Calling all 5MGE engine experts... - Page 3

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  1. #21
    CelicaSupra.com Member lil'devil's Avatar
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    I've got to go back to school to understand some of this stuff..HAHAHAHA....great info guys....

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  3. #22
    CelicaSupra.com Member rwhite's Avatar
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    Anyone come up with dish/dome volumes for their pistions yet?
    1985 Toyota Supra

  4. #23
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    given 5M-GE pistons and head (head same as 6M?) and stock gasket gives volume of 49cc with 6m/7m crank and rods this would give a CR of 9.878:1 AWESOME!!!!!

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  6. #24
    CelicaSupra.com Member ZZT231's Avatar
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    Well Allan, now you are going to have to rip the 6MGE open to see what pistons are in it now...

    *Want to keep tabs on this thread.

  7. #25
    CelicaSupra.com Member ddd228's Avatar
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    5MGE engine rebuild time

    Please Help This Guy!

  8. #26
    CelicaSupra.com Member
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    There should be some way to look/feel thru the plug hole to determine piston surface.
    84 mt 6mge with intake, exhaust, suspension, brake, and wheel mods
    85 mt 6mge stock

  9. #27
    CelicaSupra.com Member Dave A.'s Avatar
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    Quote Originally Posted by StanS
    There should be some way to look/feel thru the plug hole to determine piston surface.

    borescope

  10. #28
    CelicaSupra.com Member rwhite's Avatar
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    I have done some more measuring and have determined that about 51cc is the best measurement for the combustion chamber that I can come up with. The piston dish dome volume for the pistons currently living in my 85 is about 1.14cc (a combination of measuring the dish portion with fluid and calculating the dome with math/measurements) and that is added to the volume of the combustion chamber and gasket volume to get your Volume at TDC. When running through the rest of the calculations it appears that my current engine set up has a compression ratio of 8.7.....hmmmm. Well, if you change the gasket thickness to 1.2mm, which is supposed to be the stock gasket thickness, you end up with a cr or 8.84, which is just about right for the earlier 5mge’s.......hmmmm. This leads me down multiple paths:
    The crank offset/stroke for the 85's or the 5mge's with a cr of 9.2 is not the same as it is for the 5mge's with a cr of 8.8.
    The pistons I have are for an early 5mge.
    I can’t measure.

    Does anyone know if the crankshafts have different part numbers between the early and late 5mge’s, possibly relating to a different crank offset?
    Or, is the wrist pin set in a different location on the higher cr motors? Note: The flat portion of piston in my engine appear to be at zero deck at TDC, does this seem consistent.
    I guess the basic question is…..What exactly made the compression ratio go up from 8.8 to 9.2?
    1985 Toyota Supra

  11. #29
    POTATO Tanya's Avatar
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    Quote Originally Posted by rwhite
    .
    I guess the basic question is…..What exactly made the compression ratio go up from 8.8 to 9.2?
    I always assumed it was the dome of the piston...

    I've never torn apart an earlier model engine but here are pics of a 9.2:1 piston...




    I'm sorry, I didn't read everything...lol So is your engine a late model or earlier model 5M?
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  12. #30
    CelicaSupra.com Member rwhite's Avatar
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    Well, I called a Toyota dealership and it looks like:
    Crankshaft part number for 8/81 - 12/85 is 13411-45013 all the same

    Piston part number for 8/81 - 8/84 is 13101-43041
    8/84 - 12/85 is 13101-43051

    Connecting Rod part number for 8/81 -1/84 is 13201-45010 and 13201-49015
    1/84 - 12/85 is 13201-49026

    Cylinder Head part number for 12/81 - 12/85 11101-49296 and 11101-43031

    Of coarse the parts book has no technical info, but it seems the pistons and connecting rods are different before and after 84. If anyone has any tech info or corrections to this please let me know.
    1985 Toyota Supra

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