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1970 AMC 390 oil smoke from RH bank |
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PHAT69AMX 
AMC Addicted 
Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5918 |
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 Posted: Mar/24/2020 at 3:55pm |
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Sympathetic to your dilemma, hopefully something not too involved. A long shot, hope folks here aren't tired of hearing this... While the intake is off the motor, screw all the intake bolts into the heads by hand until they bottom out and measure the distance beneath the heads. Also confirm the bolts are all the same length. Measure the intake flange thickness, washers if any, etc. Do the math, confirm actual clamping action is achieved by the manifold mounting bolts before they bottom out in all the blind tapped holes... And just to point it out, anytime it is off the motor, always make sure the Intake Manifold does have in place the Sheet Metal PCV Baffle attached to the bottom of the Intake manifold with original 'Drive Screws' or other. There were 2 types, flat & domed, domed was later and on EGR type intakes. Agree that stock AMC pistons were prone to be easily detonation damaged.
Edited by PHAT69AMX - Mar/24/2020 at 4:02pm |
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pinkta
AMC Fan 
Joined: Jul/26/2014 Location: SASKATCHEWAN Status: Offline Points: 12 |
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Posted: Mar/24/2020 at 5:36pm |
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Sadly, I have no rebuild information. The lady said he had a box of papers and i would get it if she found it. I never.
Anyway, I did see a .020 on one of the pistons when i used the camera. My head is telling he that I have broken ring lands on #6 cylinder and it is upsetting the engine with excess blowby, but I really have no idea of how accurate that may be. Is there a way to test something like that?
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pinkta
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Joined: Jul/26/2014 Location: SASKATCHEWAN Status: Offline Points: 12 |
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Posted: Mar/24/2020 at 5:38pm |
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When I had the intake off there was a flat piece of metal(sort of fence like) that covered the area of the PCV on the inside of the intake. Should have taken a photo.
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Heavy 488
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Joined: Apr/27/2019 Location: In the Status: Offline Points: 3552 |
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Posted: Mar/24/2020 at 5:46pm |
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Ive had a broken ring land and it could easily be heard. Like a rattling rocker at part throttle.
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pinkta
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Joined: Jul/26/2014 Location: SASKATCHEWAN Status: Offline Points: 12 |
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Posted: Mar/24/2020 at 5:52pm |
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There is a couple of weird things at idle. I agree there is a sort of rapid light rattle if you are really listening. Also the engine seems to shudder at idle, very quick like and i cannot adjust it out with timing or carb adjustments.
Make any sense?
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Heavy 488
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Joined: Apr/27/2019 Location: In the Status: Offline Points: 3552 |
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Posted: Mar/24/2020 at 6:04pm |
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With no papers in hand, no telling if a small cam update was done during a rebuild causing the small "shudder" Unless it is opened up.
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ffltstn
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Joined: Jul/11/2008 Location: Orlando, Fl Status: Offline Points: 115 |
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Posted: Mar/24/2020 at 6:30pm |
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Years ago I have a bad oil smoke issue from my 401. I did not run a compression test, but the engine would run and rev fine. It looked good in all cylinders till I took out the #8 piston. It came out in pieces.
No issues with the bore, no sign of a problem. The fact that two cylinders have oily plugs makes me think that's not you issue, but anything is possible. |
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Ken In Orlando Fl.
'73 Javelin AMX '73 Javelin |
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Sonic Silver
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Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7950 |
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Posted: Mar/24/2020 at 6:55pm |
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pinkta
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Joined: Jul/26/2014 Location: SASKATCHEWAN Status: Offline Points: 12 |
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Posted: Mar/24/2020 at 7:24pm |
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On the matter of a cam issue and the small shudder at idle. The car came with a brand new cam and lifters. No idea why? Could this be someone(now deceased) knew what was going on? can a cam issue cause this smoking on one side?
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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6876 |
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Posted: Mar/24/2020 at 7:52pm |
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The cam will not cause oil into a cylinder. As for the baffle, either flat or dome will be fine as long as you use one on the stock manifold. It was common practice to have steel mesh in the baffle to slow flow and allow oil a path to collect to the bottom of the baffle. That may have even been factory.
Some have put scotch brite pads in here - lots of debate on that one (I would not)! Take Ken's and Phat's advisement's first and if no problem is found, time to pull the right head to have a good look. Another possibility that I would not wish on anyone, is that the person that did the rebuild did not use the AMC torque sequence. This can cause the block to crack from the intake side of the block to the cylinder - especially if it has been over bored. When taking the head bolts out, if one on the intake side of #6 is wet with oil, mag flux the cylinder.
Edited by Trader - Mar/24/2020 at 7:54pm |
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PHAT69AMX wrote: