Calling all 5MGE engine experts...

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  1. #1
    CelicaSupra.com Member rwhite's Avatar
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    Calling all 5MGE engine experts...

    I am in the middle of an engine rebuild on my 85 and I can't seem to find any good info on the 5MGE. I have done some measurements with a graduated cylinder and clay on the piston but I just wanted to check and see if anyone had these numbers or has done any measuring so we can compare numbers.

    Serviceable limit (How much material can I remove) on the Cylinder Head or Engine block? ( I have seen 0.006" for cylinder head, but that seems tiny)

    Piston Dish/Dome volume (measured about -1.5cc)

    Combustion Chamber volume (measured about 50cc)

    Factory gasket thickness (1.2mm or 0.047")

    Piston to valve clearance (measured between 0.110" exhaust and 0.105" intake and this was with a 1.4mm or 0.055" head gasket)

    These numbers are usually not that hard to find on other engines, but I guess that's what makes the 5MGE so special!
    1985 Toyota Supra

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  3. #2
    Prof. Honeydew CJSREDPRA's Avatar
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    Have you looked at the engine section of the online TSRM yet???
    Chris Eng
    1981 MA47 Silver Metallic 5ME Automatic
    1985 MA67 Super Deep Red 5MGE 5-speed
    Member PacNW Supras/Hidden Content from Popular Science
    Despite the constant physical and--judging by the twitchy, panicked expression--mental punishment inflicted on him by Dr. Bunsen Honeydew窶冱 experiments, Beaker keeps coming back for more. Clearly the Jackass crew grew up ingesting a healthy dose of these Muppet Show regulars.

  4. #3
    CelicaSupra.com Member rwhite's Avatar
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    Yeah, I have looked throught the EM section and the EM portion of the Service Specification section and I don't see any of the numbers that I am looking for. It does give some specs on warpage, but that seems to be about it for the cylinder head and the block surfaces.
    1985 Toyota Supra

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  6. #4
    CelicaSupra.com Member
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    84 mt 6mge with intake, exhaust, suspension, brake, and wheel mods
    85 mt 6mge stock

  7. #5
    Prof. Honeydew CJSREDPRA's Avatar
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    See previous post from him. No help here, he already looked.
    Chris Eng
    1981 MA47 Silver Metallic 5ME Automatic
    1985 MA67 Super Deep Red 5MGE 5-speed
    Member PacNW Supras/Hidden Content from Popular Science
    Despite the constant physical and--judging by the twitchy, panicked expression--mental punishment inflicted on him by Dr. Bunsen Honeydew窶冱 experiments, Beaker keeps coming back for more. Clearly the Jackass crew grew up ingesting a healthy dose of these Muppet Show regulars.

  8. #6
    CelicaSupra.com Member Dave A.'s Avatar
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    Sounds like you've figured out some of the "race engine" info. that's missing in the TSRM. :lol: Now all you/we need is the specs. for the stock valve timing and cam profiles. 8-)

  9. #7
    CelicaSupra.com Member rwhite's Avatar
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    Well, I wouldn't take any of the numbers I posted as exactly accurate. I am going to repeat the combustion chamber volume and piston dish/dome volume measurements so I can validate the first round of measurements. I am preparing the supra for scca ITS and there is a very detailed set of allowed engine modifications. The one I am working on at the moment is raising the comp. ratio by 0.5. I don't think it is going to take much to do that but I don't want to raise it more than the allowed amount and I also want to keep the valves from hitting the pistons. So if anyone else has any of the measurements it would validate my results.
    Last edited by rwhite; 04-21-2005 at 04:52 PM.
    1985 Toyota Supra

  10. #8
    CelicaSupra.com Member rwhite's Avatar
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    If anyone is interested, I repeated the combustion chamber volume and piston dish/dome volume measurements.

    Combustion Chamber Volume = 52 cc

    Piston Dish/Dome Volume = -3cc

    These numbers are for a stock 5mge.
    1985 Toyota Supra

  11. #9
    CelicaSupra.com Member supraz's Avatar
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    Hi Russell,

    I am very interested in these numbers.

    I have been measuring the intake manifold plenum volume, runner volume, head intake volume, head exhaust volume to see about how efficient the intake manifold is.

    I have been planning on measuring the combustion chamber volume, but have been busy with doing taxes.

    Unfortunately my engine seems to be the 8.8:1 motor so I won't be able to do a direct comparison. I don't think that the head combustion chamber shape/volume changed, but who knows.

    I've never cc'd an engine before, so I would like to know how you are measuring it.

    How have you been sealing the valves when cc'ing the head? How have you been sealing the rings when measuring the piston top volume?

    When measuring the piston/dome volume are you measuring with the rod/piston on the crank? I'm assuming that with the higher compression piston you have a significant pop-up so that the head may stick up above the block deck height. How do you handle this?

    On my 8.8:1 motor, the piston is almost a flat-top with valve relief cutouts and the gap between the piston and the combustion chamber wall down to the top ring being a positive volume. Without assembling the motor yet, I assume (that word again) that the piston stays below the block deck so that measuring the volume is not too hard.

    I'm not questioning how you're doing the measurements, I just want to be able to duplicate them.

    Regards,

    Dale

  12. #10
    CelicaSupra.com Member rwhite's Avatar
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    Dale,

    I learn something new everyday about the proper way to measure engine volumes, today I learned a recipe of ATF and mineral spirits is the best fluid to use....who knew. So my particular way may not be the best but it is getting more repeatable.

    Combustion Chamber:

    use the cam pulleys to actuate the valves out of the cylinder head
    take some grease and apply it to the valve seat (just enough to make a seal)
    actuate the valves back to their seats
    apply a ring of grease around the combustion chamber and place a piece of clear plexi glass over the combustion chamber
    the plexi glass needs a whole in it so you can add your fluid of choice (I used water with a little dish soap in it which breaks the surface tension)
    I use a 100cc or 100ml graduated cylinder to measure the fluid
    I start with the cylinder at 100cc and then subtract whatever is left over from 100 to get the volume of fluid that filled the combustion chamber

    I forgot to put grease on the valve seats last time I measured.

    The pistons on my 85 have a small dome and two valve reliefs.
    The piston flat portion is basically at zero deck, flush with the top of the block.

    To measure the piston dish/dome volume: (I still had the short block assembled)

    Move the piston about 2 inches into the bore
    apply a ring of grease around the bore just above the piston
    move the piston up so the rings catch the grease and create a seal
    I left my piston about 0.24" below the top of the block, that number doesn't really matter as long as you know it.
    then apply grease on the top of the block around the bore
    place the piece of plexi glass on top of it and make sure the grease seals to the plexi glass
    Use the graduated cylinder and find out how much volume you have

    Then use the 0.24" and the bore to calculate the volume of a cylinder (basically what it would be if you had a flat top piston)
    Then take your calculated volume minus your measured volume and you should have a good idea of the dish/dome volume.

    There are probably better ways to measure it, but this is how I found those numbers.
    1985 Toyota Supra

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