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Compression ratio help please.

Discussion in 'The Garage' started by SF87K5, Nov 27, 2004.

  1. SF87K5

    SF87K5 1/2 ton status

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    I am going to be putting new heads and roller cam in my 355 TBI soon. I want to run 9.1-9.5 compression in my engine. The heads I am getting are the World Products S/R Torquer heads and they only come in 76cc Combustion Chamber Volume. How do I go about figuring what size gasket I need to get the compression ratio I want.
    Any help or links the this info will be very helpful.
     
  2. Beast388

    Beast388 1/2 ton status

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    Danny.....check your e-mail. I just sent you a Microsoft Excel file that you can use to calculate your comp. ratio. You will need to know alot about your motor to make an accurate calculation. /forums/images/graemlins/waytogo.gif

    Oh and by the way...the S/R Torquers come in 58, 67, 72 & 76cc versions. /forums/images/graemlins/waytogo.gif
     
  3. POWERMAD

    POWERMAD 1/2 ton status

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    Here ya go. clicky
    Type in part# H618CP30
    9.38:1 compression with 76cc heads.
    Values are calculated with a virgin block 9.250" deck, .025" piston deck height and a .030" compressed head gasget.
    That would give a quench of .055".
    That is all ballpark figures, you would have to measure it all out to get the final ratio.
    Another click
    A good read on quench. click
    I have a set of Speed-pro's that I linked.
    Now that I have to use another block and it will be .030 over I am going with the flattop 2 valve releif version.
    8.68 with 76cc chambers, mine are prolly closer to 74 and I am going with a .050" quench. That should put me at 9's door. Which is what the cam I am going to use recomends.
    I have never tried to soup up a TBI plant but I would think that 9.0:1 would be plenty, if the sensor detects detonation it will retard the timing and it will run like crap, especialy with todays flavor of fuel.
    No need to build a plant that you can't take full advantage of.
    Besides just ditching the stock dish pistons for flattops will be a good upgrade.
    Read the clicky on quench and it goes into better detail on that.
     
  4. SF87K5

    SF87K5 1/2 ton status

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    Ben thanks for the e-mail, those are the only center bolt heads that world makes for 87 and up 350 sbc. I already called summit and jegs and the 76cc heads are it.

    Powermad Thanks for the info you posted it helped alot./forums/images/graemlins/thumb.gif I need to check with the guy I got my 355 from and find out what kind of pistons he had put it.
     

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