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Compression ratio questions

Discussion in 'The Garage' started by 88-383, Mar 13, 2006.

  1. 88-383

    88-383 1/2 ton status

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    Do you guys think 10.1 is to high for a K5? The enfine is built 355 with aluminum heads, full blueprinting and balance. I don't mind having to use high octane fuel, but i don't want it to blow up either.

    Kelvin
     
  2. 1977k5

    1977k5 3/4 ton status Vendor

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    With aluminum heads I think 10:1 would be just fine, but you will have to use premium fuel.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    What kind of heads besides aluminum?

    I think one rule of thumb states you can go a full point on compression with the same gas.

    I'm running 9.2:1 with 87, you probably can with AL heads @ 10:1 if they've got a good chamber.
     
  4. gauder

    gauder Banned

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    Especially okay if you can use small cc combustion chambers and flat-tops to achieve 10:1.
     
  5. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    stupid question.... how do you determine your compression ratio???? :crazy:
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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  7. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Oops, the previous poster already dealt with what I was going to post.
     
  8. 88-383

    88-383 1/2 ton status

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    I'm using the 195cc Trick Flow CNC heads on this engine. Normally I would've had the block zero decked, but some reason this time I didn't. Would you guys say it'd be ok even towing?

    KM
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Are these the Kenny Duttweiler models? I can't find the 195's on TFR's site, but I do see some 23* Kenny Duttweiler ones there.

    Looks like fast burn inspired chambers on the 175 non-Duttweiler models, so if the Duttweilers follow suit and are also fast burn, I would *suspect* (experience may prove otherwise) that you would be fine with 87 octane at that compression ratio.
     
  10. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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  11. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    yeah i dont know what im doing.. i came up with a 1.43 : 1 ratio!!! :haha:

    she should purr like a kitten
     
  12. 88-383

    88-383 1/2 ton status

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    Yup 195's you can see them here. Being able to run 87 octane would be a real bonus. I just wanted a sanity check because I don't want a pinging engine.
    http://www.trickflow.com/product/chevycylinderheads/23degree/pr_23degree.asp
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    What are your combustion chambers like? That's key to what kind of compression numbers you can expect to get away with, and that sight doesn't show on your 195's that I could find.

    If you are worried about it pinging on even super unleaded, I wouldn't worry at all. (just in case it does with 87 or 89)
     
  14. MTMike

    MTMike 1/2 ton status

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    The 195 is the intake runner volume, not the combustion chamber volume - more than likely your CC volume is either 64 or 70. They can be had in may other cc volumes depending on the mfr, but AFIAK 64 & 70 are the more common ones for small block Chevys.

    I'm running the Vortec heads on mine, and though I don't know the cc volume, they come in either 64 or 70. If it's got 64ci I'm pushing 10.48:1 (which sounds about right because it pings like a Diesel on anything less than 91 octane), or if it's got 70 I'm running 9.84:1.

    Mike
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, I understand the CC volume vs. runner volume, it's just that the sight doesn't show a pic of the combustion chamber design. :)

    The other heads pictures do have the fast burn (used in the Vortecs) chamber design, so that was where I was going with it..10:1, AL heads, and a fast burn chamber *should* be pretty easy on the fuel.
     
  16. tarussell

    tarussell 1/2 ton status

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    Don't forget about cam timing playing a role in different motors that are being compared with the same C/R ratio's . What works in one engine might not work as well in another .
    Tom
     

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