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best pistons for mini me?

Discussion in 'Engine Building' started by CRX2NR18, Mar 31, 2004.

  1. CRX2NR18

    CRX2NR18 Senior Member

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    i am puttin an A6 block and Z6 head in my crx, i already got everything. to bad my head gasket went out this week on my HF so i gotta fix that , but its almost all back together. Anyways which pistons should i use for mini me? Z6? A6? or HF? i heard HF will give you higher compression? hf pistons on a6 rods..w ill that be good?
    this is a N/a mini me too, no turbo will be on this
     
  2. hybrid4

    hybrid4 Senior Member

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    Ive heard the same thing about the hf pistons. I just finnished my minime a6-y8, and my compression is 160 psi. Id say, dont change your pistons, but thats just my opinion. I think if you use a y8 head gasket, it will bump it up a little.
     
  3. reckedracing

    reckedracing TTIWWOP VIP

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    there's a huge diffrence between compression of the cylinders and compression ratio.... apples and oranges dear sir
     
  4. Projectzc

    Projectzc Senior Member

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    Ok You can not use HF pistons. The hf engine is a 8 valve engine all the other heads are 16 valves. Meaning the hf pistons do not have reliefs for the extra 8 valves. You will bend them. http://www.knology.net/~jediklc/D.htm

    Try this site it is a compession cauculator

    What ever you choose make sure you use new rings oilseals and have the cyl. honed at least if not bored. After 150,000 miles they tend to egg shape you will blow oil at high rpm.
     
  5. BseriesKllR

    BseriesKllR Senior Member

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    Ok well if your building a Race engine with big cam then you should try the ZC psitons that will bring you to 12.4:1...but if its just a street setup go with the a6 pistons that will give you 10.2:1 with 2 layer gasket. Good luck with the build.
     
  6. hybrid4

    hybrid4 Senior Member

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    Do explain.
    :hmm:
     
  7. hybrid4

    hybrid4 Senior Member

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    I knew that. someone just told me that the other day. <_< I think he means CX pistons. I heard they put good pistins in there to make up for the shitty heads.
     
  8. Projectzc

    Projectzc Senior Member

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    if you want the CR above 10:1 which you will get with the A6 pistons. Use 88-89 teg pistons also know as ZC pistons. They are dome extra .5 or so.

    CR and PSi in a cyl are different measuements a higher CR will cause a higher PSI They are related but not the same thing
     
  9. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Or just use the stock PM3 pistons that are already in the block with a standard Z6 head gasket to get 10.1:1 compression under a Z6 head, 10.52:1 under a Y8 head-or you can also sub in the 2 layer head gasket if you can get it and have 10.42:1 compression under the Z6 or 10.86:1 under the Y8. If you want to stay under 11.0:1, there's no reason to swap pistons on your mini-me.
     
  10. CRX2NR18

    CRX2NR18 Senior Member

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    okay well what about this, what if i turbo it then, what would be the best pistons to use? cuz i cant decide wether to turbo it or not, i would only run about 9lbs max on race day but run about 6-7 daily. Isnt that to much for 10.1:1 compression?
     
  11. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    If you're going to boost on a mini-me, I would worry more about your stock rods than anything else. The D15 rods are somewhat weak. 9psi isn't too much on 10.1:1 compression- you just have to tune it correctly. Tons of GSRs and B16As boost that much on stock internals- they're all above 10:1. If you want to lower your compression though, you could use some of the dished pistons, like the ones from the D16Z6 or the D16Y8. Those will lower your compression even more.
     
  12. CRX2NR18

    CRX2NR18 Senior Member

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    k thanks but im using D16 rods and block :)
     
  13. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Duh... go back to first post for me. I guess I've been calculating compression ratios all wrong the whole time then. Ignore the numbers I posted up in the other post- those were for the D15 bottom end, and don't think about using the stock D15 pistons- they'll just smash into the head.

    You can do this with your A6/Z6 head combo:

    Z6 pistons, standard Z6 gasket = 9.13:1 (basically a Z6 engine)
    Y8 pistons, standard Z6 gasket = 9.29:1
    A6 pistons, standard Z6 gasket = 9.96:1

    All are easy to boost- just tune your engine properly and you'll be fine. I would just stick with the A6 pistons and throw some mild boost on that, especially if the block is still in good shape. It's a lot easier, and you save a ton of money by not tearing apart the bottom end.
     
  14. CRX2NR18

    CRX2NR18 Senior Member

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    yeah but to bad my block is already apart lol... im puttin in new main and rod bearings, along with piston rings.. so im just goin to use the a6 pistons , and z6 head, so which would be the best head gasket for boost? i heard a full metal 96 civic EX head gasket?? not sure if that will work then... i blew a headgasket in my HF motor, so i pulled the head off yesterday but im decdiding to just pull out the HF motor n finish the mini-me and have it in :) cant wait... 60hp to 130 will be a good jump lol
     
  15. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    You're playing with relatively low boost levels, so the head gasket isn't really that big of a deal. Use an OEM Z6 head gasket and you'll be fine. You can use a 96 EX metal gasket, but if it's the two layer version- you'll be running your compression about .3:1 higher. I don't know if you want that... but at your boost levels it won't matter too much.

    If you're putting in new bearings, then you're already building your engine the "right" way. If you have time, you might want to take an extra step and have your pistons ceramic coated- thermal barrier on top, and low friction on the skirts- that will let you run higher levels of boost while worrying less about detonation and melting pistons, and you'll make more power too. Having your rods shot peened at a machine shop will help to relieve any surface cracks or stresses on your stock rods too. These processes will probably cost you about $300 total, but it adds a measure of insurance to your engine build, and that can be a good thing later on. It's up to you. There are still plenty of people that make 200whp or more on the stock internals (no mods) without any issues- you just have to tune correctly.
     
  16. CRX2NR18

    CRX2NR18 Senior Member

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    well what should i do if i went with all motor? like if i decided to go all motor, what should my mods be, i mean i already ported the z6 head, got an i/h/e... i mean i dont know much about n/a haha... what about a y8 cam? adjustible cam gear too... i mean i know it proly isnt going to give me much... if any but those are just what im thinking... if i dont turbo i might no Nitrous, like a 35 shot just for a little more boost ya kno
     
  17. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    If you went all motor, I would use the DOHC ZC PM7 (or P29) pistons to get you up to 12.0:1 compression with the Z6 head. You can use the two layer gasket to take you out to 12.3:1. If you already have the head P&P for all motor, you should keep it that way- or have it P&P for a turbo.

    I would run the DOHC ZC pistons, have them coated, get the rods shot peened, buy a Crower stage 3 cam and valvetrain to match- then tune tune tune. A Y8 intake manifold can help you out too. I'll bet you could easily make 165whp on a good tune.

    The Y8 cam won't really change things much from the stock Z6 hardware. A cam gear will only allow you to move your power curve around- it won't allow you to change the overlap between intake and exhaust since you only have one cam. Go aftermarket on the cam and get a good cam gear.

    You can also play with the ratios on the transmission to get better acceleration- research the ratios and mix/match to get the best gearing for you.
     
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