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Hot Rods sbf main bearing

Discussion in 'The Hokey Ass Message Board' started by stegman, Oct 2, 2019.

  1. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    i have a sbf with about 2k miles on it after a complete rebuild with a failed number 1 main in my 32 roadster. i noticed it by low oil pressure at about 15-20psi at hot idle (normal was 40). also had a front main seal leaking pretty bad. i pulled the pan right away and started pulling main and rod caps. really the number main was the only one that looked like it failed, no spun and grooves in crank or cap, it polished it out pretty easy. question to all the deep knowledge on the HAMB, do u guys think just replacing the main bearings and a clean up in the car would be good? Not looking to get 50k miles out of it, just don’t feel like a complete rebuild anytime soon. pic on the way. thx IMG_0795.JPG IMG_0796.JPG IMG_0793.JPG IMG_0794.JPG IMG_0797.JPG


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  2. ididntdoit1960
    Joined: Dec 13, 2011
    Posts: 897

    ididntdoit1960
    Member
    from Western MA

    how tight was the fan belt?
     
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  3. 63Compact
    Joined: Feb 14, 2007
    Posts: 1,178

    63Compact
    Member

    I know its no help but that's the funniest reply I've seen here in a while.
     
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  4. RmK57
    Joined: Dec 31, 2008
    Posts: 1,162

    RmK57
    Member

    Wouldnt you want to find out why it spun bearings with only 2000 miles on it?
     
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  5. oldiron 440
    Joined: Dec 12, 2018
    Posts: 1,172

    oldiron 440
    Member

    That one must get some abuse because it seams like every core I take apart its that main that looks rough.
     
    Last edited: Oct 2, 2019
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  6. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Sorry bad written thread, wrote on my iphone in garage. Actually the fan belt was pretty tight. i pulled a couple of rod bearings and they looked good, normal wear i believe. I may just roll new mains in, install a new oil pump and change the oil and filter a couple of times. The debris looked like it was from number 1 main, but going to change em all. Also should i just bench prime the pump, giving the rest of the motor should be primed? Thx all and wish it luck! Any thoughts and why the front main failed?..


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  7. I would be looking awful hard at why this happened. Is the oil supply restricted to this main? Were the bearing clearances checked upon installation? Sadly, all that bearing material that came off of that failed bearing went right through the 1 and 2 rod bearings. This might be a dumb question, but was the grooved bearing installed in the block? My first thought on the failure is lack of lubrication.


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  8. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,117

    Relic Stew
    Member
    from Wisconsin

    Make sure the oil gallery is clear and the bearing slot is aligned with the hole in the block.
    Sometimes a bearing with the wrong over/undersize will get mixed into a box, so always check clearances.

    Ford changed the firing order on the 351W and 5.0 HO to reduce loads on the #1 main bearing, so there is something to this. This shifts the sequential firing from the front bearing to the rear bearing. GM also changed to this order on the LS engine series. A 351W cam can be installed in a 289/302 to change the firing order.
     
    Last edited: Oct 2, 2019
  9. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Yes groove up. After i noticed the low idle oil pressure i changed the oil and filter where i found the debris. Ran and drove it a couple of times and drained it again and the oil and filter looked pretty clean. I hear ya, where did the junk go, everything after number one appeared pretty good. Its a new std crank too.


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  10. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Also the car sat for awhile, wonder if the pump got dry?


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  11. RmK57
    Joined: Dec 31, 2008
    Posts: 1,162

    RmK57
    Member

    Might be a balance issue. Wrong balancer, flexplate......
     
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  12. My opinion is to disassemble the engine. Check the main bores for size and alignment. There is something wrong for that to occur. You can reuse the piston rings and all the bearings that look good. I know it's more work but the price will be much higher when it does it again. Without knowing the reason, it will do it again.
     
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  13. I thought lack of lubrication ,,,,since the top Babbitt layer is gone.
    Mis sized journal,,,,mis sized bearing.
    I thought about the timing chain being way to tight,,,,but that should mostly affect the top shell.
    Can you apply air to the oil journals and see if they are clear ?
    Could have just been a bearing that was too tight?
    Does the main journal still look good?

    Since both shells have uniform wear,,,I suspect a clearance issue,,,just a guess.

    Tommy
     
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  14. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Yep on the pull, clean and check! The motor was balanced with the balancer and flywheel. Just was hoping that a old school quick repair would get me by. I may repair and keep a eye on the oil, filter and pull the pan again in a couple of months and pull a cap, easy pan removal and install. thx guys......


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  15. I’m interested in this, as I’m going to un-assemble a “never been run” 302. I simply have no history on it and I feel mine lacks assembly lube and has other non-perfectionist looking details. Please update this thread if you find any other issues. I’m looking for about 4 stamped steel stock rocker arms too, if anybody has some laying around...
     
