1275 Motor Overhaul from Atlanta

Discussion in 'Classic Mini' started by Minidave, Oct 21, 2020.

  1. Minidave

    Minidave Well-Known Member
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    #1 Minidave, Oct 21, 2020
    Last edited: Oct 21, 2020
    imagejpeg_0.jpg This one is on the way and expected to arrive Tuesday. The owner says it's burning oil, leaking it too, making some unhappy noises and the clutch isn't working right. He did a fantastic job crating it up, and the motor is clean as a whistle which will really make my job easier not having to clean a ton of crud off it.

    I'll tear it down and ascertain what's wrong with it, and send the block and head off to the machine shop and while I'm waiting for them I'll get the parts on the way.

    I anticipate new rings, bearings, seals, gaskets, new clutch and so on and I hope whatever is making the noises is easy to find and fix. I'm wondering if it might be bad thrust bearings. There's a stop on the end of the clutch mechanism to keep from over extending it and putting excess stress on the crank - it could be this one doesn't have it or it wasn't adjusted right allowing it to wear out the thrust bearings.

    View attachment 46115

    View attachment 46115 crate 2.jpg
     
  2. Sully

    Sully Administrator
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    Looking forward to watching this build!
     
  3. 00Mini

    00Mini Well-Known Member

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    The builds are always interesting.
     
  4. Minidave

    Minidave Well-Known Member
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    On its way to me..... crate3.jpg
     
  5. Minidave

    Minidave Well-Known Member
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    Alright, it made it......now to get it out of the box and torn down this weekend so I can get the parts sent off to the machine shop on Monday.

    IMG_20201029_100932R.jpg

    Project #2 is supposed to arrive tomorrow or Sat morning.....more on that when it gets here.
     
  6. Crashton

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    Bet you are glad that truck came with a liftgate & a pallet jack.
     
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  7. Minidave

    Minidave Well-Known Member
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    Yes, I requested it.....same driver who brought me the last engine and picked it up to go to Boston - we're on a first name basis now! :cool:
     
  8. Minidave

    Minidave Well-Known Member
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    The unboxing.....I didn't take a lot of pics - but suffice to say everything came thru perfectly - even the jug of oil - we both wondered if it would just be a big puddle when it got here, but no worries.

    IMG_20201029_114053R.jpg

    IMG_20201029_114556R.jpg

    IMG_20201029_120150R.jpg

    IMG_20201029_120348R.jpg
     
  9. Minidave

    Minidave Well-Known Member
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    Next I popped the head off......no real damage showing here - it actually looks pretty good. The head has already had hardened seats put in so we'll do a simple 3 angle valve job and replace the guides if they're worn.

    IMG_20201029_171237R.jpg

    Now the pistons, I haven't measured it but I'm betting it 40 thou over bored. The cylinders look pretty good so far, but he said he had a lot of blow by and it had started smoking like an old Chevy, leaving a trail behind him - not enough to kill mosquitoes or look like he was rolling coal, but enough that he could see it in his mirror when he drove.

    IMG_20201029_171950R.jpg

    My bet is the rings are shot - they only have 30K on them so I'm a little surprised they would wear out that quickly. The bores look fine so we may be able to do a light hone and just go back with new rings.

    Once I get it torn down completely we'll know what's up for sure.
     
  10. MCS02

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    The cylinder on the left looks like it was burning oil more than the others. Is that the case?
     
  11. Minidave

    Minidave Well-Known Member
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    Looks that way to me - he did complain that it was blowing a pretty good smoke trail and is has substantial crankcase blowby.
     
  12. Minidave

    Minidave Well-Known Member
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    #12 Minidave, Oct 30, 2020
    Last edited: Oct 30, 2020
    Once the head was off I got busy with the rest of the stripdown today.

    The front cover came off, revealing a single row timing chain with tensioner. Chain looks OK but we'll replace it as a consumable.

    IMG_20201030_122903R.jpg

    Then the back end - I noticed quite a bit of play in the pivot pin for the clutch arm and when I got the disc out the springs were loose - maybe the rattle? We'll see. He also indicated the clutch wasn't releasing correctly so we'll address the play and replace the disc. Everything inside the clutch housing was clean and dry.

    IMG_20201030_122849R.jpg

    Once I got the engine split from the gearbox I noticed that the center oil pickup tube had no screen on it? Hmmm....that's not right. I haven't found the screen or any parts of it, but there was some brass swarf around the oil pressure plunger. We'll replace those parts too, along with the oil pump, fuel pump and water pump, just for good measure.

