Looking for the threads regarding rear gallery oiling

Discussion in 'Big Block Cadillacs' started by Cadillac Kid 1, Nov 8, 2018.

  1. Cad Man

    Cad Man Active Member

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    I would like to know how the main bearing eccentricity from a chebby size journal compares to that of a 3.25 Caddy ?

    One thing I do know and have verified is the 2.5 Cad rod bearing does not have nearly the same increase in gap
     
  2. Red98422

    Red98422 Active Member SUPPORTING MEMBER

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    Gave who away? I’m just some guy who’s been reaseaching the forums on my favorite engines.

    Not in any way trying to pretend or otherwise imply that I’m any other member here.
     
  3. dave brode

    dave brode Well-Known Member

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    Greg,
    None of the fittings that I used were inverted flare. The silver fittings use two piece flare nuts, just like nosgood's, except they are cad plated steel and 1/3 - 1/2 the price. The elbows are male to female flare.

    I would pay very close attention to what Cadman says on brg clearance. I, like most guys, used the old .001" per inch of journal. Imo, it works ok until a certain power level is reached. Above a certain level [say mid 600s?], bearing issues arise.

    https://cadillacmagazine.com/forums/threads/if-i-was-building-a-caddy-engine-today.18415/

    Dave
     
  4. Cadillac Kid 1

    Cadillac Kid 1 Active Member

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    Thank you Dave. I misspoked’d about the fittings. I can see they are male/female 6 AN and I can see why you used them.
    Greg Surfas
     
  5. Cad Man

    Cad Man Active Member

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    Last edited: Nov 23, 2018
  6. Cad Man

    Cad Man Active Member

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    Too much either way is no good of course..I would rather have less

    The bearing is engineered to have a specific clearence to maintain the hydrodynamic wedge and has eccentricity designed into it to account for distortions at power and rpm..
    More clearance requires more pressure and volume ..no increase in either over stock guarantees disaster imo

    http://www.substech.com/dokuwiki/doku.php?id=geometrical_parameters_of_engine_bearings

    [paste:font size="3"]|lubrication parameters.

    Higher oil clearance causes an increase of the oil flow passing through the bearing and resulting in a lower oil temperature rise. However higher clearance produces less uniform distribution of the oil pressure - greater pick pressure, which increases the probability of the bearing material fatigue. Minimum oil film thickness decreases at higher pressure and may cause direct metal-to-metal contact between the mating surfaces. Too high clearance produces excessive vibration and noise. Lower oil clearance results in a more uniform oil film pressure distribution and a greater oil film thickness however too small clearance causes overheating the oil and a sharp drop of its viscosity. High performance bearings has an increased clearance providing more stable hydrodynamic lubrication under conditions of high loads and high rotation speeds.
     
    Last edited: Nov 23, 2018
  7. Cad Man

    Cad Man Active Member

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    [paste:font size="3"][​IMG]
    The difference between the maximal and minimal wall thickness is called eccentricity:

    eccentricity = T - Te

    Eccentricity produced by the varying wall thickness is added to the eccentricity “e” caused by the displacement of the journal from the concentric position. Such increased total eccentricity allows to establish a more stable regime of hydrodynamic lubrication.

    With regards to the hydrodynamic conditions the bearing with an eccentricity is equivalent to the bearing with an increased diameter (or increased oil clearance). The oil wedge of the bearing with eccentricity is the same as the wedge formed by the bearing with an increased diameter (”effective bearing diameter”). On the other hand the actual bearing diameter is not changed, thus the adverse effect of the bearing clearance on the vibration and noise is prevented.

    Bearing eccentricity is designed to compensate distortions of the bearing housing bores caused by the forced applied to the connecting rod and to the crankcase. Under the forces the housing bore is stretched in the vertical direction. As a result the bearing diameter measured along the parting line decreases (close-in) changing the shape of the oil wedge. The bearing eccentricity allows to retain the wedge shape of the oil gap, which is required for hydrodynamic regime of lubrication. High performance engine bearings operating at high rotation speed and high loads have an increased amount of eccentricity.

    Advanced quality control of machining operations allows to produce bearings with tight tolerance. Such tight tolerances result in superior consistency of the oil clearance and eccentricity.

    Recommended values of eccentricity:

    For passenger cars: 0.0002 - 0.0008” For high performance cars: 0.0006 - 0.0012”

    Location of the eccentric wall measurement (h) is within the range 1/4-5/8” depending on the journal diameter. h=3/8” for 1.6-3.4” journals.

     
    Last edited: Nov 23, 2018
  8. El Diablo

    El Diablo Active Member

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    Cad Man, you mentioned the use of hi performance bearings requiring more clearance. Are you referring to a harder bearing material or softer? Or just a narrower riding surface?
     
  9. 48Austin

    48Austin Active Member

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    Didn't say that! Just know who the "Mad Cadder" is now. Why the change , I don't know. Good info from this guy!
     
  10. gary kosier

    gary kosier Active Member

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    Interesting. Many years ago, I remember reading in one of the circle track magazines about some guys
    who were running 427 cu.in. Fords and having trouble with rod bearings at high RPM. They decided
    the big end of the rod was stretching vertically and wiping the sides of the bearings. So they honed the
    big ends of the rods with a C-clamp across the parting line. This made the static size of the big end
    slightly wider than it was tall. Claimed it fixed the problem. 'd forgotten about that story until now.

    Gary Kosier
     
    Darius likes this.
  11. Cad Man

    Cad Man Active Member

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  12. Cad Man

    Cad Man Active Member

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    According to the chart load capacity is greatest at .0019 but look what happens to the amount of flow ( and of course pressure loss in the bearings ) between .002 and .0035 !!

    And then what's left for the rod bearings ?. After the oil finds it's way thru the crank and "G" forces
     
    Last edited: Dec 4, 2018 at 10:00 AM
  13. Darius

    Darius Well-Known Member SUPPORTING MEMBER

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    Great Stuff!

    Glad I went "tighter" on my clearances.

    Thanks,

    bro. d
     

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