understanding a low oil pressure 360

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Newbomb Turk said:
Here’s an oldie but a goodie.

Before I could get an A in senior auto shop in school I was required to build an actual engine for someone who wasn’t me. There were 6 of us that had to do it. The bottom feeders in the class didn’t have to do it.

So I hooked up with a friends brother to do his 318. We had a whole list of **** we had to do to pass and that included all ring gaps, all bearing clearances, deck heights…all that.

I got the crank in, degreed the cam and didn’t measure the rod throws before hand so I said “this junk was all machined so it’ll be fine” and sent it.

I get 5-6 pistons in and I can hear a clunking as I’m turning it over. I’m thinking WTF is hit what. Didn’t see ****.

So the teacher strolls over and looks at my paperwork. He says how much rod bearing clearance do you have? I see .0025 for the mains.

Like a dickhead, I lied and said .0025 just like the mains I just didn’t write it down yet.

He looks at me funny and walks over to the garbage can, pulls out the box the rod bearings came in and said “measure it again, get it right and then head to the office”.

So I took all the junk back apart, torqued the rods back up and started checking them. Instead of the .0025 I should have had, I had .0125!

Now I’m triple pissed because the guy I paid the size the rods dicked me. I’m running around like a chicken without a head and the teacher comes over and says I didn’t take that box out of the garbage for no reason.

I’m looking at it and is says .010 under right on the box. I’m thinking WTF I’m in trouble for lying and I have no clue what’s wrong.

After about 20 minutes of nonsense from the rest of the class I decided to pull the bearings and measure them to see if they were screwed up.

Of course, I looked at the back of the bearing and it said .020 under on them. All the bearings were .020 under and every box said .010 under on them.

Hard lesson learned that day. You can’t measure enough. If it can be measured it should be measured.

My punishment for lying was I had to wash all his cars. I did 6 of them before I figured out only two were his. The other 4 belonged to other teachers.

I still got my A though.
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Auto shop classes were just cool as all heck. It's a real shame they barely exist now.
 
HOLY CRAP!! We are neighbors. We asked about your lifters because some roller lifters in some blocks can uncover the oil gallery and drop your pressure.

Did Jim build this?? If so I’d say the chances of him leaving a plug out is about 100,000:1. I can happen but it is highly unlikely he forgot a plug like that.

We are all human and can make mistakes so it may be worth looking into.
 
70 Duster Herb said:
post 12
flat tappet solid lifter forgetting cam and lift manufacturer.
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Yea we saw that, just need a little more specifics. But that’s back when we thought it might be a roller, before you said it was a solid flat. Your original post was a tad unclear as to what you thought you were running. Hey Tim, @Newbomb Turk it sounds like you should go put your hands on this thing if you’re neighbors.
 
TT5.9mag said:
Yea we saw that, just need a little more specifics. But that’s back when we thought it might be a roller, before you said it was a solid flat. Your original post was a tad unclear as to what you thought you were running. Hey Tim, @Newbomb Turk it sounds like you should go put your hands on this thing if you’re neighbors.
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That’s up to the OP.
 
How 'bout this? Any possibility that you have a block

WITH A COUPLE OF OVERSIZE LIFTER BORES?
 
The lifter gallery is a great place to bleed off oil pressure for sure....
 
Mopar Tim said:
The lifter gallery is a great place to bleed off oil pressure for sure....
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It sure is. Happened to me once. I caught it before I finished the motor. Back to Domhoff racing and bushed the bores. Something I always check now, even with flat tappets. Ya never know.....
 
70 Duster Herb said:
well since he is 80 and a world record holder at the salt flats (the engine he built) and in the hall of fame for his contributions to the racing community (Washington state) and building mopars for 60 years. maybe you can lend your knowledge to the community. otherwise moving along is a good path.
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Gets my vote.
 
70 Duster Herb said:
I don't post here much, but none of my research has produced much. Everyone always pointing to galley plugs or just random things to attempt to help.

360 rebuild
5w-20 lucas break in oil
solid lifter roller tipped adjustable rockers
new bearings fresh hot tank reassembled, 90-degree oil filter housing with WIX filter.

Running idle cold oil pressure at 10 psi
spun the oil pump with a drill pre-start up and post start up; I get 25 psi with no oil up top and when I position the cam and crank 2 separate positions both rocker shafts get 25psi. low speed on my drill, I increase speed pressure goes up.

it seems I have all plugs in and have verified all but two, not sure if 7.5 inches down the oil port on the China wall indicates no plug or if it's there, but through all I have read it's there. and behind the oil filter housing haven't looked yet, But I remember seeing one, but I'm old and have slept and drank since then.
spun pump with oil filter off (nice mess because it wasn't on purpose) and getting a lot of oil there.
Rockers are getting a lot of oil while I spin the pump manually, flows out of heads on to the headers So I'm getting oil throughout engine.

running out of possibilities.

