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Thread: Engine rebuild, torqued down crankshaft wonít move

  1. #1
    Join Date
    Feb 2018
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    Adelaide
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    82

    Engine rebuild, torqued down crankshaft wonít move

    Gíday all.

    Iíve started rebuilding my engine. Itís a 2.25 3 MB Petrol. Iíve replaced the big end bearings and toques down the crankshaft to 85 lb/ ft. I assumed the crankshaft should still rotate but it will not budge. Iíve not done this before hence there is probably a really basic error Iíve made. I just canít see it. I used loads of oil when seating the bearings. It rotated fine when the bearing caps were sitting on it finger tight. Iíve checked the torque wrench setting three times. Nothing seems to be snagging it. 🤷🏼*♂️🤷🏼*♂️🤷🏼*♂️.

    Any help would be appreciated

    Cheers.
    Kim

    'Maggie' 1960 Series 2 88, 2.25 Petrol 3MB

  2. #2
    Join Date
    Jan 1970
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    Canberra
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    15,704
    Did you use Plastiguage to measure journal to bearing clearance? It needs to be done.

    Issues will be wrong bearings for the diameter of journals, slightly bend crankshaft or warped block (maybe the block needs line boring)

    Garry
    REMLR 243

    2007 Range Rover Sport TDV6
    1977 FC 101
    1973 Haflinger AP700
    1971 Jaguar V12 E-Type Series 3 Roadster
    1957 Series 1 88"
    1957 Series 1 88" Station Wagon

  3. #3
    Join Date
    Feb 2018
    Location
    Adelaide
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    Cheers Garry. You may be right. I got the bearing from Turner in the UK. When i had the block hot tanked they linished the crankshaft so there maybe something in there thatís not right.
    Kim

    'Maggie' 1960 Series 2 88, 2.25 Petrol 3MB

  4. #4
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    Feb 2018
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    Adelaide
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    Iíll reverse todayís work tomorrow and check the clearances. Thanks for the reply.
    Kim

    'Maggie' 1960 Series 2 88, 2.25 Petrol 3MB

  5. #5
    Join Date
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    Canberra
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    How did you determine what bearings you needed. Normally the crank is machined to suit the available bearings - so if there is a little wear, it will be machined down to suit the next thicker bearings and will be tagged with the required size. Eg when I did my V8 all journals were fine but one had a little wear so all journals were machined 10 thou to suit 10thou oversize bearings.

    I used plastigauge to check clearances first (I did this 20 years ago as well with my 2.25 as well) and was all ok. Even so when the bearing caps were all torqued up the crank was a little tight but slowly loosened up.

    Sucking eggs time - reclean, check bearing tabs in the slots, correct sequence of cap bolts and of course correct torque. Oh - plenty of engine assembly lube.

    Garry
    REMLR 243

    2007 Range Rover Sport TDV6
    1977 FC 101
    1973 Haflinger AP700
    1971 Jaguar V12 E-Type Series 3 Roadster
    1957 Series 1 88"
    1957 Series 1 88" Station Wagon

  6. #6
    Join Date
    Aug 2006
    Location
    Melbourn(ish)
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    25,192
    do your nip and crush checks...

    also check the bearings are seated appropriately, if you put them in incorrectly so the tang press is not in its recess youve not only got the crank stuck but you've damaged the bearing.

    did you get the endfloat setup before you did up the bearing caps?
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
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  7. #7
    Join Date
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    Adelaide
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    Quote Originally Posted by Blknight.aus View Post
    do your nip and crush checks...

    also check the bearings are seated appropriately, if you put them in incorrectly so the tang press is not in its recess youve not only got the crank stuck but you've damaged the bearing.

    did you get the endfloat setup before you did up the bearing caps?
    Thanks mate. I did the end float and it seemed ok. But Iím going to reverse everything tomorrow and step through it again. I appreciate you taking the time to respond. Thank you.
    Kim

    'Maggie' 1960 Series 2 88, 2.25 Petrol 3MB

  8. #8
    Join Date
    Dec 2010
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    Mirboo North Victoria
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    Bearings

