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Thread: Scary Random Engine Clank/Tap

  1. #1
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    Scary Random Engine Clank/Tap

    So I just bought a 1973.5 coupe with 118k miles or original miles. After a good clean up of tank and lines, fresh oil I got it started, but it makes an intermittent sound like a small hammer tap/clank on the case, but only on deceleration and idle. At a steady rpm it sounds perfect, its only when I let off or at idle it makes the random loud clank sound every 2-10 seconds.I am looking forward to doing a rebuild, but was also kind of hoping that it's something to do with cam chains so I can upgrade and drive in the spring when roads are salt-free and get to know the old tired engine before rebuilding. I took the cam chain covers off hoping to see an obvious explanation. I have read all threads but can't say for sure what I see. I think the left side looks stretched because of the smallish gap between idler arm and housing? It does not take a lot of force to deflect the chain 1/4". Also left tensioner piston looks more extended and possibly near end of travel. Any input from experienced eyes would be greatly appreciated!! thanks

    ps. I have video of first start and clank but its 4 min long and figured too long
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    Member #3896
    1973.5 911 T
    1974 911
    1974 CB750K

  2. #2
    Member #226 R Gruppe Life Member #147
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    Let me be the first to say, replace chain ramps. Just to get going if you want, update idler arms and tensioners, confirm cam timing, if noises are gone drive it.

  3. #3
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    Upgrading Tensioners For Sure

    Quote Originally Posted by gled49 View Post
    Let me be the first to say, replace chain ramps. Just to get going if you want, update idler arms and tensioners, confirm cam timing, if noises are gone drive it.
    I was going To do the OEM Carrera upgrade even though it was more expensive Because I have been punished by not using OEM parts in engines before. But if the experts here say that the Pelican upgrade kit that is SEBRO brand is good enough I just might do that instead And save 800 bucks. Also it looks like the OEM option does not have a link chain so could not be done with the engine in place. Any opinions appreciated. thank you
    Member #3896
    1973.5 911 T
    1974 911
    1974 CB750K

  4. #4
    You don't need to replace the chains at this point,,,,you must do those rubber chain guides, use the Carrera tensioners if you want, and the updated idler arms Gordon mentioned, verify cam timing and that should be all you need. I'd reuse the original chain sprockets,,,there seems to be some question currently on the Sebro replacements.
    Early S Registry member #90
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  5. #5
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    Does it sound like this?

    https://m.youtube.com/watch?v=fN4IU8awYK0

    If so yeah probably a bad chain tensioner. That’s what mine was. If you can push down on the tensioner with your hand I think it means it’s bad. I put in all new ramps and sprockets and did the carrera upgrade tensioners. Problem solved and been running 3 years or so no problems.
    Early 911S Registry#3437
    1971 911E

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    subscribed

  7. #7
    Member #226 R Gruppe Life Member #147
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    I’m with Ed, don’t use any new Sebro chain sprockets!

  8. #8
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    I had the unfortunate incident back in 1990 where the tensioner failed on one side. It caused a few bent valves on that side. My mechanic at the time put in the Carrera tensioners with new chains, along with doing both heads, valve guides and valves.
    Car has run well. I am now comfortable working on the engine myself, having rebuilt a 1986 engine. I have the original engine pulled and will break it down in a few months to go through it and refresh anything out of tolerance. I am curious to see how the chain and timing gears look, and replace the chain ramps if they were not done.
    Hopefully, no damage was done to your engine.
    E Sully
    1973.5 911T

  9. #9
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    Quote Originally Posted by edmayo View Post
    You don't need to replace the chains at this point,,,,you must do those rubber chain guides, use the Carrera tensioners if you want, and the updated idler arms Gordon mentioned, verify cam timing and that should be all you need. I'd reuse the original chain sprockets,,,there seems to be some question currently on the Sebro replacements.
    I am re-reading these realizing your are saying that I should replace the ramps during my interim fix with the engine in the car. I am not able to replace all the ramps with the engine in place am I? And so I can learn, why don’t you think the chain is Not stretched/too long? My know-nothing theory was that the left chain tensioner was at the end of it’s travel. Many thanks! I am doing what you guys say no matter what, just want to learn the whys. Thanks!!
    Member #3896
    1973.5 911 T
    1974 911
    1974 CB750K

  10. #10
    Member #226 R Gruppe Life Member #147
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    I think the chains are ok too. All the ramps can be changed in the car. You might have to support the engine and take off rear engine console and cross bar, but change the ramps, I’ve seen an end brake off go down in the engine and break the crankcase. The ramps go in a specific way, long end points to closest sprocket, do your homework.

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