.5 (48mm throttles, big valves, 292/284 cams, etc) with a 2.3 crank! Compression must be down a fair bit and I am trying to work out whether it is worth me pulling the engine again to install the 2.5 crank?

    Any thoughts?

    Shot of my cabriolet below too
    http://www.bmwclubnsw.asn.au/gallery...-shine-064.jpg
    1990 Sport Evo M3 Brilliant Red
    1986 M3 (Nero Rabbit) Diamond Schwartz
    1990 R32 GT-R Wine (1000whp)
    2008 997.1 Turbo Porsche (750hp)
    1999 Evolution VIRS

  • #2
    you just made the engine more "oversquare"(i think thats it)...you have a shorter throw...so you lost some of the leverage what would've gotten you some more torque...your engine will just be a little moer peaky.

    it'll still work...you just have a 2.4 or there abouts
    Last edited by ADA///M; 10-13-2005, 04:22 AM.

    Comment


    • #3
      Have a chat with 'ShepsEVO3' on this forum, he just found out that his sport evo had its engine rebuilt with a 2.3 crank before he bought it...!!!!

      link to the chat on BMW UK

      http://www.bmwcarclubforum.co.uk/for...TID=22070&PN=2
      Last edited by UK215M3; 10-13-2005, 05:24 AM.

      Comment


      • #4
        Originally posted by UK215M3
        Have a chat with 'ShepsEVO3' on this forum, he just found out that his sport evo had its engine rebuilt with a 2.3 crank before he bought it...!!!!

        link to the chat on BMW UK

        http://www.bmwcarclubforum.co.uk/for...TID=22070&PN=2
        THAT BLOWS :sosad:

        Comment


        • #5
          Originally posted by UK215M3
          Have a chat with 'ShepsEVO3' on this forum, he just found out that his sport evo had its engine rebuilt with a 2.3 crank before he bought it...!!!!

          link to the chat on BMW UK

          http://www.bmwcarclubforum.co.uk/for...TID=22070&PN=2
          That's horrible! I'd be pissed to not have gotten what I paid for. The difference between the 2.3 and 2.5 crank is easy to see: the 2.3 uses a 36 mm nut on the belt pulley, where the 2.5 uses a 30 mm bolt. Never buy a "2.5L engine" without verifying this first!

          In general, the 2.5 crank is of superior design. Despite it's longer stroke the 2.5 is approximately 6 lbs lighter than the 2.3 crank and it has a better swept design for improved windage.

          As to the original question, if the engine runs well I'd be inclined to leave it alone - but I'd personally cry myself to sleep at night, thinking of how it should have been. :sosad: The next step might be to swap the head gasket to the Grp A version, which will regain some of the lost compression. But even that would be a lot of work and the gasket is expensive. (North of $300 USD) Or try a thin metal VAC 2.5 gasket, which is cheaper and maybe even better (but still a lot of work).

          -Dietrich

          Comment


          • #6
            Originally posted by Zeus
            (shame though it is to have to spread the headers).
            Ron I had my extractors (headers) custom made up here in Brisbane. Looked at the cut and shut option but felt I would have a custom set made. Stainless steel ceramic coated. $650AUD if memory serves me correct.

            Originally posted by Zeus
            ........and I am trying to work out whether it is worth me pulling the engine again to install the 2.5 crank?

            Any thoughts?
            Personally I would have engine pulled down and redone. You have everything else going on and I would want it done properly. Thats just my opinion, if your happy with it the so be it.

            Who rebuilt the engine? Was done in NSW or Qld? They would be paying for their stuff up if it was their parts ordering mistake.

            Cheers
            Dave
            Last edited by OZM3; 10-13-2005, 11:26 AM.

            Comment


            • #7
              I think the Group A gasket is like 0.5 mm thinner and raises the comp ratio half a point. It would follow from the 84 vs 87 mm stroke-length that you have effectively lowered the comp ratio to somewhere in the 8.5:1 ballpark.

              I would pull it, otherwise it'd be wasted effort and money, and you got some sweet components in there!

              Anders
              Last edited by Anders; 10-13-2005, 11:49 AM.
              Anders

              "Objects in mirror are losing..."

              Comment


              • #8
                I think pull it is the answer. Particularly if we are only around 8.5:1!!!! The pistons probably don't even come up to deck height, so that is probably right. I think they are supposed to pop 20 thou" when done with the 2.5 crank and they must be a mm under. Still pounded down 210 at the wheels, but all up top and we should be up around the 225 mark with a bit more under the curve if we can get the compression back.

                Problem is the cab has just had a respray and I hate to think of getting the engine out again without marking the paint. A real dissapointment, but has to be done. We got the crank and supplied it to our guy in NSW, so probably our fault.

                Dave, you obviously know my old man. The race car is mine, and we went halves in the 2.5 rebuild on the cab (to soften the pain). We have a guy that does extractors down here now, but $650 sounds really cheap.

                Poor guy with the Sport Evo. I know how he feels!

                Adam

                Adam
                1990 Sport Evo M3 Brilliant Red
                1986 M3 (Nero Rabbit) Diamond Schwartz
                1990 R32 GT-R Wine (1000whp)
                2008 997.1 Turbo Porsche (750hp)
                1999 Evolution VIRS

                Comment


                • #9
                  Originally posted by Zeus
                  We got the crank and supplied it to our guy in NSW, so probably our fault.
                  I wouldn't say it was your fault, you're builder should have caught that. I'd have real problems with a builder who didn't verify clearances etc as he built his motors. Maybe it's ok to throw together some half assed 'Merican Chevy 350, but the S14 requires a little more attention to detail.

                  No disrespect to you builder, but it doesn't seem like his work was very thorough.

                  Respectfully,
                  Jake

                  Comment


                  • #10
                    Old thread dug up, but I was searching for something else and came across this...

                    An Update to my engine. It had infact been rebuilt by a previousl owner, not the one I bought it from, or the one before that, but the one before that! If you get my drift. It had been into the parts supplying dealer for a power loss problem after the engine was rebuilt (not very well so it would seem) and there is an invoice to confirm the crank was wrong. I missed this when looking through the invoices. My fault - no-one elses. Now, when I test drove the car, it felt flat, but it rev'd well amd when going past 4000 rpm it felt like it had some grunt-ish lol.

                    Anyway, yep the crank was a 2.3. But thankfully everything else has proved to be 100% sport evo.

                    I have pulled the engine apart, renewed all the valve guides, exhaust valves, pistons, oil pump, crank (ofcourse) and am going to move the inlet cam to the exhaust side and fit a Scrick 284 on the inlet. The whole engine has been blueprinted, matched and ballanced. I have resisted doing any porting to the head, but the valve guides do not protrude into the ports like the standard one do. So I have just optimised what I have there and I had the head flow checked and the operator came back with a spec of cam which would do the job which matched the spec of the Schrick 284.

                    I am looking forward to getting the engine back, in the car, run in and mapped on my dyno. I am just wondering whether to fit the Rongineer airbox and fit TPS to remap against throttle position to make full use of the cam changes and whats been done to the engine. From other conversions I have done, it is very worth while and I feel it would be rude not to.

                    Will keep intouch with the results and progress.

                    Paul.
                    E30 M3 Sport Evolution Black
                    E30 M3 Sport Evolution Red
                    E30 M3 Evo II Red
                    E30 M3 Evo II Blue
                    E30 M3 195hp Black
                    E30 318 is White
                    E30 318 is Red

                    Comment

                    Working...
                    X