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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 Posted: Aug/25/2022 at 1:56pm
Originally posted by 79 SPirit 79 SPirit wrote:

That pressure is good at hot idle.  You might try for 60psi at 6000.  You can shim the relief spring to get a few more psi. I’m shifting at 5500 with cast pistons and 55psi and rev limiter set at 5800
what does it take to shim the relief spring i believe the one in there is still original  to the motor 
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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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Aug/25/2022 at 2:19pm
If changing grades, try a 10W40 race oil next. This should provide a little more top end RPM pressure and the same low RPM pressure.
Don't know why, but seen more break a rod using 20W50 at the end of a track run or on deceleration after tire warm up, then using any other lighter weight oil.
Just PO, heavy weight oil and hard deceleration seems to be a rods week point.

The ultimate in oil bypass spring adjustment:


Edited by Trader - Aug/25/2022 at 2:28pm
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79 SPirit View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 79 SPirit Quote  Post ReplyReply Direct Link To This Post Posted: Aug/25/2022 at 2:27pm
If you have an old relief spring probably just replace it with the red spring might just do it. Small washers can be used for shims to adjust pressure
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Regamble1969 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Regamble1969 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/25/2022 at 8:47pm
This strikes me as a pump cavitation problem. Gear type pumps and front mounted pumps both suffer from this more than in-pan style pumps or gerotor pumps. Lots of factors in a cavitation problem, but there is a fantastic article here that might help. There are a lot of passages our AMC oil travels through, and the remotely located pickup can make it problematic.

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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: Aug/20/2023 at 5:49pm
motor pulled freshen up  rings all new bearings new pick up and pan  turns 6000 at 80 pounds of oil pressure and holds when going into second   I am happy 
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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