425 Challenges

Discussion in ''Da Nailhead' started by funkyriv, Jan 16, 2015.

  1. funkyriv

    funkyriv Well-Known Member

    The riviera stopped running before Christmas, and I finally got a chance to look into why last weekend. Wasn't getting spark, so I thought it might be an easy fix with a coil, etc. Coil tested ok out of the car. Pulled distributor cap and noticed it wasn't rotating when turning crank pulley. Pulled distributor out of engine block and gear pin was sheared. Checked the oil pump shaft for rotation, and it was seized.

    So, dropped the oil pan (painful to get that out!) and pulled out the oil pump. Idler shaft shattered the pump housing seizing the gears. In the bottom of the oil pan I also found lots of plastic fragments from the cam timing gear and one broken crank journal bolt that came from the #1 crank journal. This bolt sheared across the cap-journal joint. Fortunately the #1 crank journal surface looks excellent, other 4 caps are tight, and all rod caps are in good shape. The #1 journal bearing should probably be replaced, though. Pulling the pan shows me the front cover needs to come off for replacement of timing gears and chain.

    Why would a bolt on a main journal cap shear across the block-cap joint? Does this problem indicate that the block-cap bolt holes are not correct alignment or cap machining not square from original machining in Flint, MI? I have no clue when this bolt broke. Stuff happens 49 year-old cars.

    Thanks!
     
  2. 8ad-f85

    8ad-f85 Well-Known Member

    This will be something to contemplate while you completely go through your engine.:)
    The caps are not perfectly machined. Tapped holes aren't always perfectly aligned.
    Without a pic I'm picturing the bolt breaking at a thin spot, just below the shank.
    I've seen run-on break maincaps, I bet breaking bolts is more rare.
     
  3. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA


    Its looking less and less rare, just a couple months ago someone with a sbb 350 had a broken main cap bolt.



    Derek
     
  4. 8ad-f85

    8ad-f85 Well-Known Member

    Just a guess...bolt issue. They can be overtorqued a ways, they will stretch and leave a permanent thin spot.
    Some big diesel stuff shows inspections at the bolt shank for permanent deformation.
    Are these 300m material like other GM's?
    I've heard of bolt or assembly breakage at a Dana rear factory from assembly before the casting "settles". Sometimes they would "tink" in the morning.

    I dislike cluttering up a thread with conjecture, but things really have to move around to break a bolt.
    Misalignment is a problem, I just don't see much failure from it. You think there would be some signs of cap fretting or other telltales.
    Not going to be able to guess based on written description alone.


    The other failures at the top of the page are "train wreck" from planned obsolescence, timing gear.
     
  5. Schurkey

    Schurkey Silver Level contributor

    The lucky thing here is that the oil pump failure instantly caused the distributor to stop turning, therefore the engine didn't run with no oil pressure.

    I'd clean out the fragments including the failed bolt, inspect the cap/block mating surfaces, and if they're OK, I'd replace the bolt and the timing set and the roll-pin, and see what happens.

    Oh, yeah. Check all the valve stem seals to assure they aren't part of the plastic confetti in the oil pan. Now would be a good time to replace them.
     
  6. whatever

    whatever Well-Known Member

    I'd also check the harmonic balancer, whether it's still alive.
     
  7. Babeola

    Babeola Well-Known Member

    There would be some heavy duty vibration if the flexplate/flywheel were in any of the other five positions that will fit but are out of balance. Vibration can do a lot of funny things over time! My money is on that horse.

    Cheryl :)
     
  8. 8ad-f85

    8ad-f85 Well-Known Member

    :gp::gp:

    Definitely true...I assume people notice those signs.
     
  9. Babeola

    Babeola Well-Known Member

    How many one owner 66 rivs are you aware of? Many things can transpire with previous owners that the current owner inherits without knowing.
     
  10. 8ad-f85

    8ad-f85 Well-Known Member

    Understandable on any 40+ year old vehicle.
    Those type of vibration problems are not specific to vehicle types or even engine types, so it's silly to think it's exclusive to 66 riv's.
    Sometimes people patch up irreversible damage and dump them.
    The OP might not find a flexplate indexed incorrectly or a bad dampner because it may already have been "fixed".

    I'm dealing with a '66 Buick right now that is owned by the daughter of the 2nd owner, purchased 5 (?) years from new.
    It was always pathetically slow. The original owner had replaced one head from overheating.
    Current owner was surprised to see every piston with the tops nearly ripped off from ring butting, and all but 2 top rings broken.
    Had to show them.
    Their hearts were set on re-using the pistons....:Dou:. They insist that it was never overheated, so I allowed them to argue with the pistons.

    It's usually better to completely go through them rather than give them the minimum. 49 years is a LONG time for things to happen.
    When they are coming up to the end of a production run, I can see parts originally rejected being used...

    I mentioned noticing a vibration problem not to be a smartmouth...it suggests being driven with a broken bolt as long as it was owned if it were "fixed" prior to ownership. That would be unlikely.
     
