1JZ Head Gaskets And Compression Help / Advice

Thread in 'Technical Questions' started by e_dale2000, Nov 23, 2014.

  1. e_dale2000

    e_dale2000 Member

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    Hi,

    Ive got a Non VVTi 1JZ being rebuilt and forged standard they are 8:5:1 comp ratio and i want to get as close to 9:0:1 as possible. Ill be using 87mm CP Pistons to hopefully give me a 9:0:1 comp ratio. Im thinking of using either a 1.3mm or 1.5mm gasket.

    I know the 1.5mm will lower the compression slightly and i've been recommended running this as the engines gonna be seeing temps and boost with the HX35.

    Ive seen some Tomei head gaskets but there 87.5mm will this make a difference ? would the gasket need to be a 87mm?

    Ive been reading up on head gaskets and if your bore is 87mm generally there slightly bigger to accommodate but i cant find out if the Tomei gaskets include the squish area and advertise it or if it really even matters?

    if not what can people recommend for 1.3/1.5mm Gaskets for an 87mm bore.

    Hopefully someone can educate me

    thanks for your time!
     
  2. Stavros

    Stavros Active Member

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    I'm confused? What compression you actually want? I'd use pistons to go for the compression ratio you want, and not use different thickness HGs to change it, as that's a shitty way.

    Depending on cam spec, your dynamic compression (which is what matters, static is pretty meaningless) could be plenty low even at 9:1 anyhow.
     
  3. e_dale2000

    e_dale2000 Member

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    Hey dude sorry ive probably not worded it correctly, im gonna run cp pistons to give me the compression ratio I need but am unsure regarding head gaskets as im aware theres different types but I am wondering using 87mm pistons with an 87.5mm gasket would it make little to no difference? or whether im better sticking with a 87mm gasket?

    im aware all gaskets are a little larger than the bore to accommodate for the squish area but cant work out if the Tomei ones are just stating this or are generally bigger?

    I was recommended by my engine builder that 1.3mm would be fine but if im going to be running boost and getting it hot that I should use a 1.5mm gasket. I don't know how much difference this would make as it would lower the compression a little but probably not really that noticeable maybe to 8:8:1?
     
  4. Stavros

    Stavros Active Member

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    As I see. From what I gather, the .5 extra makes no odds.
    What cams are you running?
    What boost are you planning on?
     
  5. e_dale2000

    e_dale2000 Member

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    HKS 264s IN/EX with adjustable pulleys. prob a min of 1.5bar as the holsets don't start really working until then if I recall.
     

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