Timing chains

Discussion in 'Engine & Drivetrain' started by SnowDrifter, Oct 9, 2018.

  1. SnowDrifter

    SnowDrifter Full Access Member

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    Saw a post in the NNBS section where a member's engine skipped timing and pistons married valves.

    I'm curious, are these a failure point on the LM7s that it would be worth replacing as part of preventative maintenance?
     
  2. drakon543

    drakon543 Full Access Member

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    it probably is part of the pm cycle people just dont do it since it can be costly. also by the time its needed alot of the times the vehicle is on its second or third owner.
     
  3. CountryBoy19

    CountryBoy19 Full Access Member

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    I'm not sure on the LM7 but I have a 98 GMC with L31 (5.7 Vortec) that was having some issues. 3 different independent sources said, "have you replaced the timing chain just to make sure it's not causing that?"... So I did some reading, GM says (at least for the L31) that the timing chain is made to outlast the life of the engine. I decided to do the swap anyways. I bought an OE timing chain and sprocket kit and a new dorman cover. The old timing chain, with 330k miles on the engine, was actually slightly tighter than the new OE replacement... and the new timing chain didn't solve the problem, it was a waste of time and money...
     
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  4. drakon543

    drakon543 Full Access Member

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    the 5.7 is usually the distributor gear being worn out. that or moisture got in the cap. dealt with a couple that jumped a tooth prior to outlasting the engine lol. either way its still about how well you take care of it and how you drive it. drive it around like a normal person and do the maintenance as its supposed to be done and the chain with definitely outlast the engine.
     
  5. CountryBoy19

    CountryBoy19 Full Access Member

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    In my case the issue surfaced about 2 years/1200 miles (I don't drive it much) after I put a brand new distributor on it so it wasn't the distributor/cap/rotor... I even swapped it for a known, good distributor just to eliminate that as a culprit. I never did figure out the problem. Not to continue the thread-jack but it was telling me it was 1 tooth (26 deg.) off on the timing and it was kicking back when trying to start. It was fine up until that point then all of the sudden started acting up. Pulling the distributor and moving it over 1 gear tooth put it 26 degrees out the other way. After doing it several times, thinking I was somehow moving it 2 gear teeth I started to measure the rotor angle every time I pulled it to ensure I was ONLY moving it 1 gear tooth. After the timing chain replacement and still the same problem I said F**k it and ground out the hold-down fork on the distributor base so I could turn the distributor to time it, problem solved.
     
  6. Doubeleive

    Doubeleive Elite Member Supporting Member

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    I was told by the dealer that starting with the NBS trucks the timing chain never needs to be done, if one went out it must have been a freak thing or wrongly diagnosed.
     
  7. drakon543

    drakon543 Full Access Member

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    kinda hard to misdiagnose the alignment marks on the crank and cam being off but i geuss. not like most dealerships have a common nickname like stealership.
     
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  8. SnowDrifter

    SnowDrifter Full Access Member

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    Honestly that sounds right for doorman. They're an economy brand


    I'm a little skeptical of the lifetime of the engine bit. The amount of fine print I've seen with that word gives me pause.

    Kind of like the whole lifetime transmission fluid thing... It doesn't mean it's good forever. It means that by definition, when the transmission fails from shit fluid, then that's the lifetime, ignoring the bit where some TLC would get double or triple the lifespan out of it.

    Or the one where "lifetime" is the designed lifetime of the part. Ex 100k or 150k



    This being said, if timing chains are considered a fluke failure on these motors, I won't mess with unless I have the timing cover or oil pan off. If one comes off, so does the other. Gaskets interfere with each other and I reason if one's bad, the other's not far behind. And messing with one might cause a leak at the seam where they meet. That'll be when I do the "while I'm in there" stuff - oil pickup oring, timing chain(maybe? depends on how it looks when I inspect it), water pump, harmonic balancer, and maybe a volume oil pump like a melling 295hv. That bit's very much undecided as of yet though
     
  9. randeez

    randeez Full Access Member

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    havent heard of a timing chain going on an ls without being caused by something else...swap it if you ever have the front cover off but i wouldnt worry about it, theyre relatively cheap. ls2 should fit it, i see the "C5R" thrown around in high performance builds a lot but prob not needed. mine (later year) uses a tensioner on the timing chain
     
  10. CountryBoy19

    CountryBoy19 Full Access Member

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    I realize Dorman is a budget brand but I'm not sure what you mean by "that sounds about right"... The timing chain & sprockets were OE, as I mentioned. The reason the Dorman cover was chosen is because they actually offer design improvements over the OE cover that make it easier to replace without removing the oil pan as well.

    The distributor wasn't OE but it was quality brand. I always buy quality on parts that actually make a difference.
     

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