    Last edited: Jan 17, 2015
  11. lapham3@aol.com

    lapham3@aol.com Well-Known Member

    I'd pull the engine and go thru it=check everything and replace whats indicated-good luck
     
  12. funkyriv

    funkyriv Well-Known Member

    thanks for the suggestions. after running a 1/2-course tap through the block threads, the cap and bolts line-up nicely so doesn't appear to be an alignment issue. i've had the car 7 years and never noticed significant vibration; balancer and flexplate look good. i think the bolt was over-torqued at some point, but i don't have proof that is true or any idea when it would have happened.

    not much to show with pictures that wasn't described above. broken bolt.

    putting everything back together, so the car isn't in pieces; i'll pull the engine and go through it in the near future.
     
  13. John Codman

    John Codman Platinum Level Contributor

    In an aircraft, this would be called a "sudden stoppage" and there are required inspections/part replacements that are engine-specific that must be made prior to further flight. One thing that is always required is that all rod bolts be replaced. If the big Nailhead were in an aircraft, I am positive that the timing chain and gears would be on the list. So would the oil pump rotating parts and the distributor gear and shaft. The harmonic balancer would be inspected/replaced, and the flywheel/flexplate bolts. Essentially, anything that would be significantly stressed by a sudden stoppage. Since the crank is forged, if it isn't broken, it's probably OK. Not necessarily true of the camshaft though.
     
  14. 8ad-f85

    8ad-f85 Well-Known Member

    Not necessary, but you could measure the bolt shank to get your answer on over torque.
    Should be permanently thinner near the failure.
    I bet with some searching you could find some specs on deformation.

    Google search, inspecting bolts for overtorque.
    This is the first one I found, there are likely many others.
    If you hover the picture it gives an explanation of failure.
    http://www.surescreen.com/scientifics/library-of-failures.php?p=30

    I've personally seen someone that was setting their torque wrench either 10 or 20 lbs too high and several of their engine builds. Never a bolt failure. Plenty of other problems, though.
     
  15. Schurkey

    Schurkey Silver Level contributor

    How is this--losing ignition due to failed distributor gear roll-pin--any more sudden than turning the key off?

    Landing-gear failure: Spinning propeller hits the ground = sudden stop.

    Engine loses spark = no big deal. (except at altitude, of course.)
     
  16. John Codman

    John Codman Platinum Level Contributor

    It is true that you didn't say that it was a sudden stoppage, I jumped to the conclusion that it was due to the shattered oil pump (It sure as hell was a sudden stoppage for the pump and distributor), I can't think of any reason for the broken roll pin to take out the oil pump. The pump must have eaten something to lock it up and take out the gear pin. Perhaps the bearing journal capscrew failure was an unrelated issue. After thinking about it some more, My guess is that somehow the oil pump ate a chunk of the nylon timing gear and stopped. Weird things happen. I once found a broken crankshaft in a 318 Mopar. It ran beautifully, but had a significant engine rap.
     
  17. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    Stupid stuff happens all of the time. My ex mother-in-law bought an '84 Jeep Cherokee in the mid '90s with a remanufactured long block (2.8L V-6 Chevy). Sounds good so far. The previous owner had all receipts. She drove it about 150 miles two days after purchase and lost nearly all of the oil pan bolts, most of the oil, and an engine mount along the way and had to return on a roll off. Naturally I was asked to help find out what was wrong. Nearly all of the engine's bolts were loose.
    I did a little research and found out that the reman engine was a later model ('88?) year that the rebuilder assured the previous owner would work, as long as they installed an electric fuel pump. Well, the original engine was externally balanced and the reman replacement internally balanced and it was bolted up to the ext balanced flexplate and balancer. Further research showed that there were no internally balanced flexplates to be found that worked with a Chevy V-6 and a Chrysler auto trans.
    Fortunately for my ex mother-in-law, the previous owner worked with the reman outfit (a big operation at the time) to get the correct year long block delivered to us no charge and I swapped the components and R&R the engine for her. The reman outfit then picked up the incorrect long block. They didn't pay for the engine mounts, however.
     
  18. funkyriv

    funkyriv Well-Known Member

    Russ Martin mentions a few weaknesses of the NH on his website, and recommends that these be addressed soon for engines seeing use. One of these is idler gear shaft working its way out of oil pump housing to the point of collision with rear crank counter weight. This is exactly the cause of my destroyed oil pump that siezed, which then sheared distributor gear pin and shut-down the engine before lack of oil pressure could kill anything else. When I pulled the oil pump out, the idler shaft was protruding significantly out of the pump housing and the shattered pump housing happened at idler shaft. Scuff marks lining up with idler shaft were seen on the outer edge of the crank counter weight. 2nd item on his list of potential problems... camshaft timing gear. Plastic in the bottom of my oil pan is direct evidence that my NH doesn't have much time left before this occurs. If the timing gear or chain break, the potential for serious damage is far more likely than the oil pump because pistons and valves can collide.
     
  19. Schurkey

    Schurkey Silver Level contributor

    Well, there ya go. The loyal old oil pump saw that there was going to be real engine damage--soon--from the about-to-fail timing set and missing main cap bolt, so the oil pump took one for the team, sheared the distributor roll pin, and got you inside the engine before the expensive stuff happened.

    Way to go, Nailhead Oil Pump. You won't be forgotten. Thanks for your sacrifice!
     
  20. whatever

    whatever Well-Known Member

    Mine was half way out, so it's somewhat common.
     

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