What is this strange clanking sound in the engine ? | FerrariChat
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What is this strange clanking sound in the engine ?

Discussion in 'Technical Q&A' started by [email protected], Apr 17, 2010.

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  1. andy2175m4@yahoo.com

    [email protected] Formula Junior

    Dec 7, 2008
    473
    Los Angeles, CA
    Full Name:
    Andy Rein
    #1 [email protected], Apr 17, 2010
    Last edited: Apr 17, 2010
    What is this strange clanking sound in the engine ?

    I am converting the 308 from K jet to EFI, and it was running fine a few weeks ago, then I let it sit for a few weeks while I rebuilt the throttle body and rewired the EFI.

    Yesterday I went to start it, and now when I crank the starter, there is this loud clanking sound coming from inside the engine. Before cranking I disabled the fuel pump so it would not run. I made sure it would not start, as the clanking is very loud. It sounds like a small hammer tapping on the block. I checked the front bank, no busted rods.

    This clanking sound seems to be running at 4 times the camshaft speed and possibly 2 or 3 times the crankshaft speed.

    I searched all over the engine with the stethoscope and could not isolate the sound.

    I pulled the timing belt covers and front valve cover and could not see or hear anything unusual. I pulled the oil pan and could not see or hear anything.

    I put the stethoscope on the starter motor and could not hear anything unusual, but the high speed of the clank makes me think it's the starter drive gear, or something related to the starter, but still no clanking in the stethoscope when I put it on the starter motor.

    Anyone got ideas on what this fast, loud tapping noise is? I came out of nowhere after the car sat for several weeks on jack-stands, not running.

    I also put it gear, held the wheels, and stepped on the clutch, cranked the engine, and the noise persisted.

    TIA for your inputs.

    Andy
     
  2. eurogt4

    eurogt4 Karting

    Apr 15, 2006
    243
    Sacramento, CA
    Full Name:
    Mike
    #2 eurogt4, Apr 17, 2010
    On the theory that the last thing you worked on caused the trouble, it is very possible that a small part fell into the intake when working on the throttle body. Try pulling the plugs and see if one is all beat up.
     
  3. TheMayor

    TheMayor Ten Time F1 World Champ
    Rossa Subscribed

    Feb 11, 2008
    107,058
    Vegas baby
    #3 TheMayor, Apr 17, 2010
    Last edited: Apr 17, 2010
    +1. I had the same thought. What I would not do is turn the engine over anymore until you at least isolate if something is in a cylinder or not.

    Checking the plugs is a good way to start. If you see a damaged plug, you know what the story is. Popping the head may be the next step.

    But, given the seriousness of an engine noise, even if the plugs check out ok, I would also get a boroscope (or have a mechanic do it) and pull all the plugs to see inside the top of the cylinder and see if there is any damage. It will be very obvious if it's there.

    If there is no damage inside the piston, then you can check compression. If compression is OK, then you know it's somewhere else than the valves.

    Big rule of thumb... NEVER ASSUME. Find out first, then fix it.


    Good luck. I hope it works out.
     
  4. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    29,257
    socal
    #4 fatbillybob, Apr 17, 2010
    Andy,

    I'm in RPV by los verdes golf course. If you are RHE maybe I could come by and give a listen or can you post the noise in a sound file or with your video recorder and up load to youtube?
     
  5. andy2175m4@yahoo.com

    [email protected] Formula Junior

    Dec 7, 2008
    473
    Los Angeles, CA
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    Andy Rein
    #5 [email protected], Apr 18, 2010
    I found the problem, exhaust cam timing belt jumped two teeth, I adjusted the belt and the noise is gone....how did it jump 2 teeth sitting on jackstands in the garage (not running) for 4 weeks ? I will never know. I will now check compression and hope for no bent valves.
     
  6. 2NA

    2NA F1 World Champ
    Consultant Owner Professional Ferrari Technician

    Dec 29, 2006
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    Twin Cities
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    Tim Keseluk
    #6 2NA, Apr 18, 2010
    Huh?
     
  7. the_stig

    the_stig F1 Rookie

    Sep 19, 2005
    3,497
    #7 the_stig, Apr 18, 2010
    Could only see that happening if it was rotated backwards and even then it would be a little weird. How did you determine that it jumped 2 teeth? Meaning are you sure that it wasn't that way previously?
     
  8. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    29,257
    socal
    #8 fatbillybob, Apr 18, 2010
    If you need a hand I got leakdown tester and 36mm socket. What you are saying does not make a lot of sense. Your statements are mean dire consequences. Were belts recently done or long overdue? How could you do a FI conversion/programing on a car that was not timed right? Don't you need to program FI units today like doing a tec 2 or motec conversion? Is that what you did?
     
  9. vinuneuro

    vinuneuro F1 Rookie

    May 6, 2007
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    Vig
    #9 vinuneuro, Apr 18, 2010
    Check the tensioner. I've had a t-belt skip a few teeth upon start-up and bend all exhaust valves (non-Ferrari).
     
  10. andy2175m4@yahoo.com

    [email protected] Formula Junior

    Dec 7, 2008
    473
    Los Angeles, CA
    Full Name:
    Andy Rein
    #10 [email protected], Apr 19, 2010
    The belt on the rear bank exhaust cam jumped 2 teeth, I pulled the valve cover and checked the timing marks on the cams and the block and saw that the belt did move. The belts were timed correctly last time I reassembled it. Can't say how it jumped 2 teeth, but it did. Last time I ran the engine (after the EFI conversion) 4-6 weeks ago, it ran fine. No noise.

    Maybe the belt tensioner hiccuped and the belt jumped ?

    I moved the belt back to where it should be, and the noise was gone.

    I checked the compression, no bent valves.

    A mystery, yes, but nothing is broken.

    The belts are not new, maybe I did rotate the engine backwards. Must be time for new belts....(I see no broken or missing teeth on the belt either, still a mystery)

    My EFI setup is a Holley 950 EFI computer, GM engine sensors, oxygen sensor, 8 ea 24 lb injectors, stock throttle body, stock fuel pump, 42 psi regulator, works fine.

    The Marelli ignition still works, but when that craps out, it will be replaced by a Ford TFI solid state distributor and ignition.
     
  11. FandLcars

    FandLcars F1 Rookie

    Aug 6, 2006
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    Tempe, Az
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    Rick Schumm
    #11 FandLcars, Apr 19, 2010
    Hi Andy - I'm not sure the warning bells are coming through clearly enough in this thread, but I'm sure most would agree that you should not start your car again until you find why the belt jumped.

    If it happened once, it will surely happen again, and you may not be so lucky next time. You have a problem, and it needs to be fixed before your engine is damaged. I'd suggest replacing all belt tensioners (sorry, don't recall 308 details) and the belt, before I'd consider starting the car again. Best of luck on your car!
     
  12. zeiglerr

    zeiglerr Karting

    Oct 23, 2009
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    Lansdale, PA
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    Reid Z.
    #12 zeiglerr, Apr 19, 2010
    I had an intermittant chip failure one time that would make the ignition so far advanced that the engine would kick backwards on startup and brake the nose off of starters. It happened 4 or 5 times before it was finally diagnosed and fixed (after the dealer assumed that all of the starters were bad). Going on the theory that the last thing touched before the problem occured is the likely culprit - all else being normal - I'd be very suspicious of your FI mods and timing, and it seems to me that, even putting the timing belt back where it belongs, you have a grenade with the pin pulled out.
     

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