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Exhaust smoke during start-up

Discussion in 'V8 Engine' started by eggbert68b, Jan 7, 2018.

  1. eggbert68b

    eggbert68b Member

    Hi Guys,

    This is likely to be addressed before but I couldn't find any related posts.

    My V8 in recent months has started to put out a lot of exhaust smoke for about 5 minutes following start up, despite being cold or warm (i.e. being run a short time before). The exhaust is neither splashy, white nor blueish, and smells like a rich mixture as if the choke has been left out (despite being in). After 5 mins the exhaust is clear and idle is a steady 750 rpm.

    The engine is in a good state of tune to my knowledge and idles and runs well and the plugs are the correct colour. The carbs are HIF6 and the engine is a 3.9 with all the necessaries such as Magnecor leads, electronic ignition, and 5-star fuel equivalent (using Tetraboost).

    Is this indicative of a carb issue or rings / piston issues. It gives the impression there is a large amount of unburnt fuel or very rich fuel which needs to be cleared initially.

    The car is a daily driver and so is used often.

    I am interested if this a common issue with other drivers.

  2. Penguin

    Penguin Member

    your symptoms do not suggest rings/bore/pistons they usually smoke under heavy load.
    is it using coolant? it could easily be coolant seeping into a cylinder when the engines turned off and burning off when you start up.
    otherwise the smoke you suggest is probably oil going down the valve guides
  3. eggbert68b

    eggbert68b Member

    Hi Penguin,
    Thanks for your reply . I had wondered about coolant but it smells of petrol / oil rather than a rather 'sweet' smell which I would expect coolant to smell like.

    The oil going down the valve guides is more likely. The burning question here then is this indicative of potential trouble in the future.
    thanks again, Simon
  4. GRTV8

    GRTV8 Well-Known Member

    Clean out your flame traps. Dont forget the one at the rear of the left rocker cover too.
  5. eggbert68b

    eggbert68b Member

    Yes, thats a good point. I actually only have the one gauze because I use the SD1 rocker covers and cylinder heads (with larger valves), suiting the slightly larger engine.
    Thinking on it more after posting the thread, it is likely to be the valve stem seals which were a common issue with the SD1 heads.

    It could be water vapour as the mix is poor with starting up but its only just started after 10 years since the rebuild.

    I guess my concern is if it will remain as is for sometime or progressively get worse.

    Its a an issue starting up in public places as it draw unwanted attention.

    Thanks again.
  6. unstable load

    unstable load Well-Known Member

    There is also a filter to allow air to enter the block, located at the left rear of the block looking from the front.
    It's on a small elbow that enters the rear of the block behind the tappet cover.
    Most people use a plastic inline fuel filter.
  7. eggbert68b

    eggbert68b Member

    Thanks all or your comments. I'll act on the above.

    My block doesn't have a crankcase breather given its a later 3.9 and so my engine resembles more closely the SD1 with the Vitesse heads and SD1 rocker covers and single flame trap. That said the breathing system will be reviewed.

    On reflection, its highly likely that its the valve stem oil seals, but the extent of which e.g. guides and valves as well is TBC.

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