Kind of thinking out loud here: If no plug under the 90-degree oil filter housing, should be no pressure at all.
if the pump where bad there would not be pressure or very little while spinning manually.
Best I can tell the oil, while engine running, is leaking off somehow and somewhere or not getting picked up.
I was mulling this over and I can't think of where the oil is going. only thing I can come up with is that the pump (suction side of the milling pump) is pulling air at a higher rpm than the drill is making, or the higher rpm is producing enough pressure to overcome the pressure side but before the pressure gauge, gasket. I did use the oil pump gasket and torqued to spec.

I have compared pump drive shafts and I get full engagement.
When I did start the engine, it sounded good nothing rattling or knocking or pinging.

Does anyone have a different theory? same? looking for ideas before I remove the oil pan and 90-degree oil filter housing oil pump engine and brainstem.
thanks y'all
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Oil pressure is a balance situation. The oil pump does not produce pressure, it produces flow. If you install the oil pan without the crank and cam in place you will get oil coming out of the galleries, but no pressure. The pump has a pressure relief valve that controls the maximum pressure, not the minimum.
When you install all the components, those "leaks" you noticed with no parts installed, are mostly plugged with those parts. The clearances are controlled leaks to allow fresh cool oil into the wear surface.
You have to check every bearing or journal clearance when assembling a new engine. It is almost common these days for bearings to be packaged wrong. A 0.010" US rod bearing shell on a standard journal will be tight. That same shell pair on a 0.020"US journal, will have 0.010" too much clearance. This allows oil to excessively leak out, providing low oil pressure. A high mileage engine may have main and rod bearings that are copper all the way around. Oil pressure when first started and put in Drive may be enough to keep the idiot light off, but after getting well warmed up that light will be flashing at a stop sign or red light. It is most likely no the oil.pump, but the worn bearings.
Con rod oil flow can be controlled with the bearing clearance OR the rod side clearance. In a land speed trials engine, they push the RPM limits hard. So in those engines the rod bearing clearances may be high with fairly high pressure to keep the bearing shells and journals from touching much. That would lead toscuffing the bearing and probably turning the bearing. In this case they control oil flow through the bearing by the rod side clearance. Using a tighter side clearance holds the oil in the critical bearing shell and journal. Remember these engines run at high RPM and full throttle for the better part of 5 miles, not 1/4 mile. At Bonnyville the air temperature is typically 100°F+. It will be 80°F+ at 5:30 or 6:00 AM when things get rolling. Cars that set a record speed the day before get first shot at the cool air, to possibly repeat it.
RustyRatRod said:
:rofl:
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By saying the gauge is “good” means you put a different one on and it confirms the low pressure? You can get a bore scope and look through the oil drain back in the head. To see how much “leakage” you have at the lifters, but can you really say “that is why” by looking at it? One thing that is somewhat easy and cheap is changing oil and filter. Go thicker oil, if the relief plunger is stuck open on the pump. Pressure might not change at all. Then, you could pull the pan, pump. Also plastic gauge a main and rod.
 
70 Duster Herb said:
I don't post here much, but none of my research has produced much. Everyone always pointing to galley plugs or just random things to attempt to help.

360 rebuild
5w-20 lucas break in oil
solid lifter roller tipped adjustable rockers
new bearings fresh hot tank reassembled, 90-degree oil filter housing with WIX filter.

Running idle cold oil pressure at 10 psi
spun the oil pump with a drill pre-start up and post start up; I get 25 psi with no oil up top and when I position the cam and crank 2 separate positions both rocker shafts get 25psi. low speed on my drill, I increase speed pressure goes up.

it seems I have all plugs in and have verified all but two, not sure if 7.5 inches down the oil port on the China wall indicates no plug or if it's there, but through all I have read it's there. and behind the oil filter housing haven't looked yet, But I remember seeing one, but I'm old and have slept and drank since then.
spun pump with oil filter off (nice mess because it wasn't on purpose) and getting a lot of oil there.
Rockers are getting a lot of oil while I spin the pump manually, flows out of heads on to the headers So I'm getting oil throughout engine.

running out of possibilities.

Kind of thinking out loud here: If no plug under the 90-degree oil filter housing, should be no pressure at all.
if the pump where bad there would not be pressure or very little while spinning manually.
Best I can tell the oil, while engine running, is leaking off somehow and somewhere or not getting picked up.
I was mulling this over and I can't think of where the oil is going. only thing I can come up with is that the pump (suction side of the milling pump) is pulling air at a higher rpm than the drill is making, or the higher rpm is producing enough pressure to overcome the pressure side but before the pressure gauge, gasket. I did use the oil pump gasket and torqued to spec.

I have compared pump drive shafts and I get full engagement.
When I did start the engine, it sounded good nothing rattling or knocking or pinging.

Does anyone have a different theory? same? looking for ideas before I remove the oil pan and 90-degree oil filter housing oil pump engine and brainstem.
thanks y'all
Click to expand...
Don't know if someone else has brought this up, but years ago I had the same problem on a 360. What it ended up being was the plug under the oil filter mounting plate that I wasn't aware of it was taken out at the machine shop and I didn't know about it.
 
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