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Thread: 73S smokes on startup

  1. #1
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    73S smokes on startup

    Engine was recently rebuilt by supposedly a good mechanic. I'm looking to purchase this car. BUT, it smokes, all the time. Not a ton, but also enough to be worried about. What could one suspect it is? Rings, valve guides, way too rich, MFI problem, some sensor problem? Engine runs fairly well and it is, BTW the original 2.4S MFI engine that came with the car. SO, what are your bets on? TIA
    scott kinder
    kindersport@gmail.com

    Registry #614

    9110220587 - 1973 RSR revival in progress
    My Car Thread: "Five-Eighty-Seven..."
    “If it isn't there, it didn't cost anything, it doesn't weigh anything and can't break." - From the philosophy of Grady Clay

  2. #2
    Moderator Chuck Miller's Avatar
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    A couple of rules of thumb:

    Blue smoke = oil
    Black smoke = fuel

    Blue smoke on acceleration = rings
    Blue smoke on deceleration = guides

    Black smoke on idle and acceleration = rich mixture

    There is many exceptions to these rules, but this might get ya in the ballpark

    The thing is that most boxer motors make a little smoke on startup because of the oil vs. gravity deal…

    However, if this car is smoking out of the exhaust, blue smoke, all the time … even just a little… it needs work...

    Hope this helps
    Chuck Miller
    Creative Advisor/Message Board Moderator - Early 911S Registry #109
    R Gruppe #88

    TYP901 #62
    '73S cpe #1099 - Matched # 2.7/9.5 RS spec rebuild
    '67 Malibu 327 spt cpe - Period 350 Rebuild

    ’98 Chevy S-10 – Utility
    ’15 GTI – Commuter

  3. #3
    It's not uncommon for a fresh rebuild to smoke until the rings have broken in. So the question is how many miles does it have since the rebuild? Also, has it been broken in properly? i.e. driven at a wide range of RPM's. It's bad to let a new motor idle at one RPM.

    In a break in a motor should be given regular old 30 wt oil and drivin at various RPM's (city driving) for about 300 miles. Promptly change the oil and continue for another 1000 miles and change to a good multigrade oil. The numbers on this vary depending who you ask. Ask a good motor builder on the proceedure he recommends. I'm by no means an expert.

    I would get as much info as you can on the rebuild and have a "good" mechanic check it out (compression test,etc.). If it doesn't add up and needs another rebuild then price accordingly.

    Also, I just remembered. If the compression checks out and the motor is healthy... an overfill of oil can send oil into the intake causing smoking as well as a muffler that has been on an unhealthy motor and has oil residual in it.

    The oily muffler is a situation that had me baffled (pun intended) for a while on my Coupe. I had put on a used muffler and the car would smoke from residual oil left in it from an unhealthy motor.
    Bobby
    71' Olive 2.2E Targa / Early S #491

    I've always considered the glass to be half full...that is until I reached middle age and realized that it is actually half empty.

  4. #4
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    The owner had this to say:

    "The smoke is oil smoke-dark gray color I guess. If driven regularly, it always smokes some when you first start it, which is normal for that style of motor. It will smoke when you accelerate and a little while idling. If you let it sit for any length of time, say a week, it will smoke a lot more while idling until it burns all the oil out. If driven everyday it will burn about a quart of oil every hundred and fifty to two hundred miles or so."

    I would venture to guess that the rings did not seat correctly. I am not a tech expert (yet-just haven't gotten to fiddle around), but I've heard stuff about mechanics messing up the installation of the rocker arms and this kind of crap happens. I was thinking about the muffler too, but I think it's the original. The car is pennies, really it is, so I think I'll just tear it on down and do what I have to do. There's also a lot of other stuff that needs work. It sounds like fun fun fun to me! Thanks everyone-I'll be posting as I do the work on it's progress, etc. if and when I buy it.
    scott kinder
    kindersport@gmail.com

    Registry #614

    9110220587 - 1973 RSR revival in progress
    My Car Thread: "Five-Eighty-Seven..."
    “If it isn't there, it didn't cost anything, it doesn't weigh anything and can't break." - From the philosophy of Grady Clay

  5. #5
    "The smoke is oil smoke-dark gray color I guess. If driven regularly, it always smokes some when you first start it, which is normal for that style of motor.
    What style of motor would that be?

    Maybe one that either hasn't been rebuilt.

    or

    has been rebuilt wrong

    or

    was not broken in properly.

    Take your pick.

    it will burn about a quart of oil every hundred and fifty to two hundred miles or so."
    Rebuild time.

    The bad rings would show up upon acceleration. Smoke while idling or decelerating says valve guides.

    It's funny how some people can put on a new set of gaskets to stop the oil leaks and have the balls to call it a rebuild.

    Deduct $8500 for a rebuild.
    Bobby
    71' Olive 2.2E Targa / Early S #491

    I've always considered the glass to be half full...that is until I reached middle age and realized that it is actually half empty.

  6. #6
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    If I deducted $8500 for a rebuild he would have to pay to buy his car!
    scott kinder
    kindersport@gmail.com

    Registry #614

    9110220587 - 1973 RSR revival in progress
    My Car Thread: "Five-Eighty-Seven..."
    “If it isn't there, it didn't cost anything, it doesn't weigh anything and can't break." - From the philosophy of Grady Clay

  7. #7
    If that's the case and the chassis is in good shape i.e. not rotted and everything on the car is original then I think you should go for it.

    It'll cost you as much when your all said and done restoring it as it would have been buying one that's been restored but you'll have the pleasure of the process (if your a nut case like me) and it will be to your specification.

    Also, the value of the car will only go up over the years.
    Bobby
    71' Olive 2.2E Targa / Early S #491

    I've always considered the glass to be half full...that is until I reached middle age and realized that it is actually half empty.

  8. #8
    Lots of cars smoke on startup if they have been sitting. Heck, I drove a new '02 back in October that had been sitting at the dealership for a couple of weeks since it had last been run. It puffed a little and then cleared. Horizontally opposed engines are allowed to do this. If you want to see a real smoker, try a BMW K-Bike left on the *sidestand* for too long. Real mosquito killer.
    If it continues then it is a problem. A little at startup has never bothered me as long as it cleared.

    Chuck's notes are 100% correct as well.

    Good luck.

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