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  16. seb fontana
    Joined: Sep 1, 2005
    Posts: 5,991

    seb fontana
    Member
    from ct

    He said the bearing didn't spin..Crank looks good , I would bet wrong size bearing..I would do new bearing for #1; check clearence on all..
     
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  17. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Yep new bearing and keep my eye on it. Oil, filter and pan pull after a couple of oil changes. I’ll keep informed


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  18. deathrowdave
    Joined: May 27, 2014
    Posts: 1,960

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    Oil flow....pump is a positive displacement pump, meaning that if it turns, it pumps. Oil flows from the pump to the filter. Out of the filter and to the main galley. Down the main galley. Along the main galley there are passages drilled down to the main bearings. In the main saddles there are small holes, one in each saddle. Those feed the cam bearings. Oil flows from the main feed holes to the saddles and into the cam bearings via a slotted main bearing. At the back of the block, you will find a core plug (freeze plug) under the intake. One hole goes nearly straight down. The other is drilled at an angle. The one that goes straight down--it intersects all the way down to the main galley. Both of these holes intersect the lifter galleys. Lifters are oiled through these galleys and of course the springs and rockers are oiled through the pushrods.
     
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  19. deathrowdave
    Joined: May 27, 2014
    Posts: 1,960

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    Many years ago , I found out the hard way that a tight engine will force the galley plugs out behind the chain and top timing gear . This spells disaster on oil pressure and bearing lube .
     
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  20. Dyce
    Joined: Sep 12, 2006
    Posts: 1,817

    Dyce
    Member

    I would at least check the cam bearings. Some timing chains are to tight and can break the oil film at startup. If that is the case the front main bearing will be a bitch to get in.
     
  21. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,410

    sunbeam
    Member

    Does the front rod bearing look good It gets it's oil from that main. And I would look hard for a broken crank was there any noise in the motor? The front main is the first thing to get oil from the pump.https://images.search.yahoo.com/search/images?p=302+ford+oil+passage+diagram&fr=yfp-t&imgurl=http://www.supermotors.net/getfile/172859/original/smallblockoiling.jpg#id=15&iurl=https://www.ford-trucks.com/forums/picture.php?albumid=42281&pictureid=149229&action=click I did tear down a 283 chevy that looked a lot like this low oil pressure and bad front main. It was a cast crank motor when I took the crank out was in two pieces. It broke between the front main and the first throw. The guy claimed it never made noise just low oil pressure .
     
    Last edited: Oct 3, 2019
  22. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,786

    Ebbsspeed
    ALLIANCE MEMBER

    Is there an oversize marking on the outside of the bearing shell? .010 oversize bearing shown, for crank that's ground .010 undersize. One of these on a standard crank would certainly be an issue, but the motor might not even turn over if an oversize bearing was clamping down on a standard size main journal.

    Bearing.JPG
     
    Last edited: Oct 2, 2019
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  23. Charlietruck62
    Joined: Apr 2, 2019
    Posts: 29

    Charlietruck62

     
  24. Cam bearing possibly turned blocking oil hole.
     
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  25. Sunbeam states the #1 rod gets oil from the main journal.
    If it is good,,,then the main would have to be receiving oil from the galley.

    Sounds more like it is just a bad bearing,,,or mis sized bearing.
    Keep us informed.

    Tommy
     
  26. HotRod33
    Joined: Oct 5, 2008
    Posts: 2,253

    HotRod33
    Member
    from MO

    If your going to change the oil pump put a high volume pump in it... I have done that on all the sbf engines I run...
     
  27. RmK57
    Joined: Dec 31, 2008
    Posts: 1,162

    RmK57
    Member

    I would think if it were the wrong bearing you would need a breaker bar to turn the engine if the machining was done correctly.
     
  28. Not necessarily,,,,not if it is mis sized and is not correct for the clearance.

    And it could just be a bad layer of Babbitt coating on the surface and it came off,,causing excessive clearance then.

    It does seem to be uniform in its appearance.

    Tommy
     
  29. stegman
    Joined: Aug 12, 2008
    Posts: 32

    stegman
    Member

    Thx all great insight, bearings are std and crank is new std. Ran great, no misfire, great idle ect. Yes on the high volume and yes number 1 rod bearing and journal looked good. Going to blow out oil passage with clean oil and also plastic gauge number 1 main. Thx.......


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  30. It must have been a bad bearing,,,,,I thought the crank and journals looked new!
    If the coating came off the bearing,,,that might explain your front seal leakage?
    Those rods look good too.
    Looks like a really good engine!

    Tommy
     

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