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Oil Pressure Temporarily Drops On Acceleration

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JGRANTAMX View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote JGRANTAMX Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 5:36pm
 An easy test would be add another quart of oil and see if it helps, some say a stock AMC pan can hold 6 quarts without issues maybe you can run 8 quarts.

J


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 7:28pm
Originally posted by JGRANTAMX JGRANTAMX wrote:

 An easy test would be add another quart of oil and see if it helps, some say a stock AMC pan can hold 6 quarts without issues maybe you can run 8 quarts.

J





Tried that too. No change. Starting to wonder if this has always been happening but I simply never noticed. Also wondering if a stock type pan baffle in the Canton pan would be helpful.

-Steve-



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Post Options Post Options   Thanks (0) Thanks(0)   Quote bwamx Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2022 at 8:17pm
Which Canton pan is that? What pickup is used? I have a Canton deep sump but with an external pickup. 
Are there trapdoors on those baffles?  My pan has no baffling down low. I don’t have any pics but seem to remember a shelf like the stock pan at the rear of the sump. I can’t see how you could be draining the  pan on such a short rpm blip. I’ll run the 1/4 in a rpm range of 6500-7400  the whole time. No pressure drop or drain back issues. What weight oil and filter and in stock location?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jmerican Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 11:41am
Modern sticky tires? Big rubber? G-forces can be really strong these days, in a straight line or round a corner. Trick Wet sump vehicles will often exceed gravity. ( like a hot air balloon, jk ) Maybe canton came up short with the rear baffle. You mentioned supercharged, which probably adds a bit of let’s say surge under the rolling stomp you speak of. 

As others have offered, try a bump in oil level. That is easy. Sure windage blah blah, but really, your issue seems less likely to be windage or drainback. It’s an instantaneous thing, and those above mentioned things would take more steady state operation to occur. 

The oil will stack up at 45 degrees under your anti gravity launch. (@1G) and with the car lifting the front a bit, and the sudden surge, you can bet that oil slams aft and then sloshes. All while drawing serious gulps of oil from the pickup, creating a vortex that may exceed the sloped slug of oil. 

To me, the baffle you show in your pic seems inadequate, IMO.

The idea of moving the pickup aft as suggested, to me, may also be a good idea, but more difficult. Maybe canton could do better there too. Possible. 

I do think it’s possible that your relief spring is weak, and may not recover quickly once you blow it off a bit with a quick rap.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Midnight Rambler Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 1:17pm
Originally posted by JGRANTAMX JGRANTAMX wrote:

 An easy test would be add another quart of oil and see if it helps, some say a stock AMC pan can hold 6 quarts without issues maybe you can run 8 quarts.

J




That was my thought.  I know there are a few common sticks with different full lines on them.  If the pan is 8qts, I'd do an oil change with 8 qts and put a new "full" indicator on the stick.  It would seem most likely to be that or the baffle.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 4:29pm
Originally posted by bwamx bwamx wrote:

Which Canton pan is that? What pickup is used? I have a Canton deep sump but with an external pickup. 
Are there trapdoors on those baffles?  My pan has no baffling down low. I don’t have any pics but seem to remember a shelf like the stock pan at the rear of the sump. I can’t see how you could be draining the  pan on such a short rpm blip. I’ll run the 1/4 in a rpm range of 6500-7400  the whole time. No pressure drop or drain back issues. What weight oil and filter and in stock location?



This is the Canton pan: https://www.jegs.com/i/Canton-Racing-Products/074/15-554/10002/-1

Using their pickup tube: https://www.jegs.com/i/Canton-Racing-Products/074/15-555/10002/-1

I believe it has spring loaded trapdoors. 10W-30 oil. Purolator filter in the stock location.

-Steve-
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 4:40pm
You stated 7 quarts to the full mark. The pan advertisement states 8 quart and 9 quarts with filter.
Are the 7 quarts with or without the filter?
They built the pan and doubt they would mislead on how much oil the pan holds installed on an AMC V8.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 4:41pm
Originally posted by Jmerican Jmerican wrote:

Modern sticky tires? Big rubber? G-forces can be really strong these days, in a straight line or round a corner. Trick Wet sump vehicles will often exceed gravity. ( like a hot air balloon, jk ) Maybe canton came up short with the rear baffle. You mentioned supercharged, which probably adds a bit of let’s say surge under the rolling stomp you speak of. 

As others have offered, try a bump in oil level. That is easy. Sure windage blah blah, but really, your issue seems less likely to be windage or drainback. It’s an instantaneous thing, and those above mentioned things would take more steady state operation to occur. 

The oil will stack up at 45 degrees under your anti gravity launch. (@1G) and with the car lifting the front a bit, and the sudden surge, you can bet that oil slams aft and then sloshes. All while drawing serious gulps of oil from the pickup, creating a vortex that may exceed the sloped slug of oil. 

To me, the baffle you show in your pic seems inadequate, IMO.

The idea of moving the pickup aft as suggested, to me, may also be a good idea, but more difficult. Maybe canton could do better there too. Possible. 

I do think it’s possible that your relief spring is weak, and may not recover quickly once you blow it off a bit with a quick rap.




Running sticky Mickey Thompson rubber, car hooks pretty good even on the street. It'll pull the front wheels and inch or so on a prepped surface.

Tried the extra quart of oil, no change.

Think I'm just gonna run it. If I hear a rod knocking I'll tear it down.

-Steve-

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 4:46pm
When I first got the Canton pan I put water in it a quart at a time to check the level.


Four quarts:





Five quarts:





Six quarts:





Seven quarts:





Eight quarts:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: May/16/2022 at 5:38pm
Don't forget that the filter is about 1/2 quart and there is a decent amount of oil in circulation while the engine is running.  I read a thread here that the oil level drops at least 1 quart while the engine is running (this was to help justify running 6 quarts in a stock pan).

So you may be running at the 6 quart level in your pictures.

I think its good that several people have indicated not to worry about it.

Mike
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