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opinion needed piston choice stock rebuilt ....

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  • opinion needed piston choice stock rebuilt ....

    hi guys
    <yes I have searched lol>.
    my M3 has 120mi and I only know head was rebuilt 15y ago and chain guides ,oil pump and chain replaced 5000mi ago . engine runs good but a little low on compression < don't remember numbers >.
    I want to rebuild the engine to start from fresh in case rod and mains need replacement .
    I want to stock rebuilt but a little more power would be ok . will keep stock cams .
    what pistons and compression ratio do you recommend ?use 93 octane most of the time but do use 91 sometimes .

  • #2
    Hi Ertech,
    The answer to your several questions is what your goal is. Perhaps all a 'rebuild' to get the compression up is new piston rings and a valve grind. Or perhaps a complete rebuild with everything new, except the block and head, and then only if the head passes a pressure test. So the choice for pistons is what is available and what is your budget. And the bore wear will help you make that decision. Often the bores will still show the helical honing marks from new, and also many times they are gone. It depends on how the engine was stressed. And the weak link with these engines is rod bearings. In talking with a BMW factory tech at Sears Point several years ago, he remarked that the rod bearings were 'good' for maybe 30 hours of engine time on the track.

    That is two years of on track time and maybe less. For example, with Formula Ford the rebuild is every 10 hours of track time. That's one year of 10 races, 20 minutes of practice, 20 minutes of qualifying and 20 minutes of race.

    And when you go into the engine, you will need new gaskets and lots of labor no matter what you decide. And is good practice to replace everything that can fail between then and the next time you open the engine. And everything also depends on your budget, who is doing the work, what shop you will use for machine work, and how long you plan on keeping the car. Finding a shop that knows what to do and do it properly can be a challenge. For example, the machine shop I use in Santa Rosa recommends replacing the small end rod bushings with new piston pins, and that is good practice. The alternative to a competent shop can be a new block and/or head, or more. And good blocks are now expensive if you can find one. Rebuildable heads and good bearing cranks are getting there as well. The shortage of rebuildable blocks is caused by not replacing the rod bearings soon enough.

    There are two ways to get more power, more compression and different cams. Both have to be changed very carefully. More compression requires fuel with sufficient octane to prevent detonation at full throttle with a warm engine and different cams can intrude on street driving with too much valve overlap for a reasonable idle speed and less torque at low rpm. By low, that is below 4000-4500 rpm depending on the cams chosen. That is most street driving. At least it is easy to change them.

    You can also improve lap times by proper selection of transmission and rear end gear ratios and tire size, but that is not engine related.

    In my experience with pistons for manly street use, I have had good luck with JE forged pistons with 10-1 compression and Sealed Power rings with three piece stainless oil rings. Those rings actually are made for a Mercedes so the set comes with enough rings for six cylinders. They will not knock on 91 (R+M)/2 octane that is the highest one can get on the west coast unless you want to use leaded race gas, and that will kill a cat if you run one. And race gas is expensive, like $8.50 a gallon or more if you can find it.

    Good luck, and if you have questions, ask them.


    • #3
      If I was going to rebuild any of my street engines I would use a forged Evo 2 clone piston. Pick up a little compression bump.
      Ron Checca member on here ( Ron ///Man ) has a Wiseco Evo2 clone piston set he had made up that he has access to.
      Buy a set of those, get them coated install and enjoy the slight compression bump with no downsides in valve clearance, etc (assuming you stay with stock-ish cams).
      Last edited by jimmy p.; 01-12-2022, 07:08 AM.
      jimmy p.
      87 E30 M3 Prodrive British Touring Car
      88 E30 M3 Zinnoberot - Street
      88 E30 M3 Lachsilber - Race (#98 SCCA SPU)
      92 E30 M Technic Cabrio - S14 POWERED!
      98 318Ti M44, Base - Morea Green
      04 Ford F350 - V10


      • #4
        Anyone have more detail on these evo2 clones


        • #5
          Hopefully the bore just needs a hone and new rings, since you are keeping it stock cam shaft I would try and stick with genuine pistons first.
          I went through the pros and cons of aftermarket pistons (along with plenty of procrastination) 10 years ago and made the very expensive decision to install oversize genuine pistons and I am still happy with my choice 10 years later.