    As stated before undo all bearings one at a time check for rotation after disassembly of each bearing starting with Conrad bearings. If the Conrad bearings are not at fault and the crank wonít spin push rods up to the top of each bore after removing caps. Then start on the main bearings until the crank will rotate. Inspect each bearing to see if it is seated in the cap and rod, and each main bearing ro ensure it is correctly seated. Bearings by design are manufactured to have a crush I.e. when assembled the cap and the rod or the cylinder block will have a small gap between the mating surfaces this gap is called crush. When you assemble a bearing set first ensure the small tang/ piece sticking out on one end of the bearing is fitted to the cap/ block or rod that has a piece machined to accept the tang. If you donít and you attempt to assemble the components the bearing will clamp against the crank and cause lockup.
    When disassembling motor bearings before you order new components you should check the old components for a manufacturing number and a size if the crank was machined previously. The bearings should have the size listed on the back of the bearing 0.010Ē for example is ten thousands of an inch under standard size or 0.030Ē is thirty thousand under size. So this can allow you to first measure the journal and compare it with original measurement in the workshop manual to confirm the current size and allow you to order the correct replacement parts. On this note if the journal is still in good condition but has some slight wear say 0.0005Ē - 0.001Ē thousands of an inch do not linish the crank to clean it up. In years past I worked for a major American engine manufacturer and they conducted a very detailed investigation into engine bearing wear and they found that a crank shaft which had some wear on journals when fitted with new bearings lasted longer than the same engine with linished journals. The reason was that the crank journal had what was termed a work hardened surface and was actually smoother than a linished one. They also found that linishing a crank deposited minute abrasive partials in the porous surface of the crank. Under a microscope it was observed that the molecules of the crank when initially ground actually cut some of the molecules in half leaving minute pockets on the surface of the crank which had sharp edges and grinding stone particles in them. This was noted to be the major cause of wear during breakin, after many hundreds of thousand of kilometres/ or running hours the surface is noted to be smoother albeit slightly smaller. This surface will not damage bearings to the extent a linished crank will.

    I hope this helps in some way Gippy

  9. #9
    Join Date
    Jul 2006
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    Brisbane, Inner East.
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    10,328
    Quote Originally Posted by Kimsl70 View Post
    Thanks mate. I did the end float and it seemed ok. But Iím going to reverse everything tomorrow and step through it again. I appreciate you taking the time to respond. Thank you.
    When engine building micrometers are your friends. Measure, measure, measure. Then measure again. You should not be engine building without a full set of outside, inside, depth micrometers, dial gauge, dial test indicator. Has the main bearing tunnel been checked for truth, roundness, dimension? If it is out of whack then your machine shop needs to line bore it. You should for preference, use semi-finished main bearing shells and line bore them to tolerance to suit the crankshaft.
    URSUSMAJOR

  10. #10
    Join Date
    Feb 2018
    Location
    Adelaide
    Posts
    82
    Quote Originally Posted by Gippslander View Post
    As stated before undo all bearings one at a time check for rotation after disassembly of each bearing starting with Conrad bearings. If the Conrad bearings are not at fault and the crank wonít spin push rods up to the top of each bore after removing caps. Then start on the main bearings until the crank will rotate. Inspect each bearing to see if it is seated in the cap and rod, and each main bearing ro ensure it is correctly seated. Bearings by design are manufactured to have a crush I.e. when assembled the cap and the rod or the cylinder block will have a small gap between the mating surfaces this gap is called crush. When you assemble a bearing set first ensure the small tang/ piece sticking out on one end of the bearing is fitted to the cap/ block or rod that has a piece machined to accept the tang. If you donít and you attempt to assemble the components the bearing will clamp against the crank and cause lockup.
    When disassembling motor bearings before you order new components you should check the old components for a manufacturing number and a size if the crank was machined previously. The bearings should have the size listed on the back of the bearing 0.010Ē for example is ten thousands of an inch under standard size or 0.030Ē is thirty thousand under size. So this can allow you to first measure the journal and compare it with original measurement in the workshop manual to confirm the current size and allow you to order the correct replacement parts. On this note if the journal is still in good condition but has some slight wear say 0.0005Ē - 0.001Ē thousands of an inch do not linish the crank to clean it up. In years past I worked for a major American engine manufacturer and they conducted a very detailed investigation into engine bearing wear and they found that a crank shaft which had some wear on journals when fitted with new bearings lasted longer than the same engine with linished journals. The reason was that the crank journal had what was termed a work hardened surface and was actually smoother than a linished one. They also found that linishing a crank deposited minute abrasive partials in the porous surface of the crank. Under a microscope it was observed that the molecules of the crank when initially ground actually cut some of the molecules in half leaving minute pockets on the surface of the crank which had sharp edges and grinding stone particles in them. This was noted to be the major cause of wear during breakin, after many hundreds of thousand of kilometres/ or running hours the surface is noted to be smoother albeit slightly smaller. This surface will not damage bearings to the extent a linished crank will.

    I hope this helps in some way Gippy
    Thank you for that detailed reply. I appreciate the time and effort. When I tore the motor down I look at the specs on the bearing and attempted to order like for like. Being 3 MB engine bearings are hard to come by. I contacted Turner today as the supplied bearing had the tang on the wrong side. They suggested grinding the tab down. I think Iím going to attempt to get some new bearings and start from scratch.

    Thank you again. I really do appreciate the help.
    Kim

    'Maggie' 1960 Series 2 88, 2.25 Petrol 3MB

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