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Factory Oil Pump Gears, Timing Cover |
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73hornut
AMC Addicted Joined: Jul/03/2007 Location: Southern Oregon Status: Offline Points: 3132 |
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Posted: Mar/15/2019 at 4:34pm |
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71 Javelin
74 Gremlin 79 Spirit AMX Rogue Valley Rumblers Like Us on FB https://www.facebook.com/groups/1602825606650796 |
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ChillyB
AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371 |
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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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ChillyB
AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371 |
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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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Steve_P
AMC Addicted Charter Member Joined: Jun/28/2007 Status: Offline Points: 3759 |
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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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ChillyB
AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371 |
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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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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6755 |
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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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Steve_P
AMC Addicted Charter Member Joined: Jun/28/2007 Status: Offline Points: 3759 |
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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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ChillyB
AMC Nut Joined: Nov/14/2018 Location: PA Status: Offline Points: 371 |
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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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Doug213
AMC Fan Joined: Mar/09/2019 Location: Grand Jinction. Status: Offline Points: 2 |
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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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1982AMCConcord
AMC Addicted Joined: Jul/13/2012 Location: Kenosha, WI Status: Offline Points: 1286 |
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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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