TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - Another Oil Viscosity Discussion
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Another Oil Viscosity Discussion

 Post Reply Post Reply Page  123 4>
Author
Message
Rebel Machine View Drop Down
AMC Addicted
AMC Addicted


Joined: Jul/03/2007
Location: Western Il
Status: Offline
Points: 5118
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Topic: Another Oil Viscosity Discussion
    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-


Back to Top
purple72Gremlin View Drop Down
AMC Addicted
AMC Addicted
Avatar
Charter Member

Joined: Jul/01/2007
Location: Illinois
Status: Offline
Points: 16591
Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 4:44pm
Good question.   I  wonder too
Back to Top
73hornut View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/03/2007
Location: Southern Oregon
Status: Offline
Points: 3132
Post Options Post Options   Thanks (0) Thanks(0)   Quote 73hornut Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 6:27pm
Could more be the brand of oil and where it's pressure rating is. If it is low it may not be preventing wear.
71 Javelin
74 Gremlin
79 Spirit AMX
Rogue Valley Rumblers
Like Us on FB
https://www.facebook.com/groups/1602825606650796
Back to Top
6PakBee View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar
Charter Member

Joined: Jul/01/2007
Location: North Dakota
Status: Offline
Points: 5454
Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 6:55pm
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.
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

Forum Cockroach
Back to Top
BassBoat View Drop Down
AMC Addicted
AMC Addicted


Joined: Aug/29/2008
Status: Offline
Points: 1713
Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 7:15pm
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.
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Online
Points: 6755
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 7:24pm
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.


Back to Top
Rebel Machine View Drop Down
AMC Addicted
AMC Addicted


Joined: Jul/03/2007
Location: Western Il
Status: Offline
Points: 5118
Post Options Post Options   Thanks (1) Thanks(1)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 8:43pm
Originally posted by BassBoat BassBoat wrote:

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.



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-


Back to Top
Buzzman72 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Sep/15/2009
Location: Southern IN
Status: Offline
Points: 2713
Post Options Post Options   Thanks (0) Thanks(0)   Quote Buzzman72 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 10:05pm
Originally posted by BassBoat BassBoat wrote:

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.

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.
Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Online
Points: 6755
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 10:22pm
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.
Back to Top
troutwilly View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Sep/14/2007
Location: Carriere, MS
Status: Offline
Points: 991
Post Options Post Options   Thanks (1) Thanks(1)   Quote troutwilly Quote  Post ReplyReply Direct Link To This Post Posted: Nov/27/2022 at 10:40pm
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.

Bill O.
70 AMX
Back to Top
 Post Reply Post Reply Page  123 4>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.094 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or