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Oil Pump Rebuild - How bad is too bad? |
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AMXrated 
AMC Nut 
Joined: Jul/26/2015 Location: Indiana Status: Offline Points: 290 |
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 Topic: Oil Pump Rebuild - How bad is too bad?Posted: Oct/19/2018 at 10:41am |
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So, I took the oil pump apart on my 360 rebuild. I anticipated needing to buy a rebuild kit--what I did not anticipate was the amount of scoring inside the housing.
Question is--how much is too much? I've got the Figure 8 syndrome on both the top and bottom surfaces and some severe gouging on the side walls. Apparently the previous owner was using a sand additive... I can set the bottom plate up on a mill easily enough and dust it, but the inside surface would be a tough set-up. Not sure how good of a flatness spec I can hold with emery cloth... Factory spec is .0005-.0025" for impeller to side wall clearance and .002-.006" for impeller to filter end plate clearance. Not sure how much clearance I have now and it really doesn't matter since the old gears are trash. Obviously I need to order the rebuild kit first to see where the new impellers measure out, but how far out of spec can I be before I need to start looking at a new timing cover? Thanks.   |
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You can have my Hurst shifter when you pry it from my cold dead hand.
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304-dude
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Posted: Oct/19/2018 at 11:22am |
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You can read surface by hand using sandpaper on a flat surface in swirling sweeps, or have a machinist.
Or just buy a bulltear pump plate. It's stainless and sandwiches between the adapter to seal. It uses the rebuild kit gasket and comes with an extra for mounting the plate to the cover. Though I noticed you need to order a cover from bulltear as well, that one is toast. |
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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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target
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Posted: Oct/19/2018 at 12:09pm |
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Doesn't look that bad to me. If oil pressure was good when you took it off it will be good when you put it back. All have some scoring.
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6PakBee
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Posted: Oct/19/2018 at 1:23pm |
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Where did you get that side clearance specification? I just looked in the '68 TSM (it was handy) and it lists 0.002 - 0.004" for the gear to housing clearance. I wouldn't overreact until I got new gears. With the new gears if you are on the lower side of the clearance range I wouldn't worry about it. If you are near the maximum, or over, then I would be concerned.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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bcsideshow
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Posted: Oct/19/2018 at 7:38pm |
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I had the same questions. I listened to the forum experts and They were right. You could research some old posts but the consensus seems to be the pump cavity scores are less of a concern. The end plate and clearance is critical. I just put two together that looked like that with no pressure issues after together.. The end is more critical. I put some fine sand paper on a surface plate and got all of the grooves out of the end plate then reassembled. Good pressure cold and hot. Hard to truly judge the cavity scores from pictures but mine looked similar.
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1969 SCRambler "B"
1970 AMX 390 Auto 1968 AMX 390 Auto 1970 Rebel Machine Project 1969 AMX 390 4SPD Project 1969 AMX 390 Auto Project 1969 Javelin 390 project 1997 Cherokee lifted 1998 TJ Lifted |
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AMXrated
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Posted: Oct/19/2018 at 10:56pm |
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Got the clearances from a 73 TSM. I agree--going to order a the Melling rebuild kit from Summit and see what the new impellers measure out to. Hopefully the tolerances will stack up in my favor.  |
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You can have my Hurst shifter when you pry it from my cold dead hand.
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FSJunkie
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Posted: Oct/20/2018 at 3:26am |
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I doubt you'll get within spec on the gear to body clearance with that timing cover. Gear end clearance is easy to adjust. Use thicker gaskets, stack gaskets, or shims to increase clearance. Lap the gasket surface of the timing cover to reduce clearance. The gear to body clearance is the hard one to correct. There is no such thing as oversize gears. Even a new Bulltear timing cover with new Melling gears ends up around .002" gear to body clearance. They probably don't make them tighter because of manufacturing tolerances and distortion. Follow the factory published specifications. This is AMC, not GM. The published specs are actually correct and work well. You can trust them here at AMC. Make sure the gears turn freely after the pump cover is installed and torqued to spec. The housing distorts as the bolts are torqued and sometimes that is enough to make a pump that turned freely with clearance before to now jam up after the bolts are torqued. It's also why following proper torque is important. It would be nice if the oil pump gear pocket was machined out of the timing cover with a torque plate installed, but I'm pretty sure it isn't. Your perfect clearances with the cover off turn into imperfect clearances with it on. I hate that. I learned everything I know about AMC oil pumps from building Buicks. They're like the AMC oil pump but ten times worse. |
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Trader
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Posted: Oct/20/2018 at 7:25am |
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A figure 8 (more like oval with 2 holes) shim can be made for the top also. But it means machining out the full area flat and depending on your resources, a new timing cover may be cheaper.
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6PakBee
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Posted: Oct/20/2018 at 8:15am |
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I looked in a '72 TSM and it had the exact figures you posted. I then looked in my parts book and it appears that from 1967 up, the gears and the cover all have the same part numbers. So the question arises, how did the clearance magically decrease over the years with the same components? Obviously something had to change, cover, gears, both?????
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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401MATCOUPE
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Posted: Oct/20/2018 at 11:23am |
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If you are running a stock engine and RPM range I would not be concerned, I have seen much worse make 40 lbs oil pressure with 10W30 cold at 1500 RPM. There are places to tighten up the overall losses in the engine, easiest is the extra slots in most cam timing gears.....
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Ross K. Peterson
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6PakBee wrote: