Boarder Line Low Oil Pressure

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Clelan said:
It may be temporary, but it could go for years depending how and how much the vehicle is driven.

Cley
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exactly. the low mileage original 383 in my D300 has like 12psi at idle and the second you touch the pedal it jumps to 40.

i doubt that thing sees 2K a year, 80% of that street, and i'd be shocked if it could pull 4500rpm.

am i concerned in the slightest? nope.

will i be concerned in the slightest when i pull the OG 2bbl carb and intake and snap on a 4bbl? not even remotely.
 
Dan the man said:
I agree with you. The engine does have a issue big time. Do you believe in the use of full grooved main bearings? I could've misunderstood you but I thought that earlier you said that they are a good idea and yet in post 21 your saying that they are not good for oil pressure.
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You are NOT agreeing with me Dan.

I’ll tell you exactly what I think.

No one knows what’s inside the engine. No one knows what the clearances are. Does it have full groove mains?

So how can YOU say that a 20w50 oil means the engine is junk? You can’t because you don’t know either.

Oil is cheap enough that if he changes it and the pressure is where he wants it, WTF is wrong with that? Maybe that’s what the clearances and full groove mains requires.

Doesn’t mean the engine is junk or even has an issue.

If the OP said it has half groove mains and tight clearances then you might say it’s some other issue(s) causing problems.

I highly doubt there’s a damn thing wrong with it other than full groove mains and loose clearances.

It’s been running. Hasn’t **** itself yet. If it has more than a thousand miles on it then it damn sure isn’t junk. If it was, it would already be dead.

As for full groove main bearings. If it’s a dead stock engine and the rpm will be 5500 max you can use a 1/2 groove main.

If it’s other than that it needs full groove main unless you have an R3 or Ritter block. Then you can use 1/2 groove mains.

Why are those blocks different? Because other than those blocks everything else has original Chrysler oiling and oil timing. The other blocks have priority main oiling.
 
Newbomb Turk said:
You are NOT agreeing with me Dan.

I’ll tell you exactly what I think.

No one knows what’s inside the engine. No one knows what the clearances are. Does it have full groove mains?

So how can YOU say that a 20w50 oil means the engine is junk? You can’t because you don’t know either.

Oil is cheap enough that if he changes it and the pressure is where he wants it, WTF is wrong with that? Maybe that’s what the clearances and full groove mains requires.

Doesn’t mean the engine is junk or even has an issue.

If the OP said it has half groove mains and tight clearances then you might say it’s some other issue(s) causing problems.

I highly doubt there’s a damn thing wrong with it other than full groove mains and loose clearances.

It’s been running. Hasn’t **** itself yet. If it has more than a thousand miles on it then it damn sure isn’t junk. If it was, it would already be dead.

As for full groove main bearings. If it’s a dead stock engine and the rpm will be 5500 max you can use a 1/2 groove main.

If it’s other than that it needs full groove main unless you have an R3 or Ritter block. Then you can use 1/2 groove mains.

Why are those blocks different? Because other than those blocks everything else has original Chrysler oiling and oil timing. The other blocks have priority main oiling.
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With the low oil pressure that the OP said that the engine has at idle I would've already torn into it. Back when I didn't have a lot of money to work with and I had to just put a engine together I've never had the low oil pressure that the op said that he's dealing with. It has a definite problem
 
Chasing oil pressure by changing oil grades is treating the symptom and not the cause.
 
Dan the man said:
With the low oil pressure that the OP said that the engine has at idle I would've already torn into it. Back when I didn't have a lot of money to work with and I had to just put a engine together I've never had the low oil pressure that the op said that he's dealing with. It has a definite problem
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Why Dan? Why do all that work if nothing is wrong with it.

I’m telling you and you refuse to grasp what I’m saying so I’ll try one more time.

Loose clearances and full groove mains are NOT bad or wrong. You just have to run a higher grade oil. That’s not a sin, crime or anything else.

What’s ******* crazy is you say you’d have seen the oil pressure and tear into it. I say for what?

You want to change bearings that aren’t bad? You going to tighten up all the clearances? If so you’ll need to resize the rods and line home the block.

So you’d do that BEFORE you spent 150 bucks on oil and a filter?? That’s stupid Dan. That’s why people quit this hobby.

Jumping to conclusions and then spending stupid money on stupid **** just turns people off.

Again, if the OP changes his oil and the pressure is good would you still say it’s junk and he needs to rebuild it?

