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PDN(98-01 GX) vs. PM7/P29 Pistons

Discussion in 'Engine Building' started by K2e2vin, Oct 26, 2005.

  1. K2e2vin

    K2e2vin Senior Member

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    Ive tried searching but PDN is too short for the search engine. Anyways, which one will yeild a higher compression? Of all the threads I can find, I can only find dome height and compression height(PDN has a 1mm shorter dome but .5mm higher compression height than the PM7/P29s).

    Ive tried working backwards with the D-series calculators and got 4.7cc as the dome volume for the PDN. Is this right?
     
  2. K2e2vin

    K2e2vin Senior Member

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    *note: this is not hard fact; but rather info based on what I can find on other forums, compression calculators, etc.

    well after a shit-load of digging i found out the PM7/P29 pistons yield a little higher compression(but still very high for street engine). The compressions are high due to the fact they stick out of the block a little on the D15B block (14.23:1 vs the P29's 14.35:1) The PDNs stick out .5mm more than the P29s; but has a smaller dome(4.7 vs. 7.2).

    I can bring it down to ~12.7:1(PDN) or ~12.8(P29/PM7) using Mr. Gasket stackable head gasket. Now, these are very high compressions; but are they streetable on 93-octane with ITB's? Also, whats better to have; a higher compression height(PDN) or a bigger dome(P29/PM7)?
     
  3. reikoshea

    reikoshea HS Troll...And Mod Moderator VIP

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    12.8 is pushing it on pump...gonna need some serious spark plugs and wires to make it without detonation (thats the only reasonable thought ive got...other than that, your sol)
     
  4. K2e2vin

    K2e2vin Senior Member

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    yea its pretty high; i can get higher octane(100 octane) but that wouldnt be convenient because this is a daily driver.

    Ive heard of people using LS rods, so how about his: PMS(01-03 GX) Pistons, 2-layer HG, and with bushed GSR/ITR rods? i got an CR of 11.87:1 with that setup...
     
  5. reikoshea

    reikoshea HS Troll...And Mod Moderator VIP

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    i think that might be okay, but you still might get detonation without enough spark
     
  6. K2e2vin

    K2e2vin Senior Member

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    right now the motor has fresh NGK plugs and stock wires. I think it should work out ok because the stock GX motors have 12.5:1 compression stock, but in January its going to get MSD wires, MSD cap and external coil, iridium plugs, and maybe if i have more cash laying around, Crane HI-6 ignition.
     
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