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Thread: S52 eagle rods w/stock pistons

  1. #1
    Join Date
    Jun 2019
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    Glendale Az
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    1998 e36 M3/4/5

    S52 eagle rods w/stock pistons

    I’ve tried to look for people doing this just upgrading their rods i.e. eagle rods, and keeping their stock pistons but I’ve never seen/heard of anyone doing this I know all M5x-S5x can handle 500hp/tq till the rods bend I just want to see if anyone had done this . Thanks 👍

  2. #2
    Join Date
    Jun 2005
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    New England
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    F90 M5; E36 M3 Turbo
    With a 2.5 to 2.8L and enough boost to bend the stock rods, wouldn’t you be concerned about breaking ringlands on stock pistons? At least run a bigger gap on the rings.

    I made 600 rwhp with an S52 with aftermarket pistons and stock rods, with torque hitting something like 560 lbs. I never tried stock pistons and aftermarket rods. I am now fully built.

    Hope you will be running E85 to add octane and run cooler to reduce the likelihood of detonation if you try this. Might find more info in the FI subforum. People have tried just about everything. How long does the motor need to last?

  3. #3
    Join Date
    Apr 2015
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    Tennessee
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    1998 BMW 328i
    The reason you dont hear of this is because most people that go thru the trouble of stripping down the block and putting in new rods arent going to ignore the pistons.

    Either all or nothing I say

    Sent from my VS987 using Tapatalk

  4. #4
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    F90 M5; E36 M3 Turbo
    Rods are $500 and easy to swap. Pistons are twice that and a lot more work to fit. I see the logic, but would probably just leave the stock rods and pistons until ready to spend the money to build a motor and replace both.

    When I started, these motors were a lot younger. Now they are all 20-27 years old. Many are probably near the point where they need a rebuild. Doubling or tripling the power will make that point happen sooner.

  5. #5
    Join Date
    Jun 2019
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    1998 e36 M3/4/5
    I want it to last for a long time tbh I plan on supercharging it there’s a kit where you can bolt up a M122H supercharger from a GT500

    - - - Updated - - -

    Quote Originally Posted by pbonsalb View Post
    With a 2.5 to 2.8L and enough boost to bend the stock rods, wouldn’t you be concerned about breaking ringlands on stock pistons? At least run a bigger gap on the rings.

    I made 600 rwhp with an S52 with aftermarket pistons and stock rods, with torque hitting something like 560 lbs. I never tried stock pistons and aftermarket rods. I am now fully built.

    Hope you will be running E85 to add octane and run cooler to reduce the likelihood of detonation if you try this. Might find more info in the FI subforum. People have tried just about everything. How long does the motor need to last?
    I want it to last for a long time tbh I plan on supercharging it there’s a kit where you can bolt up a M122H supercharger from a GT500

  6. #6
    Join Date
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    F90 M5; E36 M3 Turbo
    I have been following that positive displacement supercharger kit and think this latest version has potential. Hopefully someone will dyno a sorted out and tuned example so we can see what it actually does. There is one guy fiddling around with a stand-alone ECU but I would not recommend that. There is another guy who does not have his kit yet but is practicing tuning his stock ECU, which I think is the better approach since with larger injectors and a higher flowing HFM it can support 800+ rwhp (whether obd1 or obd2 ECU).

    For around 500 lb rwtq, a stock rebuild with a compression lowering head gasket kit works fine. If you want more, I would use aftermarket rods and lower compression aftermarket forged pistons with ringlands designed for the stress of boost. If you ran only E85 fuel or had a stand-alone ECU with an ethanol content monitor and failsafe to pump gas boost levels, you could use stock compression.

    If you just leave your engine alone except for a lower compression head gasket kit, it should do 500 lbs rwtq. Many have done this over the years and many still do this. It’s the low buck approach. But these engines are all 20-25 years old now so you have to accept greater risk of failure than when doing this on a younger motor.

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