          I am 100% behind Larry”s comment do the rod small end bearing regardless if you use old or new pistons, my engine had a lot of wear in the pin and rod small end bearings.
          With refreshing your engine it should have a bit more punch and if you want a bit more, new eprom chip and evo2 cam would work nicely with the original pistons.

          Below is a for sale which may interest you.


          E30 M3 1987
          Mini Clubman GT
          BMW E36 323 Msport
          Toyota Corona
          KTM 200EXC
          Honda CB50 (1979)


          • #6
            Originally posted by Ertech View Post
            Anyone have more detail on these evo2 clones
            I own 3 sets of them, 2 in active engines, 1 spare set in a box. I believe mine are all 1st over, maybe 2nd over its been a while.
            Member Ron Checca (Ron ///Man) had them made up and can get them, they are made for him by Wiseco.
            Ron is a well known S14 engine builder in the Northeast of the US (not sure where you are located).
            They have been in 2 of my engines for at least 10 years, no issues.
            jimmy p.
            87 E30 M3 Prodrive British Touring Car
            88 E30 M3 Zinnoberot - Street
            88 E30 M3 Lachsilber - Race (#98 SCCA SPU)
            92 E30 M Technic Cabrio - S14 POWERED!
            98 318Ti M44, Base - Morea Green
            04 Ford F350 - V10


            • #7
              thanks guys for all the info . don't see the small end bushings for sale anywhere , we should use the BMW motorcycle ones pn 11240618100 ?
              thank you


              • #8
                Originally posted by Ertech View Post
                thanks guys for all the info . don't see the small end bushings for sale anywhere , we should use the BMW motorcycle ones pn 11240618100 ?
                thank you


                Have you asked yourself how are you going to Tune properly your upgraded engine with hi compression and with diff cam timing ? Properly set turn key EMS starts from $4.5k and up..

                I don't think the bike bushing has cut grove in it for oil also they are folded not as the original. Well, even whiteout the grove it will work for what you are using the car for.




                • #9
                  I want to do a stock rebuild with maybe a little higher compression . same cams same timing . will I need to tune differently?
                  if this is not the proper bushing with one should I order?


                  • #10

                    just an idea, do not know if this works. I assume you have the 2.3l version. I just did a rebuild on my 320is with the S14B20. It has the same bore but a shorter stroke. I used the original pistons having a 10.8:1 compression ratio, so a little higher than the S14B23. So if this piston can be used in a S14B23 regarding Valve Clearance etc. this might be an option. They are available also with oversizes. But as I said, not sure if the S14B20 pistons can be used in the S14B23.




                    • #11
                      Hi Ertech,
                      First, the small end connecting rod bushings are not available for M3 rods. The factory doesn't offer them. I have used the same bushing from a 2002 which fits in the rod properly,. except they do not have the circumferential groove on the ID that the stock M3 bushings have. For street use not having the groove works well, while for track use you either have to groove the ID of the bushing, cut it into two pieces to essentially make a groove, or add the second oil hole in the lower part of the rod to let more oil in towards the bottom of the bushing the way it is done for the 2002.. A competent machine shop can do any of these, your call. And since the shop will have to hone the ID of these bushings to match the OD of the new piston pins you are there anyway. The part number is: 11 24 1 338 456, and if you send me your name and address I will send four of them to you for free.