    IMG_20201030_123934R.jpg

    IMG_20201030_124709R.jpg

    I loaded the block up on the bench and marked the rod bearing caps, then pulled them and the mains and removed the crank. Crank looks very good, records indicate it's been turned 10 thou under on both rods and mains and the rotating assembly balanced.

    The bores didn't look bad, there was no ridge at the top and I haven't yet determined if it's been bored oversize, but it looks like it might be 40 over right now based on the size of the land between the cylinders.

    Edit : turns out it's been bored only 20 over

    Once the crank came out I got a surprise......the mains and thrust washers had little wear on them, but the upper bearing in the rods were a real surprise for an engine with approx 30K use. I'll let the pictures do the explaining.

    IMG_20201030_131021R.jpg

    So, I'll mic the crank, pistons and mains and then take the crank, rods and block off to the machine shop Monday morning where we'll give them a more precise measurement and make plans accordingly. In the meantime I'll get parts ordered and hopefully everything will arrive back about the same time.
     
  13. Minidave

    Minidave Well-Known Member
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    The cam looked good but a few of the lifters were worn, I'll leave it up to Willie B if we go with a new cam or just replace the lifters. This head also has the sintered rocker arms, I'll suggest we go with the 1.13 Cooper S rockers if I can find them and of course a new rocker shaft as those are definitely a consumable.

    Here's a pic of the inside of the gearbox, the center oil pickup is the tube in the top of the pic - there should be a screen on it much like the second pic. If it got chewed up by the gears and sent thru the oil system it seems I would be finding bits of it, but maybe not.

    IMG_20201030_124709R.jpg
    IMG_20201030_124840R.jpg

    The bores looked clean with no ridge at the tops - which is usually a good indication - but the engine was blowing oil smoke and making a bit of crankcase blowby.....so I anticipated worn rings - they didn't look bad but the ring gaps on the few I checked were pretty large, a good indication of worn rings. I'll have the machine shop check for taper and wear in the bores, and if it's in tolerance we'll just give it a light hone and put some new rings in.

    We'll mic the crank carefully and see if we can figure out why the upper rod bearings are worn like this - I've never seen them wear only one of the shells like this, but it makes sense that they'll wear the tops more than the bottom shells as that's where all the thrust is taken. Mains and thrusts looked as new.

    IMG_20201030_175810R.jpg
     
  14. Crashton

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    I wonder how much farther that engine would have gone until it started having a rod knock. It is a real puzzlement about those rod bearings.
     
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  15. MCS02

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    Years ago when I rebuilt the engine on my Alfa. Shortly after finishing it it spun a rod baring. I couldn’t figure out why. I had put a lot of work into the motor. Duel Webber’s, hot cams, 10:1 pistons, and every thing was balanced. Turned out when a friend was helping me look over the parts trying to figure out what happened he removed one of the caps on the crank to look at the oil passage on the crank. He found a broke pice of a drill bit the machine shop left in the crank. Because of this the oil was not able to flow well enough.
     
  16. Crashton

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    I'm sure most everyone has a machine shop screw up story. There are a couple in my past. They taught me a couple of expensive lessons. After that I double check & then triple check everything that comes back from the machine shop. Being an old fart now the likelihood of me needing to use a machine shop is quite low.
     
  17. Minidave

    Minidave Well-Known Member
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    I'm an old fart....... :)
     
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  18. MCS02

    MCS02 Moderator
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    We are al old farts!
     
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  19. cristo

    cristo Well-Known Member

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  20. Minidave

    Minidave Well-Known Member
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    So, further info....

    I cleaned the head up and pulled the valves out - the guides look fine, valves will only need a slight touch up and they'll be good too so the head will need very little work to get it sorted. I will replace the rocker shaft and if the owner agrees replace the standard sintered rocker arms with Cooper S forged 1.13 rockers.

    On closer inspection the cam has damage on three or four lobes too, so we'll be getting another cam and a new set of lifters.

    I also found one of the pistons had a chunk of ring land broken out and being held in by the rings, so we'll be getting new piston(s) depending on whether it needs to be bored out or not.

    IMG_20201031_162429R.jpg

    Once the machine shop checks out the crank carefully, then we'll know what we're doing there too - I'll also have them check the rods for straightness - although it seems to me if the rods were bent it would wear on the cap end bearing too opposite the wear on the top bearing. So, not too sure what's going on there yet.

    There was damage to the rear cam bearing too, tho not as bad as on some engines I've seen.

    IMG_20201031_164559R.jpg

    Lastly, tomorrow I'll remove the lay shaft and take out that oil pickup tube and see if I can find the remains of the screen that's supposed to be there.
     

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