Compression Check low oil pressure Now What?

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my5thmopar

my5thmopar

Life Long MOPAR Owner
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The original 318 in my 1972 Swinger has 125k miles on it. I'm the third owner BTW. The car did sit alot for the last 4 years until I just got around to driving it this year. I'm having a lot of valve noise and I'm sure this is due to low oil pressure. When the engine gets hot, at idle I have 3-4lbs oil pressure and never above 30lbs when driving. I tried 20w-50, 10-30 and 10-40 but no change. The compression readings are 135-140 on all cylinders. The car doesn't burn any oil or smoke while running. It does puff a little smoke at cold start up sometimes.

So I'm wondering if changing the oil pump will get me another few years or just cause more issues? How hard is it to change the oil pump and probably the rear main with the engine in the car?

Craig
 
you will need to remove the drag link, and raise the engine as high as possible to get the pan off..
 
Cam bearings? Any particular reason why?
Are these compression readings good bad or what for the 318?

So I'm wondering if changing the oil pump will get me another few years or just cause more issues?

Craig :scratch:
 
No promises, but consider running an engine flush followed by an oil change. Use Gunk 5 Minute Engine flush added to the oil, according to directions.

I've treated a few neglected engines with good results. Seems to do no harm, increased oil pressure in some engine, reduced oil consumption in others.
 
You can stick in a HV oil pump. Not sure if it will solve the issue, which sounds like the lower end is just worn out. But it cant hurt.
 
I appreciate the suggestions but.........I would like some explanation...........cause I don't understand why the opinions were given.

Is 135-140 low? If so what should it be...the manual says above 100psi.

Do worn cam bearings cause low oil pressure? If so can I just replace them?

What does lower end worn out mean?...Is that new bearings or a rebuild?

How about some schooling from a technical angle. Because at this point I don't know what to do. Can I fix this or should I be looking for a new engine? I see some questions getting numerous answers or are my questions just dumb? Help me out here please.

Craig
 
The comp. numbers are fine. If it were me I would remove the pan and check the rod and main bearings for excessive wear. You can check the clearance with plasigauge to get an idea of how much clearance you have.
 
Like SG said - compression numbers are great. Which means ring seal, camshaft, and valvejob are all fine. The oil pressure is low...
The cam bearings were suggested because the oil that feeds the main bearings, and then the rod bearings, goes behind the cam bearings. So if there was a worn cam bearing, the oil pressure has the possibility of bleeding some through that extra clearance.
I myself have never seen that, but I'm open to it being possible because of how the system gets oil to the crank. IMO, the mains and rods are probably just worn. You can inspect them as SG also soggested, or you can simply try to push more oil through the extra clearance. If the engine runs ok now, but the pressure is low pretty much all the time, the High Volume oil pump may make the situation bearable for a while. It's not a fix. It's a rigging job to buy some time. But, it has worked for me in the past.
Just keep asking the questions... Once a question is answered some of us tend to not keep expanding on something.
 
If you go the high volume oil pump route, you will need the MP hardened oil pump drive shaft or it is possible the stock one will twist and break under the extra load. If the car was neglected and the oil not changed frequently enough, my money is on a partially clogged oil pump pickup. Sludge can collect on the pickup screen over time and stop it up. Contrary to some popular belief, oil pressure comes from one place and one place only. The oil pump. Main, rod and camshaft bearings do have some impact on the oil pressure, but without the oil pump getting a proper flow of oil from the pickup, the flow to the rest of the engine will be low. If it was mine, I would find a good brand motor oil flush for the crankcase, follow the directions and see what happens. You might not even have to remove the oil pan.
 
Sometimes all that is needed is clean the pickup screen. You'll know when you get the pan off.
i dont believe in flushing a high milage engine. It'll flush main and rod bearings.
 
RedFish said:
Sometimes all that is needed is clean the pickup screen. You'll know when you get the pan off.
i dont believe in flushing a high milage engine. It'll flush main and rod bearings.
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Ding Ding.......First thing I'd check also :glasses7: and please don't try and flush the engine :violent1:

Rickster
 
I don't know about the no flush advice. I've done a ton of them through the years and never had one single problem. The key is making sure you get it up to temperature and leave it there long enough to break everything down good. John Balkum used to run an old school service station in Macon years ago. He would actually fill the crankcase with diesel fuel and let the engine idle for about an hour if there was sludge buildup. It worked very well.
 
StrokerScamp said:
I don't know about the no flush advice. I've done a ton of them through the years and never had one single problem. The key is making sure you get it up to temperature and leave it there long enough to break everything down good. John Balkum used to run an old school service station in Macon years ago. He would actually fill the crankcase with diesel fuel and let the engine idle for about an hour if there was sludge buildup. It worked very well.
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I'm gonna have to disagree with most of this. Flushing is always a risk. Bottom line! If there's sludge in the motor(Usually up in the heads under the valve covers) then it will end up clogging the Oil pickup. A quick check under one of the valve covers will tell the story about sludge. Pop off a valve cover and if it looks clean as a whistle under there then it's probably more of a Bearing/worn pump situation. If it's all gunked up then there's a strong chance the Pump screen is clogging up. If there's all gumk under the Valve cover then a flush will just clog up the Pump screen even more. If the screen is clogged than it's best to just change the Pump & Screen and don't disturb the sludge at all. Don't be tempted to scrape anything under the valve covers. It'll bite you in the ***.
 
