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  1. #1
    88-jac's Avatar
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    Cool GPRXP Turbo rebuild - what pistons?

    I've pulled the motor for a rebuild in my GPRXP.

    It's running a GTX2871r.

    Never really turned the boost up too much, but going to a tad more once I've rebuilt the engine.

    What pistons should I go with? Thinking CP .25 over to clean the bores up?

    Am I best sticking with 9:5:1 or changing to 8:4:1?



  2. #2
    88-jac's Avatar
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    Engines just come back from Soda Blasting

  3. #3
    Bob 1tommygunner1927's Avatar
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    IMO, I would use 8.4:1 CP pistons. After having the the block decked (to ensure flatness), and the head milled for the same reason, compression will be higher, nearly 9:1. Secondly, now would be a good time to check into various engine coatings: pistons, bearings, oil pumps, valves/springs, etc.
    Its not about speed, but longevity!

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  5. #4
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by 1tommygunner1927 View Post
    IMO, I would use 8.4:1 CP pistons. After having the the block decked (to ensure flatness), and the head milled for the same reason, compression will be higher, nearly 9:1. Secondly, now would be a good time to check into various engine coatings: pistons, bearings, oil pumps, valves/springs, etc.
    Its not about speed, but longevity!

    I agree! Here are the pistons you want. Set clearances at .0045
    https://www.4-tecperformance.com/ind...oducts_id=4434

  6. #5
    88-jac's Avatar
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    I was thinking 8:4:1 myself

    I've noticed this guy / supplier:
    http://jsdmachineworks.com/cp-piston...tons-set-of-3/

    He seems to offer the CP pistons with the coatings done.

    Would you add the 'gas ports' and the 'DLC pins' too?

    Who sells coated bearings for a 4tec? I've not seen anybody selling them.

    Heads already built - Ferrea valves / Supertech springs.

    It's already got ARP cam bolts, head studs/nuts and flywheel bolts. I'm going to order ARP main studs too.

    I'm in the UK, so getting parts / decent 4tec work done is a little more tricky for me.

  7. #6
    Bob 1tommygunner1927's Avatar
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    Gas ports are not needed for your build....put that money towards the piston coatings.

    I used PolyDyn in Houston, Texas for piston coatings.

    https://www.polydyn.com/pistons

  8. #7
    88-jac's Avatar
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  9. #8
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  10. #9
    88-jac's Avatar
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    Not mine, but think I'm going to do the same / use the same guy


  11. #10
    no being a smart ass but why a lower cr . Are you only running 91 oct or what fuel , I'm lost what is your intent with ski racing it just a toy to go play with the guys .how much boost there is a lot of variables . different cam can play a big roll too . so more information would help as for piston coating if it has it fine if it doesn't fine too . i like je piston's or ross pistons cp is good . just run a good oil . .

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