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Thread: shaved head

  1. #1
    CelicaSupra.com Member 4SFED's Avatar
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    shaved head

    I recently acquired a nonrunning '85 Supra that had been stored in a garage for twelve years. It came with a 5mge-in-a-basket. From the seller:

    "The motor is not installed. We did a full rebuilt on the motor years ago, and used the pistons and rods from another supra in the rebuild. We forgot to check the clearances, and managed to spin the bearings after starting it up. The donor motor had the larger, early model, con rods and we didn't plastigauge the bearings before installing everything. The motor was disassembled again, the crank checked and polished, and the right bearings ordered. We never reassembled the motor. Everything is there, labeled, and ready for reassembly except a head gasket kit will be needed. Motor is stock..."

    I told the seller that I didn't need the engine because I have a 6mge that needs freshening up that I'd like to put in. But he wanted everything gone so the motor-in-a-basket came with the car. All the motor parts look like they just came out of the machine shop. The pistons are the older low compression. I am leery to try to put together an engine that has failed twice already and I already have that 6m so I decided to use the fresh head from the basket case on my 6m. I bolted the cam belt cover on the front of the head a couple days ago and noticed that it protruded about 1/16" past the head surface so the head must have been decked and they neglected to cut the cam cover along with it. So if they hadn't spun the bearings on startup they would've had a major oil leak and/or head gasket failure, too.
    So I took the cover over to my friend's machine shop and he cut about .080" off to match the surface of the head.
    That's about 2mm they'd taken off this head.
    My questions: Is that too much for the 5/6m? Will the valves and pistons get along together? Will the cam timing be too far off? Will it need a head spacer shim along with the headgasket?
    Dave Harrison

    current lineup and year acquired:

    '85 white Mark2 7mgte 5sp 1990
    '85 white Mark2 7mgte Auto 2009
    '84 maroon Mark2 6mge 5sp 2013
    '86 red Mark2 7mgte 5sp 2016
    '85 black Mark2 6m Frankenmotor 5sp 2017

    Hidden Content Originally Posted by cheappower82 Hidden Content
    Guess you have the magic touch; touch mine please?!

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  3. #2
    CelicaSupra.com Member williamb82's Avatar
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    If the belt doesn't break, you shouldn't have a problem. Just be sure to rotate it by hand several times after the head is bolted on and the timing belt is installed correctly.
    william
    Hidden Content black 84 7mgte, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
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  4. #3
    CelicaSupra.com Member drjim's Avatar
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    You can always "clay" the pistons to positively measure the amount of clearance you have, but that requires "wasting" a head gasket.

    - Jim
    1985 5-speed "Ms. Swan"

    OH, What A Feeling!

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  6. #4
    CelicaSupra.com Member Khlause's Avatar
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    William and Jim nailed it; the only thing I would add is checking to see just how good a valve job they did on the head.

    You can check the valve grind with out the cam towers on the head:

    Aquire a can of carb clean or brake clean; spray this down the valve ports and check for leakage into the combustion chamber. Use liberally, a good valve grind will provide and air tight seal. If you have any leakage you will see moisture around the edges of the valve in the combustion chamber side of the head, some times valve jobs are so bad that there is actual dripping of liquid coming from the valve seat.

    If the valve job is bad, you can either have a quality machine shop fix it, or you can diagnose the issue your self.

    If you intend on diagnosing this your self, ask for help on the forum here or consult the internets, either works well.

    End of the story however should be; no valves leaking.

  7. #5
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    One thing you could also check is the total thickness of the head compared to the total thickness of another 5m head. Just need to find a good spot to measure from down to the deck. This is a good way to determine how much has been removed without relying on the front cover. I've machined many front covers and they often don't sit perfectly flush. I'd also be very surprised if a machine shop removed 080" off the head, that's 10 times the norm.

  8. #6
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    Sorry, meant to say that front covers often don't sit perfectly flush from the factory...they should sit flush prior to final assembly

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