That's why if it's as bad as you let on you remove the valve covers and even the intake manifold and remove the sludge by hand. Then put everything back together and flush the rest. But for a small amount of sludge buildup, there's no harm in flushing one. Disagree all you want, I've done it a lot and successfully each time.
 
StrokerScamp said:
Contrary to some popular belief, oil pressure comes from one place and one place only. The oil pump. Main, rod and camshaft bearings do have some impact on the oil pressure, but without the oil pump getting a proper flow of oil from the pickup, the flow to the rest of the engine will be low. .
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I get where you're coming from in reagrd to the OP's engine (high milage), and I agree on the intake side of the pump is critical and a problem in an engine that is filled with crap (old broken valve seals, sludge, carbon deposits, etc). I would agree that dropping the pan and replacing the pickup "might" help. But for the extra $30, I'd change the pump to an HV unit too. The drive in this type of application should be fine and I'd leave it unless and until higher rpms and heavy use will be the norm.

In terms of a mechanically healthy small block you're not even close to correct. The oil pump inlet on a small mopar IS the ultimate limiter of oil system performance, but you have to be moving a tremendous amount of oil (wide bearing clearances and sustained rpms above 7K) to even come close to the suction side being a limiter.
 
Just remember that anything flushed out and mixed with oil will get pumped thru the bearings.

BMW20oil20sludge1.jpg
 
I drop the pan once and changed all the rod bearings and 4 mains, the thrust bearing i left, a new oil pump, screen -cam, lifters and chain got me 5 good long years out of the motor before it threw a rod at 6,000

I was still in my 20's also. Today I rather pull the engine and do the work
 
StrokerScamp said:
That's why if it's as bad as you let on you remove the valve covers and even the intake manifold and remove the sludge by hand. Then put everything back together and flush the rest. But for a small amount of sludge buildup, there's no harm in flushing one. Disagree all you want, I've done it a lot and successfully each time.
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If you start disturbing all that sludge, It's gonna bite you in the *** eventually. You've just gotten lucky. We can debate all day but I've seen it first hand over & over again. We had 3 Techs in our dealership. Me Butch & another guy. Me & butch would never disturb the sludge and just carefully swapped the Pump & Screen. 100% success rate. The other guy insisted on scraping & flushing. he had a 50% success rate at best. Butch Grabinsky :prayer:is by far the best Tech I've ever known and he'll back me 100% on this. Scraping sludge = Blown engine:glasses7:
 
I would try a strat 30 or 40wt oil with an oil adative like lucus or stp..she will be good for another 100,000..........or untell you can rebuild it.....I dont think 10or 20wt. oil is enough...Artie
 
IMO I'd run that 318 til it dies. Awesome, it has good compression. Here is the real question, how much time and money do you want to spend? I wish I had kept my 318 stock instead of spending money on simple parts, wanting more, and then junk a great engine for a 360 that a bad machinist touched. I think I'll put that 318 back in. I read in a mopar engine manual that they should call an engine flush "instant rod knock." Change the oil and filter frequently if you really want to slowly desludge a motor (not if its an extreme amount of sludge), maybe use a light solvent like seafoam or hell even a little atf. Use cheap oil and change it a LOT. Be sure to monitor oil pressure more than normal. And try a different oil pressure gauge (mechanical)
 
Thanks for all the comments….The results are in. Pulled the pan and the pump screen and pan bottom were full of sludge. I’m wondering if the prior owner of 15 years ever changed the oil. But anyway. I replaced the rear main seal while I was in there…It seems to have the original rope type. I changed the pump to a HV. The tech at Melling says the stock shaft is fine with a stock engine but…never in an hp engine. The valve train noise has almost stopped completely. I need to change the leaking vc gaskets and will look around. The oil psi idiot light is on and off again. I’ll check it with my test gauge. Also the tech at Melling said I was probably wasting my time with the HV pump wont help an engine with low oil pressure. I would have to change to a high psi pump or spring but, that will cause more issues in a worn engine. BTW Melling has couple of good videos on their web site about oil volume and psi. So it seems I’ll have to rebuild or replace the engine.
Craig
 
godfatherofchry said:
I would try a strat 30 or 40wt oil with an oil adative like lucus or stp..she will be good for another 100,000..........or untell you can rebuild it.....I dont think 10or 20wt. oil is enough...Artie
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All I ask is that you please read up on what the numbers represent when discussing weights of oil. Then you will see that this won't help any engine with any problem except maybe the difference between living in an extremely cold vs extremely hot climate.
 
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