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Factory Oil Pump Gears, Timing Cover

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73hornut View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73hornut Quote  Post ReplyReply Direct Link To This Post Topic: Factory Oil Pump Gears, Timing Cover
    Posted: Mar/15/2019 at 4:34pm
Originally posted by ChillyB ChillyB wrote:

If anyone else considers trying to lap a housing on a vertical shed window based on my post: phone a friend to come over and kick you in the junk.   I was so far from flat that I had to undo my previous "progress".  It turns out lapping requires a gentle touch you cant achieve leaning against a vertical window pane.  Im certain most of you are laughing at my attempt.

Its flat now, having used paper taped to a granite surface plate.  But you have to go easy or you'll hog off the edges and miss the center (what happened when I tried using the window).  Adding some mass, such as a big lump of clay, would have helped even more, I think. 
Window glass is to thin and will bow with slight pressure, I recommend a 12x12 piece of 1/4in glass laid on a work surface. A piece of rubber shelf liner will keep it from moving around
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Mar/15/2019 at 1:52pm
If anyone else considers trying to lap a housing on a vertical shed window based on my post: phone a friend to come over and kick you in the junk.   I was so far from flat that I had to undo my previous "progress".  It turns out lapping requires a gentle touch you cant achieve leaning against a vertical window pane.  Im certain most of you are laughing at my attempt.

Its flat now, having used paper taped to a granite surface plate.  But you have to go easy or you'll hog off the edges and miss the center (what happened when I tried using the window).  Adding some mass, such as a big lump of clay, would have helped even more, I think. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Mar/15/2019 at 4:43am
I taped 400 wet-dry on window of my shed.  I have granite surface plate at work for a final sanding.  Checking with edge of machinist scale, it seems I'm a little high in the center.  Was probably pushing it around a little too firmly, which tends to "tip" the part you are lapping.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2019 at 7:27pm
they are flat when new.  Sand out all the scores as this is the critical area for pump pressure loss, much more so than cavity scores, which everyone focuses on.

Edit- what did you sand it on? .25 thk tempered glass is good, granite surface block is best
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Mar/14/2019 at 6:43pm
Lapped the filter housing this evening.  It had some decent scoring but it was also surprisingly not very flat aside from the scratches.  I lapped until I had 100% cleanup, but didnt go until all circular scratches were gone.  The volume loss due to remaining scratches would be insignificant compared to the overall flatness error I corrected.  Used small files to whittle away some internal burrs.  I also filed back the external casting flash since I had it in my hands with files at the ready.

Noticed something curious about the pressure bypass.  The bypass passage has a circular seat for the valve, but it appears the stem on the end is seating against the opposite wall.  So what limits the closed travel of the valve?  The circular seat, or the stem?  Could it be that the valve is held slightly off its circular seat allowing a tiny amount of flow so the oil doesnt stagnate into a solid turd behind the bypass valve?  I filled the passage ahead of the valve with water (holding my thumb over the other end), and didnt see significant leakage past the tappet but hardly a scientific test.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Mar/13/2019 at 9:12pm
If worried about the bottom scoring, you can make a piece of brass shim stock as a bearing material in the bottom.
The scoring is usually particulate in the oil as the gears will form an oil wedge.
I don't do the brass but like to help the oil wedge top and bottom by taking off the sharp edge of the gears. You will loose a minute amount of oil pressure as this creates a bypass zone, but if equal will center the gears in the housing.
Everything has it's give and take.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Mar/13/2019 at 12:08pm
Originally posted by Doug213 Doug213 wrote:

When I pulled off the pump cover both gears fell out the drive gear was NOT attached to the drive shaft. Apparently 73 wasn't ome of AMCs better tries???


This is normal- nothing holds them in but the filter adapter. Look at pictures in the TSM to understand how the system works
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: Mar/13/2019 at 11:29am
You could lap the machined face of the timing cover to shorten up the gear cavity if you end up with excessive clearance with a thin gasket.  I lapped the ratty ends of my gears so I anticipate needing to do that on mine.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Doug213 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/13/2019 at 11:20am
   According to factory specs your supposed to have .002 between the flat edge of the pump housing using a flat machinists ruler without gasket. I set mine up using plastigauge (like the utube guy) & I'm hoping .004 is going to be enough the thinest gasket I had was .007 if you add .002 clearance from the edge plus .007 for the gasket it's .009 assembled
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1982AMCConcord Quote  Post ReplyReply Direct Link To This Post Posted: Mar/13/2019 at 7:56am
Originally posted by White70JavelinSST White70JavelinSST wrote:

I couldn't get 82AMCConcords link to Planet Houston to work, so I searched for it and found this



Is this the same page you were on 82AMCConcord ?

No.. but that is a good one.. I meant to send this link... but I accidentally screwed up the link. I corrected it above now... but here it is again...

http://www.planethoustonamx.com/main/amc%20oil%20modification%20setup.htm
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