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new problem losing oil pressure upper rpm's

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matty 401 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Topic: new problem losing oil pressure upper rpm's
    Posted: Oct/18/2021 at 9:57am
so cooling figured out now it is losing oil pressure at higher rpm's  drops to 0 at 6000 jumps right back up once the rpm's drop  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BDCVG Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 10:18am
Mechanical or electric gauge?
1970 AMX 390 5 spd full Control Freaks front and rear suspension
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mbwicz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 10:26am
Stock oil pan?  5 quarts or 6?  How long at high RPM before you notice it?  I'm wondering if the oil is getting trapped in the top end.  

Mike

1970 AMX, one step forward, one step back. Both steps cost time and money.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 10:57am
Spacer under the oil pickup screen?  Without it, the pickup may be sucking itself against the bottom of the pan.

Bob
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Post Options Post Options   Thanks (1) Thanks(1)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 11:57am
easiest thing to do is check the oil.  If it is full, then add a quart of oil.  One quart over full should solve the problem if it is the typical AMC oil drain back problem.  If you have a big dent in the pan, then might be too close to the pickup as tufcj says above.  I have seen pieces of valve seal clog the pickup more than once.  These are common amc v8 issues.
If you have to pull the pan, consider spending $500 on a Canton street/road race oil pan and matching pickup.  Never worry about oil supply again.  

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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 1:52pm
have an extra quart in the pan  just started doing it  never has before 6000 is where i shift  it starts about 5000 and a mechanical  gauge  and you can watch it drop  off to 0  if i let it go to 6000 
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79 concord 2 door
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68 Rogue 406
93 Cherokee 4.0 5 speed

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 2:15pm
If you hold it at 5000 (instead of shifting), the pressure remains ok?
1970 AMX, one step forward, one step back. Both steps cost time and money.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 3:39pm
Have you changed oil? It's possible that you have oil aeration at that RPM and loosing pressure.
A little light reading:
A change to a race oil may help. Don't know which brand would be best.
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matty 401 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 3:47pm
i run 20w-50 racing oil  Valvoline 
72 matador 401 the beast
79 concord 2 door
72 matador 304 grasshopper
68 Rogue 406
93 Cherokee 4.0 5 speed

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JD View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2021 at 10:53pm
Hopefully you have a faulty gauge if you rule that out you might...

Check the drain back holes in the heads under the valve covers.

Get you one of these inexpensive endoscopes.Then you can drain oil and hopefully go up into the pan and check out the bottom of pan and spacer and space between pickup and pan  like tufcj mentioned 




Edited by JD - Oct/18/2021 at 11:00pm
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