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rebuilt 390 losing oil pressure-thoughts? |
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Jmerican
AMC Addicted Joined: Mar/29/2016 Location: Seattle, Wa Status: Offline Points: 585 |
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pretty interesting 2SC. My issues have been with them too.
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390amx1
Supporter of TheAMCForum Joined: Jul/22/2011 Location: Medina, OH Status: Offline Points: 524 |
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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 |
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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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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5428 |
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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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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5905 |
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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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390amx1
Supporter of TheAMCForum Joined: Jul/22/2011 Location: Medina, OH Status: Offline Points: 524 |
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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....
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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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Ram Air Rick
Supporter of TheAMCForum Joined: Jul/04/2007 Location: United States Status: Offline Points: 2667 |
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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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390amx1
Supporter of TheAMCForum Joined: Jul/22/2011 Location: Medina, OH Status: Offline Points: 524 |
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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....
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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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390amx1
Supporter of TheAMCForum Joined: Jul/22/2011 Location: Medina, OH Status: Offline Points: 524 |
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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
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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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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5905 |
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It will be interesting to hear what is discovered ?....
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390amx1
Supporter of TheAMCForum Joined: Jul/22/2011 Location: Medina, OH Status: Offline Points: 524 |
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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.
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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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