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Another Oil Viscosity Discussion |
Post Reply | Page 123 4> |
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5118 |
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Posted: Nov/27/2022 at 4:25pm |
Having a case of Deja-vu. Was looking through old photos of the first 401 I had in my AMX that had bearing problems back in 2011. That engine was originally in my Gremlin and performed well for several years. Shortly after I put it in the AMX it developed low pressure. After I took it home and disassembled it mains 2 & 4 were worn to the copper and the #2 crank journal has some copper embedded in it, the exact same wear my current 401 has even they are two separate engines. In both cases I ran 10W30. Now I'm wondering if that's too thick for standard AMC bearing clearances. Read an article on Enginebuildermag.com that said modern engines like the Chevy LS and Ford mod V8 engines have clearances of 0.0015"-0.0020" (nearly the same as the AMC) and use 5W20. Would 5W20 be a better choice for an AMC V8 with standard bearing clearances? -Steve- |
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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Good question. I wonder too
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73hornut
AMC Addicted Joined: Jul/03/2007 Location: Southern Oregon Status: Offline Points: 3132 |
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Could more be the brand of oil and where it's pressure rating is. If it is low it may not be preventing wear.
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71 Javelin
74 Gremlin 79 Spirit AMX Rogue Valley Rumblers Like Us on FB https://www.facebook.com/groups/1602825606650796 |
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5454 |
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I'm just spitballing here but I would think that the lowest viscosity multiweight that gives you an acceptable hot idle pressure would be acceptable.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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BassBoat
AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1713 |
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been common knowledge for at least 55 years of my life that oil viscosity needs to be matched to bearing clearance. Most likely the problem is you ran oil that was too LOW viscosity. JFGI. also been common knowledge for the last 20 years at least that oil additives that worked for old cars with parts under heavy load were removed to improve catalytic converter life, and that only oil with HIGH viscosity is still allowed to have reasonable levels of these additives, theory being that old cars that benefit from high viscosity don't typically have catalytic converters. Just my theory, but you probably did damage to rocker arm and lifters that contributed to crankshaft bearing wear. I decided to JFGI for you. This article addresses the issue. https://www.enginelabs.com/news/what-i-learned-today-bearing-clearances-vs-oil-viscosities/
Also note that great big fat journals for fantastic old school V8s need big fat oil clearances so you can not simply tighten up oil clearance and run stupid thin oil. Further note that bearing engineers are not suggesting 0W20 for your daily and your wife's car, that comes from someone trying to improve their CAFE.
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Online Points: 6755 |
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PO, most of us don't have the same stock engine of the 1970's and therein can be the problem.
We add compression, flow, and upgrades that make these non OEM engines. We typically drive them harder also. Not just the track, but longer idle times in traffic and longer/higher sustained RPM's on the highways also. If you drive a performance vehicle, then it likely needs a performance motor oil. For the conditions near me and driving habits, I liken the engine to needing not a race oil, but a stronger performance oil. API does not provide specifics on performance oils while ACEA does. For this reason I use a 5W40 in my 401 and have no issues with it. I'll provide 2 guides I use: API seems to change oil specifications faster then the wife changes her mind. But the API SN or SN+ never reflect this. Got really miffed when Quaker State highly rated 5W30 from oil testing went from a HTHS A3/B4 to a A1/B1 but only the fine print on the jug reflected this. I use the BMW LL-01. It does not matter the brand, that LL-01 is a minimum BMW specification that does not change. |
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5118 |
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That article seems to support a thinner oil with the tight AMC factory clearances (mains 1-4 are 0.001"-0.002", main 5 is 0.002"-0.003"). I've been looking at 5W30 Quaker State “Full Synthetic”. The 540 Rat oil blog says it tested best for PSI value along with enough additives to use with a flat tappet cam. You can read it here: https://540ratblog.wordpress.com/ Look for "The “WEAR PROTECTION RANKING LIST itself, begins here:" heading. -Steve- |
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Buzzman72
AMC Addicted Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2713 |
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I just googled JFGI, and it came back as the Jewish Federation of Greater Indianapolis. I have no idea what that means in the context of engine oil.
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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Online Points: 6755 |
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That article seems to support a thinner oil with the tight AMC factory clearances (mains 1-4 are 0.001"-0.002", main 5 is 0.002"-0.003"). I've been looking at 5W30 Quaker State “Full Synthetic”. The 540 Rat oil blog says it tested best for PSI value along with enough additives to use with a flat tappet cam. You can read it here: https://540ratblog.wordpress.com/ Look for "The “WEAR PROTECTION RANKING LIST itself, begins here:" heading. This is exactly the point and I was using that oil. When that test was done, that oil had an ACEA HTHS rating of A3/B4, then it was switched to A1/B1. Sacrifice wear protection for fuel economy and emissions. Like to see results of a retest! You have to read the container now to determine the wear protection. The API Sx means absolutely nothing except it's newer and not necessarily better! Read the newest ISLAC: The proposed ILSAC GF-6B will provide the same performance as GF-6A, but with the added aim of lower HTHS to deliver potential further fuel economy benefits.
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troutwilly
AMC Addicted Joined: Sep/14/2007 Location: Carriere, MS Status: Offline Points: 991 |
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I'm gonna guess JFGI means Just Frickin Googled It. Now, as for oils, I have no input other than I use Valvoline VR-1 20W-50 for its zinc content (not looking for another discussion on that). I would try a lighter weight but can't find it anywhere. I will also say I've never checked my engine for bearing wear. |
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Bill O.
70 AMX |
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