360 V8 Oil Pressure

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   Just because there is spring pressure on the pressure relief/bypass valve, does not ensure it's seated.There is a thread were John advises opening up the relief bore to 9/16" just to ensure this.
Ensure the relief plunger is seating with machinist blue or even a thin film of grease or anti seize.
Otherwise 20 PSI cold would be a sizable leak path, possibly a missing gallery plug but likely not that large.
Intake valley line is a possibility.
Doubt the bearings on a fresh rebuild could leak that much.
Oil pump clearance/scoring would likely not leak back that much oil cold either.
Your looking at approximately 4 g/m leak.

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Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Nov/13/2022 at 9:04pm
	Just because there is spring pressure on the pressure relief/bypass valve, does not ensure it's seated. There is a thread were John advises opening up the relief bore to 9/16" just to ensure this. Ensure the relief plunger is seating with machinist blue or even a thin film of grease or anti seize. Otherwise 20 PSI cold would be a sizable leak path, possibly a missing gallery plug but likely not that large. Intake valley line is a possibility. Doubt the bearings on a fresh rebuild could leak that much. Oil pump clearance/scoring would likely not leak back that much oil cold either. Your looking at approximately 4 g/m leak.

SC397 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476	Post Options Post Reply Quote SC397 Report Post Thanks(0) Quote Reply Posted: Feb/21/2023 at 12:00pm
	I finally got the time to tear this one down to see what is up with it. The first thing I did was run the oil pump with my drill to get a reading. This is a video of it. I got about 20 PSI with the drill. IMG_6455 by Rick Jones, on Flickr Then I drained the oil, pulled the pan and plastiguaged the Main and Rod bearings. The Main Bearings are King brand and plastiguaged at .0015" clearance. IMG_6488 by Rick Jones, on Flickr The Rod Bearings are King brand as well and they plastiguaged at about .0018/.0020" clearance. IMG_6486 by Rick Jones, on Flickr Time to tear it all the way down to see what else is going on.. As I was pulling the cam out I heard a "tink". Come to find out #4 cam bearing had walked out of the block. This has happened one other time in 117 engine builds (585 cam bearings). The other block was a 1973 block and this block is a 1987. I have heard this happening with a couple of other people as well with the same #4 bearing. Must be they had a issue every now and then in machining the #4 cam bearing housing. These were Dura Bond brand. IMG_6534 by Rick Jones, on Flickr So I installed a new set of Sealed Power cam bearings in with LocTite on the center 3 bearings. This is how I fixed the 1973 block and it has been on the road since the '80's. I also swapped out the King Rod Bearings for a set of Clevite brand. The Clevites run slightly tighter than the King brand. The Clevites plastiguaged more towards .0015" clearance. IMG_6516 by Rick Jones, on Flickr Time for the drill test again.. IMG_6517 by Rick Jones, on Flickr Here is a video of the engine running at idle up to temperature. IMG_6537 by Rick Jones, on Flickr Edited by SC397 - Feb/21/2023 at 12:09pm

brownspirit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Mar/07/2009 Location: Georgetown, MA Status: Offline Points: 1020	Post Options Post Reply Quote brownspirit Report Post Thanks(0) Quote Reply Posted: Feb/21/2023 at 1:52pm
	Glad to hear it is fixed, sorry you guys caught a bad break. Sounds like the issue was caught very early, and could have been a lot worse. Going forward, do you plan to use clevite cam bearings only, or a little loctite on all of them? I guess with as many as you’ve done, 2 issues doesn’t really establish a concerning pattern.
	69' BBB AMX 390/4-speed 69' s/crambler project 69’ International F210d Cummins/5+4

SC397 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476	Post Options Post Reply Quote SC397 Report Post Thanks(1) Quote Reply Posted: Feb/21/2023 at 2:16pm
	I don't plan on changing a thing. (Well except, I am still trying to retire) LOL! The 1973 engine ran over a year on the streets before I tore that one down. They both had oil pressure, just low. Even thought it turned out to be nothing that I did wrong, I am still glad that it wasn't one of those that I built and sent to Austria, England, Italy, Germany, or Sweden.