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rebuilt 390 losing oil pressure-thoughts?

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Jmerican View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jmerican Quote  Post ReplyReply Direct Link To This Post Posted: Aug/20/2019 at 5:45pm
pretty interesting 2SC. My issues have been with them too. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 390amx1 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/21/2019 at 5:57am
Unfortunately I'm not up on the correct terminology for these parts even though I've been wrenching this engine since 1978... LOL  ....  As for the comment about "filter adapter pump cover plate because a new one has the filter bypass filled in - doesn’t exist".  If this is the part that the filter screws into and then this part screws via machined surface and a gasket to the bottom of the oil pump and has the 75 psi pressure relief component (sounds like this is what we are talking about), the rebuild included a new aftermarket unit but it had a spring in and the 15/16" nut holding that spring in.  I realize that many of the aftermarket adaptors don't have the filter bypass (however, the filter bypass would not affect my situation so at the moment I'm not concerned about it)  The filter adaptor is the part that we replaced after the oil pressure issue came to a head at 16 psi.... but we couldn't get it to prime. more to come... Thinking maybe a bad gasket on the timing cover where the a loss of suction could happen from an open into the timing chain oiling area?).  Seems pretty remote but possible.  One other item is the possibility the cross over tube under the intake manifold in the lifter valley came loose.  Cant believe that as it is really hard piped but I will tear into that also before pulling the motor.  While a spun cam bearing fits the conditions at hand, I still don't believe its a spun cam bearing... I'm an Occams razor kind of guy and the cam bearing probability is just too small for me until I get more diagnostics completed.... 

Edited by 390amx1 - Aug/21/2019 at 6:45am
69 BBB 390 Tremec 5-speed AMX #13584 since 1978 (166,000 miles)
08 Zo6 Corvette
22 Ram 1500
24 CT5-V Blackwing #317
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SC397 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/21/2019 at 10:11am
If you packed the oil pump with petroleum jelly before you tried to prime it, it should have primed up. Sometimes it takes a couple of minutes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Aug/21/2019 at 1:07pm
390amx1 - have you seen the recent thread here with a situation like yours where
it seemed to maybe be caused by a missing hole in the Filter Adapter gasket ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 390amx1 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/22/2019 at 8:58am
PHAT... yes thanks.  We are putting on a filter adaptor sandwich plate tonight and will double check the gaskets...  if it primes "easily" and still 16 psi the next step will likely be removing the intake and looking at the crossover pipe.  If it doesn't prime, then removal of the front cover is likely next.  If the front cover shows no gasket issue then its on to the oil pickup....
69 BBB 390 Tremec 5-speed AMX #13584 since 1978 (166,000 miles)
08 Zo6 Corvette
22 Ram 1500
24 CT5-V Blackwing #317
Yamaha Supercharged Jet Ski's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ram Air Rick Quote  Post ReplyReply Direct Link To This Post Posted: Aug/22/2019 at 6:55pm
BTW 

I buy the Baldwin B9 filters by the case. If memory serves they are about $7 each that way.

Besides good filter media, I've read they have a great antidrainback valve.

Heard lots of good about them and they haven't failed me yet.

Rich C
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 390amx1 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/26/2019 at 6:03am
Checked the adaptor gaskets - all correct, filter adaptor sandwich plate installed, petroleum jelly used and it primed fairly easily.  Only 30 psi cold with 15w50 so when hot likely back to my 16 psi.  So now its take off the intake manifold and check crossover tube and cam bearings :(  I verified the builder used green lock tite on the cam bearings due to a spun cam bearing he had 20 years ago.  That was his only spun cam bearing in his long history of building AMC engines....
69 BBB 390 Tremec 5-speed AMX #13584 since 1978 (166,000 miles)
08 Zo6 Corvette
22 Ram 1500
24 CT5-V Blackwing #317
Yamaha Supercharged Jet Ski's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 390amx1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/03/2019 at 6:16am
An update.  Pulled the intake and saw that the crossover tube is secure.  All the cam bearings that we can see are looking to be in the correct position; however we can't see the cam bearing at the front of the engine.  With running the priming drill very little if any oil comes out the cam bearings.  We disconnected the crossover tube and then ran the priming drill and less than expected oil comes out the front crossover connection.  Also when the drill first starts we can here a "gurgle" at the front of the engine, near the front cam bearing and the 2 oil plugs.  So now its take off the front cover, check the front cam bearing, check the 2 front oil plugs and check the cover gasket.  If it weren't towards the end of driving season I would be really steaming right about now... LOL 
69 BBB 390 Tremec 5-speed AMX #13584 since 1978 (166,000 miles)
08 Zo6 Corvette
22 Ram 1500
24 CT5-V Blackwing #317
Yamaha Supercharged Jet Ski's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/03/2019 at 9:26pm
It will be interesting to hear what is discovered ?....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 390amx1 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/04/2019 at 6:26am
Wow.  The saga continues.  Front cam bearing location was good.  Both oil plugs behind cam gear intact and seated and the front cover gasket was good.  Nothing left but to pull the engine.  Has to be a malfunctioning oil pickup.  It was a new Melling one I believe.  Engine will be out this Saturday.
69 BBB 390 Tremec 5-speed AMX #13584 since 1978 (166,000 miles)
08 Zo6 Corvette
22 Ram 1500
24 CT5-V Blackwing #317
Yamaha Supercharged Jet Ski's
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