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Trust bearing wear in a 2F????

Discussion in '40- & 55-Series Tech' started by crewzerdog, Feb 19, 2003.

  1. crewzerdog

    crewzerdog

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    Seems like I have a lot of play in the crankshaft of a 1979 2F engine - approx 2 mm. Have been told the thrust bearing is the problem (very worn) and the full main bearing set should be replaced. Only has about 12K miles on engine rebuild done by previous owner (rebuild actually done by Yamato Engines in Washington State - they are now a Jasper owned shop). Any suggestions on what could have caused the excessive wear on the thrust bearing? It appears to be worn on the back side (clutch side) of the bearing. Also, is it reasonable/adviseable to just replace the four main bearings and not the connecting rod bearings at the same time? I have the engine on a stand as I'm doing a frame off restoration - I'm detailing the engine now - all bead blasted parts and new gaskets all around. Any suggestions/advice would be helpful
     
  2. FJAfrica

    FJAfrica

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    although I have never encountered this before, the only real force behind the engine is the clutch. Maybe the throwout bearing is sticking to the shaft, causing more force than usual to be transmitted along the crank.
     
  3. toddslater

    toddslater SILVER Star

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    Since you have it on the stand, now is the time to make things as right as can be. Pull the crank and send it to a reliable machine shop and have it mic'd/checked out. It may need to be reground to to bring it in line. Obviously, renew all the bearings to match whatever has or has not been done to the crank. My .02.
     
  4. theo

    theo

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    If the rod bearings are fine it shouldn't be a problem to reuse them. But Todd is right. Have a machinist measure the journals first. And let him inspect your main and rod bearings too. Cheap insurance.
     
  5. Erics75

    Erics75

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    You could use plastigage to check your clearences but definitely change your thrust bearing and check end play. I also would have to agree with Todd, you have it out, take it apart and check everything.
     
  6. Pin_Head

    Pin_Head

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    The wear you describe is unusual and if you cannot explain it by the condition of the thrust surface of the crank, take the con rods and pistons into the machine shop and have them checked for straightness.
     
  7. crewzerdog

    crewzerdog

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    Thanks folks - looks like the jury has reached a verdict - my project truck needs some new parts - the previous owner spent $2700 (yeah, that's no typo) on the engine rebuild - including new piston, valves, etc. So, I'm pretty confident that stuff is "OK" but the main bearings (and thrust) will definitely be replaced. Still can't understand why the rear side of the thrust bearing is worn - if the clutch or throw out bearing were "pushing" the crank forward I'd expect the front of the thrust to have worn not the rear?? Anyway, I had hoped not to have to pull the crank but you guys have convinced me to "do it right" and get it checked by a pro. Maybe the rear side of the journal is "off" causing the weird wear characteristics. The cost of the rod-bearings are small potatoes compared to having to do this again after its back in the truck. Any suggestions on "best" places to buy or brand of bearings is appreciated.

    Thanks again for the help to this "newbie"
    Tom. 79FJ40
     
  8. Pin_Head

    Pin_Head

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    A bent rod will kick the crank to the rear every time it fires.
     
  9. toddslater

    toddslater SILVER Star

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    Pin,
    A bent, twisted rod would show lots of wear on it's respective rod bearing. Wouldn't that be more pronounced than on the thrust bearing ? Also crewzerdog, as I recall I think you may be about at your end play limit (3mm comes to mind). After you have your crank checked out and given the green light and renew all your bearings, your end play should improve somewhat.
     
  10. Pin_Head

    Pin_Head

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    No, not necessarily. It is mighty peculiar wear in the fact that it is only wearing the rear face of the thrust bearing. It is not a good idea to just replace the bearings without ruling out all possible sources for this. You will be facing the same job again in 2,000 miles. Machine shops have a machine for checking and resizing rods and it is cheap. Personally I would take the crank out and have it checked too and have everything remachined if necessary.
     
  11. crewzerdog

    crewzerdog

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    UPDATE - have pulled the crank and bad news! :( Thrust bearing so worn on the back side that it has eaten into the crank journal - yeah, new crank is on my shopping list now. Found other problems as well -- the two front main bearings are 'sloppy' - and rear rod bearing started to show some scoring (this maybe from 'contamination' coming off the thrust bearing??) I'm having the block line-bored and will replace with a new reground crank and full set of main & rod bearings. Thanks again to all for the great advice - I would have definitely regretted not fixing this the right way.

    Finally, any suggestions on best place to get a reground crank and bearing kit?
     
  12. toddslater

    toddslater SILVER Star

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    That is what I'd call good and bad news ...keeping it positive, you've done the right thing. As far as getting cranks reground...hmmm...Last year on a SBF that was in the machine shop with some serious crank issues, my machine shop "exchanged it" for @ $150. Sorry, i don't know with whom. From discussions with the machinist, I got the impression that there are outfits that specialize in regrinding of cranks and that was the cheapest and best way to go. You may need to get a crank from a cruiser bone yard. As far as bearings, I have been using Clevite 77 in a few other applications and no complaints. &nbsp:Don't know offhand if the make them for cruisers though.