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Discussion Starter · #1 ·
I just installed a temp. mech. oil press. gauge using a industrial type gauge. There's no deference between this and an automotive gauge, except it's ugly....
Cold eng. I'm pushing nearly 80 psi, warm about 70 psi, and as hot as I've been able to get so far about 48 psi at idle. This is great, but seems high for a SB (318 in this case). Just wondering if anyone can think of something that could cause excessive high press.. or should I just be happy !
When I got this truck it had about 20 k on a rebuilt engine. It starts and runs great, good compression etc. I'm starting to get some lifter noise, so I'm thinking this was a regular 'back yard' rebuild, rings, bearings etc., but reused cam, lifters, rockers etc.
Oh and the 'new gauge' agrees with hi - low thing on the factory gauge.
Any thoughts....
 

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Discussion Starter · #3 ·
ramchargerrunner360 said:
well i wish u could be happy but there is a oil sending unit on the dodge that is famous for going out i would replace that and see what u get
I understand - except this is a mechanical gauge, 'teed' off the main port, before the stock electrical sending unit....
 

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book says you are supposed to be running between 30-80 psi of oil pressure. so i dont think i would be to concerend about it

eric
 

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In my 318, after 3 hours of highway travel at 65-70 mph (2000-2200 rpm in OD) I run around 55-60 psi. When I stop and idle in drive, I've got 20-25.

In my 360 (before I started parting the truck out--it's on a stand now) I had around 60 psi at 65 mph (3k rpm...3 spd) and idled around 20 psi in gear.
 
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Quick rule of thumb is 10 lbs per thousand rpm's. Any more than that is a waste of power. Granted, you can't have a pump increase in such a linear pattern, but you could drop a step in oil weight and see if it's more reasonable.....or be happy where you are and hope that pressure doesn't blow a gasket out.
 

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Discussion Starter · #8 ·
Ok - Thanks all - I thought this was Ok on the high side. Just wanted to check.
The first engine I ever rebuilt @ 17, I installed the pressure relef valve wrong, and got 200 + psi of oil pressure !! , this has been a 'thing ' of mine ever since (being concerned about too high of oil pressure.


Edit: fix dumb statement.....
 

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Your oil pressure is on the tad high side. More then likely they used a HV oil pump in the rebuild. Everytime i've ever used a HV pump in a SB Mopar i got 80-100 psi. I don't ever use HV pumps in SB anymore because oiling has never been an issue with them and the HV pumps are just foaming and heating up the oil. So what i would do is run 5w-30 oil if your using 10W now or go to 10w30 if your using 30 w now.
 

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Discussion Starter · #10 ·
Thanks 300le - I think you may be on to something. I don't really know what was done to the engine, and was wondering if they had screwed up the pressure relief some how. But if your right about the oil foaming thing, this could explain the lifter noise - it's not a normal 'sharp metalic tic' but more of a mushy (for lack of a better word) sound. I'll change the oil this weekend and try your tip - will let you know....
 

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my motor has some crazy tolerances or something, because if i try to run anything thicker than 10W-30, the pressure skyrockets, to the point that it will blow out the seal around the oil filter plate. but once i dropped down, it works great.

Jake
 

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DDGRC84 said:
my motor has some crazy tolerances or something, because if i try to run anything thicker than 10W-30, the pressure skyrockets, to the point that it will blow out the seal around the oil filter plate. but once i dropped down, it works great.

Jake
If it skyrockets, it may be that the pressure relief valve isn't opening up all the way, or at some point somebody has changed or shimmed up the spring in the pressure relief valve. If the spring has been modified, my guess is that you would probably get normal oil pressure at hot idle and then it would continue to climb as RPM increases.....probably starting to exceed 80psi at around 3 grand.
 

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Discussion Starter · #13 ·
Ok, first, thanks for your comments all. I changed the oil to 5-30. Cold it still pushes 80 psi, warm 30 - 40 at idle (depending on engine temp), about 65 psi at 65 mph (don't have a tach right now). So this is more like it should be.
Odd thing is, the valve train noise is about 70 percent better, but still there, I would have thought that it would stay the same or go away ??? Anyway I'm back to pulling the pan, and intake to see whats going on in there.
Any other comments - Thanks
 

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If your dropping the oil pan, change the oil pump to a normal oil pump. I'm pretty sure you have a HV unit. Then you can use the 10w-30 oil again.
 

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Discussion Starter · #15 ·
chrysler300le said:
If your dropping the oil pan, change the oil pump to a normal oil pump. I'm pretty sure you have a HV unit. Then you can use the 10w-30 oil again.
Yeah - thats why I'm dropping the pan.
 

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Let us know what the outcome is.
 

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K.C. said:
DDGRC84 said:
my motor has some crazy tolerances or something, because if i try to run anything thicker than 10W-30, the pressure skyrockets, to the point that it will blow out the seal around the oil filter plate. but once i dropped down, it works great.

Jake
If it skyrockets, it may be that the pressure relief valve isn't opening up all the way, or at some point somebody has changed or shimmed up the spring in the pressure relief valve. If the spring has been modified, my guess is that you would probably get normal oil pressure at hot idle and then it would continue to climb as RPM increases.....probably starting to exceed 80psi at around 3 grand.
nope, at the time it had a brand new oil pump, and the motor was less than three weeks off a rebuild i did myself. i started with 15W-40, and it was 80+ at warm idle. now, once i switched to 10W-30, it sits at 25psi warm idle, and rises to around 70psi as i approach redline.

Jake
 

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sorry for a newbie question, but what´s the problem with high oil pressure ??? provides cool and enough oil for everything to come...


someone once told me that V8s sometimes use to drop oil pressure below critical point when idling after a ride at full throttle...that´s why i´m confused :/
 

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Well, too high oil pressure (over 90 to 100+ pounds) could wash out the surface of the main and rod bearings back in the old days, I don't know if that applies to modern bearings or not.

And as Jake pointed out, it makes it harder for the oil filter gasket to stay seated.

What I'm trying to figure out is the valve train noise change with lower viscosity/lower pressure/higher oil flow rate.
300le, do you know if there is a design limit on the SB valve train operating oil pressure?
 

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Not sure what the design limit on the valve train would be but i'm sure if there was enough pressure the lifters could overcome the valve springs and not let the valves fully seat.

The reason too much oil pressure is bad is that it is a parasitic waste on power and fuel mileage. Could lose an easy 10 hp if not more by running 100 psi when only 50 was needed. Since usually the oil passages aren't opened up when a HV oil pump is installed the oiling system can't handle the extra flow and then the oil is just pressurized more. Oil under pressure generates heat. Just grab ahold of some hydraulic lines of some machinery that runs at about 2000-2500 psi. After awhile you could easily burn yourself with how hot the lines get. Same goes for motor oil that is unnessarily pressurized it will generate heat and break down sooner. Non synthetic motor oil starts to break down around 180 degrees which is what it normally runs at in a normal engine. If the oil was pressurized more it could run 20-50 degrees hotter making it break down even faster. Engines that have super high oil pressure need thier oil changed more frequently. I have also seen on one engine with a HV oil pump and Full groove bearings with loose clearences use some oil. The reason is excessive oil was being forced out around the rod and main bearings and being slung up on the cylinder walls like normal, but there was an excessive amount. The oil rings couldnt' control it all so it used about a quart of oil every 1000-1500 miles or so. A crank scraper would of solved this though.
 
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