Remember Dan, some engine builders build them loose to RUN 20w50 oil. That doesn’t make the engine junk.

That’s like saying that since I have to use a 0w20 oil my engine is junk. It may be junk but that’s not why it’s junk.
 
RustyRatRod said:
Chasing oil pressure by changing oil grades is treating the symptom and not the cause.
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It can be, but it doesn’t have to be. I’d call it junk if the OP knew what his clearances and bearings are then we could say for sure one way or the other.

Like I said, some builders build them
loose. Doesn’t make them junk.
 
I agree, if nothing is known about the engine or how it was assembled, we are all assuming there is a problem. If it picks up say 10psi at hot idle with 20w50 is that enough? Is it normal? Who knows. If it was my engine and it had 20w50 in it and only made 15-20psi hot at idle, I’d better see 60-70 at 5000 rpm or my junk would be coming apart for an inspection.
 
TT5.9mag said:
I agree, if nothing is known about the engine or how it was assembled, we are all assuming there is a problem. If it picks up say 10psi at hot idle with 20w50 is that enough? Is it normal? Who knows. If it was my engine and it had 20w50 in it and only made 15-20psi hot at idle, I’d better see 60-70 at 5000 rpm or my junk would be coming apart for an inspection.
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Assuming anything without more info is incorrect.
 
Check the block serial number for oversized lifter bore, if cam and lifters were replaced I went thru this problem once ,had to have lifter bore bushing in one hole
 
the op made no mention of the motor having been rebuilt. neither he or the previous owner know any of the internal clearances. this tells me it hasn't been apart for quite some time. so any assumptions about a bad rebuild are just guessing and off topic. as some have said change the filter and swap to 20/50 before touching anything else. it could well just be a higher mileage motor that's getting a bit loose in it's old age and needs servicing accordingly, lol.
neil.
 
My son and I rebuilt my 340 several years ago and oil pressure was fine, but a few months later the pressure started dropping, I thought oh **** what did I screw up. I tried 20w50, no help so I was going to tear down the engine luckily, I dropped the trans and pulled the torque convertor and noticed oil weeping from the cam plug I cleaned around the perimeter, got out the JB Weld and problem solved and have great pressure ever since. Goes to show, you never know until you start poking around!
 
Not everyone has the funds or the ability to tear into a motor.
With all the unknowns about this motor, and the fact it has been running this way for years, plus a hot climate in the summer.
Do what it takes to get a more comfortable oil pressure and enjoy it.

Everything is “only temporary” anyway.
EVERYTHING.
 
TrailBeast said:
Everything is “only temporary” anyway.
EVERYTHING.
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when i was a line monkey at a fleet shop the guy in the stall next to mine had a saying: it's only temporary till it ain't

which i kinda chalked up to the break neck pace and the keep it cheap and get it done mentality over everything else. it wasn't until years later i truly grasped the subtle nuance of the line.
 
I had a professor in college say in our engine rebuilding class, to run the thinnest oil the engine wants.
This is comming from a guy who raced AC cobras when they were new.
 
Mcfarlrm said:
Appreciate the recommendation. I'm not aware of the clearances nor did the previous owner have this info. Oil pressure has always been this way since the day I purchased it a couple years ago. Do I need to add a zinc additive to these? I currently run Lucas Hot Rod with high zinc.
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The zinc is for the flat tappet cam and lifters.
Low hot oil pressure at idle indicates to me that bearing clearances could be a bit excessive. I would remove the oil pan to plastigage the main and rod clearances.
When you are checking the mains, you have to support the crank as the weight will cause a lower clearance indication than actually present. My method is to use a piece of cereal box cardboard in #3 and just snug those main bolts enough to hold the crank up. Then plastigage the other 4. Then put cardboard in #2 and #4 mains to check #3. This is not needed on the con rod bearings. If the journals are std and the clearance is a bit high, you can install 0.001US bearings to tighten it up.
If the crank has been ground US, it is possible the wrong size bearings were installed. New bearings can be carefully rolled in with the crank and rods inframe.
 
junkyardhero said:
sounds like the bearings are jusssstttt on the loose side of things and she's opening up a little when she gets hot and dropping some pressure.

i'll echo what others have said up thread and suggest going with a thicker oil and see what that yields.