                      I would caution you that until you have had a look at the bores of the block you are rebuilding, buying pistons now is not a prudent use of your budget. Keep in mind that the most expensive parts are those you buy and do not use. And you should decide what you plan to use the engine for. Forged pistons are stronger than cast pistons especially with a warm or hot engine. The reason cast pistons are more popular for some uses is that they don't expand as much as they warm up so don't cause piston 'slap' when the engine is cold, a noise that the factory thinks the owners of their cars might not consider 'proper'. Once the engine warms up the slapping is gone so it no longer matters. I have run these engines with slapping pistons when the engine is cold with no effect. And you will have to find a shop that understands the difference since the clearance for forged pistons is different than for cast. And one is wrong for the other, both ways.

                      As you must be aware, there is a lot of experience that helps when engines are rebuilt and there is only two ways to get it, one, find out the hard way and two, ask around. As I am not in this for the money I enjoy answering questions, especially if it helps. And understanding what you are attempting to do is always good for all.
                      Larry. My contact is: [email protected].


                      • #12
                        Spun a bearing on my s14 in September last year.
                        finally opened it up after Xmas to find the cause was most likely oil starvation = failed oil pump. Damage is minimal.
                        So one thing has led to another and now I'm planning a 2.5 Stroker Kit with the bells and whistles.
                        it's originally a 2.3 late model 215hp engine with 156k miles. Previously rebuilt in 2014 by a workshop I won't name. Poor workmanship is all I can say.
                        Car has had a nut and bolt restoration using every new part where possible. Recycling only parts that are NLA. Uprating everything possible along the way

                        Ultimately it's a street car I intend cherish forever and hand down one day to a loved one. So budget has not played a part in this parts list. Moreover reliability/sound/preventative measure/ usable power has taken priority.
                        So far here is my parts list.

                        Schrick Cams 284 276
                        Oem 2.5L Evo3 Crankshaft
                        94.5mm JE Pistons
                        Arrow connecting Rods
                        Compression Ratio 11.5.1
                        Heavy Duty pins - Yes
                        Dome Coating - Yes
                        Skirt Coating - Yes

                        VAC Coated rod Bearings
                        VAC Coated main Bearings
                        VAC Oil pump upgrade/fix kit
                        VAC S14 Megasump with Baffle
                        Paper oil pan gaskets (upper/lower)
                        VAC crank Trigger 60-2
                        VAC+ Multi Layer Steel Headgasket (thickness to be established)
                        VAC Heavy Duty Alternator Bushings
                        VAC Throttle position kit

                        E30 M3 S14 wideband o2 sensor
                        S14 fast reacting intake sensor
                        Fuel pressure sensor
                        Fuel temp sensor
                        Oil pressure sensor
                        Oil temp sensor
                        EGT sensor 8mm or 7mm
                        ECU - LINK OR SYVECS
                        Carbon airbox DTM - Markus
                        Weicher 39.5" fake carbon strut brace
                        Fuel rail adapter for fuel pressure regulator AN6

                        CSF Oil cooler kit + sandwich plate/ black hoses

                        Vibra technics engine mount

                        oem bmw s14 oil pump
                        Oem bmw groupN transmission mount # 23711417246KT
                        OEM crank damper
                        Schrick Valves
                        Schrick Springs
                        E36 M3 oem Cam Followers
                        New ignition wiring oem
                        All round ARP bolts Main/head/flywheel

                        I have sent my getrag 265 gearbox and 3.25 diff to Neil at Allgears in Worksop for a full rebuild using all new upgraded internals.

                        I did opt for the Turner motorsport shifter rebuild kit with polyurethane bush to fit over the rebuilt gearbox

                        Alongside this exhaustive parts list I am planning to send the cam covers for refinishing.

                        I have a full extended alcantara interior on order with Amxperformance since last year. This includes
                        alcantara trim dash
                        Footwell Speaker covers
                        recaro sr3 heated seats
                        door cards front and rear
                        mtech2 370mm steering wheel alcantara

                        I am in the process or procuring air conditioning parts for retrofit using a more modern system but implementing the oem heater matrix. (This part has me stuck. Will update as It progresses)

                        This has consumed me to say the very least.

                        I am not an engineer and have a very basic understanding of s14. I have the help of good friends and this forum.
                        I'm sure I've missed a load of things