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Thread: Head Removed

  1. #1
    Registered User Weasel73240Z's Avatar
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    Default Head Removed

    So I took the head off of my 73 expecting to find a blown head gasket, or a crack in the head, which would explain the coolant in the head, and coming out of the exahust, when I got the car running a few weeks ago.

    And I found....nothing. The head gasket looked great, no blow-by that I could see. The cylinder head, at least what I could see (I haven't pulled the vales yet) looked great. No evidence of any cracks. The block looked great. However, I have the old wooden block holding my timing chain at TDC, so I can't see much of the piston walls. I straight edged the block and head, both seem very flat.

    I have to decide now whether to lose the timing chain block, and spin the motor so that I can inspect the block more thoroughly. I don't want to screw with the timing chain, so I was hoping not to remove the wooden block. I was really hoping to find a trashed head gasket to explain the coolant leakage, and finding nothing is really confusing. I had a lot of coolant in the head, and coming out of the exhaust. However, I didn't have any coolant in the oil pan when I drained it. Am I missing something? Should I just buy new gasket set, re-assemble, and hope that the head gasket was the problem?

    Anybody got any ideas?
    Paul Martin
    1973 240Z HLS30-127623 (10/72)
    4.11 R-180, 79 ZX 5-speed, ZX Distributor, ZTherapy SU's

  2. #2
    Registered User Weasel73240Z's Avatar
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    Default

    Also, when I pulled the head off, I noticed that the 1, 2 and 3 pistons look like I would expect (minor black carbon build-up), but the 4, 5 and 6 looked clean. I suspect that this is because they were being "washed" with coolant.

    I realized that since the 4, 5 and 6 are fed by a separate manifold/carb set-up, that I may be barking up the wrong tree altogther. Maybe the leakage isn't coming from the head or block, maybe its coming from the rear carb/intake assembly. Has anybody had experience with coolant leakage from the carbs getting into the motor?
    Paul Martin
    1973 240Z HLS30-127623 (10/72)
    4.11 R-180, 79 ZX 5-speed, ZX Distributor, ZTherapy SU's

  3. #3
    Biafra for President e_racer1999's Avatar
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    Default

    ^that migh be possible if the coolant line running through the intake manifold somehow got compromised. check your intake manifold for cracks, etc...
    Jason King
    6/72 240Z / HLS30 89646 (Yellow)
    1996 Infiniti I30 *I finally have all Nissans again!*
    1971 510 4door (wife's car)
    IZCC Member #14186

    Quote Originally Posted by xray View Post
    As unfortunate as it may be, if you want to vintage race, go Euro....If you want to race for real, stick with the Z!

  4. #4
    HLS30165540
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    Default

    What type of straight edge did you use on the head? You need one that will go from one end to the other AND be precise. Take it to a shop and have them use a precision straight edge and pressure test it.
    The 1973 240Z 165540 Slightly modified. L28, 5sp, cam, headers, MSD 6AL, power windows, power door locks, leather seats, custom this and custom that.

  5. #5
    Registered User Weasel73240Z's Avatar
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    Default

    I just got the head back from the shop. It was thoroughly inspected and crack checked, nothing. So they took it apart, cleaned it up, new valve guides, polished the ports, put it back together, and adjusted all of the valve lash. It looks like its brand new.

    If anyone is in Southeastern Massachusetts and needs a good engine shop, the name of the shop is Precision Engine, in Dighton, MA. If anyone needs more info, email me, and I'll get you their phone number. They did an awesome job, at a very reasonable price (around $400 total, with a complete new engine gasket kit and a few other minor things).

    The coolest thing was the guy knew what the head was as soon as I opened up the bed of my truck, just by looking at it, and he talked for about a 1/2 hour about how much he regretted selling his 240Z when he "was a kid". I knew right then that he would take good care of me.
    Paul Martin
    1973 240Z HLS30-127623 (10/72)
    4.11 R-180, 79 ZX 5-speed, ZX Distributor, ZTherapy SU's

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