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Mandatory oil system mods

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Rebel Machine View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 7:24am
The oiling passage in all the aftermarket cams and timing gears needs to be checked. The front cam journal supplies a path for oil going to the distributor drive gear. Many times the timing gear has that groove in the wrong place or the groove extends beyond the diameter of the cam's front journal.

This is a comparison of an aftermarket cam gear (left) and an original AMC gear (right). You can see the aftermarket gear groove extends well beyond the distance of the original gear.


The arrow shows the timing gear groove extending past the cam journal diameter causing a loss in flow going forward to the distributor drive gear.


I've welded and machined the timing gear to fix that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scotty54 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 8:39am
This is the first I have heard of the extra quart. Any issues with the depth of the stock pan and frothing? Do the compacts have a different pan that may preclude the extra quart?

I have always done the oiling mods originally recommended by Performance American Style and never had a bearing fail. But it appears that those who don't do the mods haven't had a fail either.

Great info in this thread!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 9:07am
The extra quart was a thought up patch early on as people thought the problem with the AMC motor was too much oil being pumped to the top of the cylinder heads and that caused the oil pick-up to catch air.
Modern thinking and track proven is oil aeration being the big problem, oil frothing in the crankcase and picking up air. The extra quart would actually aerate the oil more as the crankshaft spins through the excess oil.
This air/oil mix would then be pumped through the engine and not lubricate near as well as straight oil. Air separation in the top of the engine can cause even more problems if not achieved in the valley or rockers.
An extra quart oil pan reduces aeration of the oil and also provides for "spirited" driving as oil is pushed front to back or side to side.
The stock pan with stock oil level is good for every day driving. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 1:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobsterfl Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 2:03pm
Lots of good advice in all these posts.

I am old enough to remember AMC being involved in the Trans Am racing series, and have read numerous articles over the years describing blown-up engines due to oiling problems. Of course, these cars were revving high and experiencing really high g-forces in hard cornering.  The final ultimate fix was to change over to a dry sump, belt driven external pump with a large external oil tank, very similar to what NASCAR uses today. That would be overkill for most of us. 
Bobsterfl
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2019 at 2:14pm
The crank is in the oil at start up and an extra quart exaggerates the issue.
 
Oil return is marginal in an AMC because of small return openings in the heads
and the collection of oil in hard acceleration in the lifter gallery area.
 
Stock umbrella seals broke up and the debris blocked the returns and cause
general mayhem in the oil system.
 
Yes, I have seen a number of AMC V8s that had oil pressure
only until the oil was all pumped to the valve covers.
 
Sludge and umbrella seal debris slowed the return.
Wait a few minutes and re-start and oil pressure was back.
For a few seconds.....
 
The plastic button on the oil pick-up had a similar effect.
The button becomes dislodged and the pick up goes flat
against the bottom of the pan.
 
AMC V8 is a great motor when all is well, any motor fails with no lubricant.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/28/2019 at 6:36am
I don't have the supporting documentation any more, and can't remember where I even got it, but the AMC Gen2/3 V-8 was designed for six quarts from the start. Six quarts are specified for police and heavy duty fleet use (taxis and such) -- and they use the SAME OIL PAN STAMPING. The police pan has a rudimentary baffle to keep oil from being sloshed to the front in hard stops, that's the only difference (don't know if the HD/Fleet pan is the same as police or just a standard pan). Marketing cried that a six quart oil change would make AMC engines more costly to maintain than the competition, so it was tested and found that five quarts was sufficient for normal driving, so the owners manuals state five quarts -- same as everybody else in that era.

The valley line was introduced by drag racers to help with oil starvation under hard acceleration to the rear main and rod bearings. Basically it just supplies extra volume by having another path. I think it is an aerated oil issue -- the oil gets sloshed hard enough to the rear of the pan and a lot of oil is quickly sucked up out of the pan, allowing a little air to be sucked in at the pickup. The twin paths increase the amount of oil, and should reduce aeration. I don't think it's necessary except on those really quick drag cars -- not your usual weekend bracket racer. You have to be pushing the engine near it's limits to make extreme mods like that, and I mean really built up to near max possible output. Building a 10 second or less 1/4 mile car? You might need it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel327 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/28/2019 at 6:59am
I believe someone posted pic of the 6th quart in pan.  Considering the extra volumn and the additional minimal depth of oil as it is spread about the surface area...aeration is not an issue.  The extra volumn creates no harm but instead provides several benefits.  Wish I could remember who posted pic.  I think he has built over 100 AMC V-8's..

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/28/2019 at 12:52pm
I have made all my oil pans 6 Quarts since 2012 but have not built 100's of engines.
I remove the standard pan baffle, hammer and dolly the back of the pan to an outy and not an inny and re-install the standard baffle.




Next pan to do:



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Jan/28/2019 at 1:11pm
Deja-vu ... check a few posts down for more discussion on pans & capacity.
 
Quotes from that thread posted by Steve P, an actual Engineer who worked at AMC:
 
Originally posted by Steve_P Steve_P wrote:

There is nothing about the design plan was for 6 quarts of oil in the AMC SAE papers- that's an urban legend that I think goes back to the CACI newsletter days.

The bearing clearances are wrong in the quote by LM. .0015 is way too tight for the rear main. The bearing clearances were also loosened up by AMC from the 68-70 "tight" spec, which was ~.001-.002 to a more clearance sometime around 72- which coincidentally is when AMC was selling a substantial amount police cars. The new clearance specs are what most use now, ~.002" and ~.003 on the rear main.

I have ran a pan dry at 4500-5000 RPM sustained driving and spun a #8 rod bearing. And I know others that also have. If you haven't, consider yourself lucky. With an 8+ quart pan, no more issues.
 
Originally posted by Steve_P Steve_P wrote:

There is a mention in the SAE papers for the 390 that they made a modification to the oil pan sump cover plate when the 390 was introduced- IIRC they added the drain slots on the side at that point.   

Yes, there is no issue with the AMC oil pump gear size- more than big enough, compare to a SBC. Years back someone was selling even taller gears, looking for a solution to a non-existent problem.

The problem is insufficient drain back from the heads/valve covers and has been discussed a million times. The simple solution is a bigger capacity pan.
 
X2 his post in this thread to fit an Aviaid pan or similar.  I've got an Armando pan on my 401 (very similar to the Aviaid as Armando used to work for them).
 
Hope this helps,RD
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