if you still have less than thrilling pressure after that (and checking your gauge) then it may be time to rethink things.
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"Things" do not "open up" when the engine gets warmed to operating temperature. Oil pumps are rarely the issue either, although the Buick V6 did have a bit of a problem with the outside mounted pumps. The oil path was convoluted.
The pressure drop is caused by the oil thinning out as it gets well warmed up.
I repaired a number of Ford pickups with 400 engines. The Clevelland design engines are known for not having the best lubrication systems, and the 400 was based on the Clevelland. At about 100k miles the OP indicator light would start to flicker when stopped in Drive at red lights or stop signs. The farm boys would come in and ask if I could install a new oil pump. I would pull the oil pan and clean and inspect the oil pump, and never found much for wear. Witness marks, yes. Check the main and rod bearings and they would show copper on the top and bottom shells. I then checked the timing chain which with that mileage was worn. I then phoned and explained what I found and a price for replacing the bearings and timing set. Always installed a double roller timing chain. I also installed 0.001"US bearings to take make up for the journal wear. This usually brought the clearances close to the minimum spec. A couple of guys were upset I did not replace the oil pump. I told them to drive it for a week or two and if they were not happy, I would do the labor at no cost if they paid for the pump. None came back for a new pump.
Bearing clearance is a "leak". When the oil is cold it does not leak out the clearances as readily, so oil pressure looks fairly good. As the oil gets well warmed up, it leaks out easier, causing a pressure drop. If the clearances are on the high side with warm oil, more leaks out and the pressure drops. As you rev it up the pump pushes a lot more oil volume, so the pressure improves.
 
Dan the man said:
I agree with you. The engine does have a issue big time. Do you believe in the use of full grooved main bearings? I could've misunderstood you but I thought that earlier you said that they are a good idea and yet in post 21 your saying that they are not good for oil pressure.
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Full grooved main bearings are an attempt to provide more consistent oil flow to the rod bearings. Similar is/was cross drilled crankshafts. The problem with fully grooved main bearings is the reduced surface area. Similar is cutting a groove in the main journal, recommended for the old Chev sixes. Abetter option than full grooved is 3/4 grooved.
 
Dan the man said:
That's a good idea but I think that it's only a temporary fix. Like mentioned earlier a plug or something could've not been put in or came loose. It could be a bearing clearance issue or a bad oil pump and possibly the lifter bores could have excess clearance. I don't mean to sound negative here or anything but I think that your not to far from having to take it apart and see what's going on. True, the thicker oil will help for a while but if it's a clearance issue or the pump is bad it will only get worse over time.
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Dan before talking out your *** at least do some research. You beat It to death that you always know better since you base all your post on past research.
Go look at oil charts. Driven has one.
 
Dan the man said:
I agree with you. The engine does have a issue big time. Do you believe in the use of full grooved main bearings? I could've misunderstood you but I thought that earlier you said that they are a good idea and yet in post 21 your saying that they are not good for oil pressure.
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How do you know? You do know "Some Engines" are built loose right?
It may have been built for thicker oils.
Sending a sample out would also be on the list when you swap to a heavier oil.
The report will tell you a lot.
 
fishmens67 said:
This is debatable.
I can't remember the last time I ran a full groove.
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My opinion is the engines we use still have a jacked up oiling system.

It didn’t get fixed until the R3 and Ritter blocks.

So any engine making any power and shifting at 6000 or higher should have them. Over 8000 you have to do other stuff to make them live.

There is no reason not to run them. I do not now nor have I never believed that you give up too much bearing area.

I’ve never seen a main bearing fail from lack of load bearing area.
 
340six said:
How do you know? You do know "Some Engines" are built loose right?
It may have been built for thicker oils.
Sending a sample out would also be on the list when you swap to a heavier oil.
The report will tell you a lot.
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Look through an older Chilton's manual. Like the big pink book we called it. I think it's like 65 to 72. Somethin like that. I have one somewhere. Compare ALL the other us makes bearing Clearances to Ford. Ford had consistently greater bearing clearances than all the rest. Also, if you've ever been around an older original Ford with any of those old engines from the past that had some mileage on them, you can hear them rattle. Perfectly normal for them. They just ran and ran and ran and ran.
 
Newbomb Turk said:
My opinion is the engines we use still have a jacked up oiling system.

It didn’t get fixed until the R3 and Ritter blocks.

So any engine making any power and shifting at 6000 or higher should have them. Over 8000 you have to do other stuff to make them live.

There is no reason not to run them. I do not now nor have I never believed that you give up too much bearing area.

I’ve never seen a main bearing fail from lack of load bearing area.
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I agree. You could even argue that the oiling systems on some of them were almost an afterthought.
 
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