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Oil Pump Rebuild - How bad is too bad? |
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PHAT69AMX 
AMC Addicted 
Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5919 |
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 Posted: Oct/20/2018 at 2:40pm |
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Can also use valve grinding compound on a piece of glass to re-surface the pump cover plate.
Compare your new Oil Pump Gear Shaft to your existing for OA Length, dia. size, and Slot Size. Deburr before sticking it up through the Cover. I've not seen AMC Oil Pump Gears with "precision machined / surfaced finished" Teeth "Tops"... Have only handled maybe 10 sets and was surprised at the lack of "finish" on the Teeth Tops...
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Oct/20/2018 at 7:57pm |
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I miss when oil pumps were made of iron and located in the oil pan where they belong. Stuff hit the fan in the 1960's. Engineers tried to make engines smaller, lighter, and cheaper. Meaning crappier. This is what happened. I've built enough AMC and Buick engines to know that I hate that oil pump design. Making the oil pump part of the timing cover, out of aluminum, and hanging it outside the engine to leak all over the place is no way to build an oil pump. Make it iron and put it in the oil pan so it doesn't make a mess if it leaks, and they always leak. |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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brownspirit
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Joined: Mar/07/2009 Location: Georgetown, MA Status: Offline Points: 1020 |
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Posted: Oct/20/2018 at 8:04pm |
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Where do they leak from, I've never seen that?
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69' BBB AMX 390/4-speed
69' s/crambler project 69’ International F210d Cummins/5+4 |
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304-dude
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Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Posted: Oct/20/2018 at 8:08pm |
The only leaks I have seen are from blow out of timing chain cover from the pressure side. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881 |
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Posted: Oct/20/2018 at 9:07pm |
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Leaks or pressure loss outside the pump are from the cover stated above, excess bearing clearance, excess lifter clearance, passage plug leaks or the oil pump bypass failure.
The oil pump itself will leak internally from high to low pressure "recirculate" though excess clearance side or gear ends. And yes the gears are not always finished well and part of blueprinting the engine is to remove any sharp edges on the top and bottom of the gears, polish, matching gear heights and measuring the TSM clearances.
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Hurst390
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Joined: Apr/20/2008 Location: secret Status: Offline Points: 5818 |
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Posted: Oct/21/2018 at 7:20am |
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The timing cover on my stock car came off a 401 that ate #6 rod bearing..I smoothed any high spots off with a stone so it spun free and set the end clearance. T carries 62-63# hot and 30 at idle on an endurance engine
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SC/Hurst Rambler
11.62 120 100% Street Legal |
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AMXrated
AMC Nut
Joined: Jul/26/2015 Location: Indiana Status: Offline Points: 290 |
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Posted: Oct/21/2018 at 10:38pm |
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Thanks for all the responses and advice. I have the new rebuild kit on order.
I measured the old gears and am getting .0025-.003 between the gear teeth and side walls. Getting about .0045 on the end clearance. Perhaps I am over-thinking this (which I have a tendency to do...) but isn't the end plate clearance spec somewhat dependent on the gasket thickness and gasket compression? I have two gaskets on hand--one from Fel-Pro and one from Sealed Power--one is measuring .009" and the other is .011". Question is, what was the factory assuming for the thickness when they created the clearance spec? Whatever gasket thickness they chose means the gears would float that much less whatever the end measurement was between the top and bottom surfaces . Because the gears stand tall and we measure from their tops to the pump housing surface, the lower end of the spec means that there is actually more distance for the gears between the top and bottom surfaces, correct? If so, then at the .006" high side of the spec, there is actually less room for the gears to move between the top and bottom surfaces. So, if I were to use my .009" gasket and assume a .0005 crush, with my current .0045 clearance there will be .003" of space for the gears to move between the top and bottom surfaces. I suppose if one were to get a .006" thick gasket in the rebuild kit and the clearance was at the top of the spec, the gears might actually bind up and not turn at all. Also, it appears that the oil pump is before the oil filter which means it is pumping the dirtiest oil first. This probably explains all the scoring inside the housing... And, I also noticed that the timing cover and pump end plate were made of aluminum, but the gears and shafts are steel. Since the thermal expansion between steel and aluminum is different, I wonder if this ever causes binding issues when clearances are too tight? I guess the moral to my story is that one should probably measure the gasket thickness when doing a rebuild and make sure that it is thicker than whatever end clearance is measured. Edited by AMXrated - Oct/21/2018 at 10:45pm |
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You can have my Hurst shifter when you pry it from my cold dead hand.
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ghinmi
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Joined: Apr/04/2010 Location: Grand Rapids MI Status: Offline Points: 978 |
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Posted: Oct/21/2018 at 11:17pm |
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That pump housing looks as close to mint as I've ever seen on a used one, set the end clearance and send it without a second though.
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1975 Cherokee S - Turbo Hemi stick shift autocross/drag race/street 9.97 @ 140.4
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White70JavelinSST
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Joined: Aug/08/2012 Location: Minnesota Status: Offline Points: 4866 |
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Posted: Oct/22/2018 at 11:39am |
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AMXrated, About that expansion thing and dissimilar metals. Steel has a lesser rate of expansion upon temperature rise than aluminum. Using that logic, the clearances between the "gears" and housing should increases slightly as the engine and oil warm up. Even the clearance between the "gears" should increase slightly as the pump housing warms up because, theoretically, the two "gear" shafts should move apart with expansion of the housing. Edited by White70JavelinSST - Oct/22/2018 at 11:42am |
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70 Javelin SST, second owner, purchased 1972
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AMXrated
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Joined: Jul/26/2015 Location: Indiana Status: Offline Points: 290 |
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Posted: Oct/22/2018 at 11:56am |
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Thanks for the response. You are probably correct. However, that also assumes the aluminum parts are expanding consistently and where we want them to. Technically the gasket could act as an insulator of sorts and cause dissimilar expansion on the end plate. My company builds aluminum plastic injection molds and occasionally we need to add steel inserts in areas of high tolerance. I have seen some very odd things happen because of the different thermal expansions.
It is probably minor in the greater scheme of things and as I said, I tend to over-analyze sometimes. I've read so much about the oiling issues (or non-issues) that AMC engines have that I began wondering if some of it may be related to the oil pump design itself.
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You can have my Hurst shifter when you pry it from my cold dead hand.
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brownspirit wrote: