No oil pressure

[Sailwood]

Gang,

Just rebuilt. Essentially new rings, main and rod bearings on newly turned and polished crank, 110 hrs on OEM cam, lifters, keepers, tappets; new idler bush and shaft, rebuilt accessory drive and reversing bearings; cylinders honed (in spec); valve guides and cam bearings in spec; new head,; deck flat. You name it. All in a lifelong fresh water cooled block. Ran great on engine test stand. Run to 180 4 times and re-torqued. Has plunger style oil pressure adjuster with seat dressed before oil added with fine shavings magnetically removed. OP was 30# on testing with 20# after warm-up that drifted down to 12#. Now near zero. Removed plunger and spring which looked good. Stewart-Warner OP guage. Putting mechanical guage in to compare. Adjustment stem screwed in a bit at a time from almost all the way out to fully seated. Highest OP was about 10#. Any clues as to what to do? I'm fearing a total breakdown to have a look but REALLY want some easier if not better direction.

Doug Soden

[lat 64]

At first glance, it looks like too much clearance in main bearings. That's just a first reaction, not a top choice.

To begin the interrogation, were the crank main and rod bearings plastigaged or checked for sure during assembly? Your symptoms were the same as my engine before I tore it apart. It turned out the last "mechanic" to assemble my engine had used standard main bearings on a reground undersized crank.
After my engine warmed up the oil pressure just bled off at the main bearings because they were so sloppy. Amazingly no damage occurred. Can you confirm the mains and rods were the right undersizesd for the reground crank?

Same theory applies to cam bearings too


Some guys here have forgotten some little oil gallery plug during assembly that resulted in low or no oil pressure. You have some, so I doubt that is your issue.



Cheers,
Russ

[romantic comedy]

Russ, that was my first thoughts also. But if he had Op then now has none?

[Sony2000]

To maximize OP I turned the set screw in until two threads were sticking out of the block. Just enough to securely hold the cap in place. To get a higher pressure from there, it takes thicker oil.

[tenders]

Does the oil itself look OK - hasn't been diluted by gas or water? OP gauge wiring and ground are all OK?

[Mo]

I'd be really concerned about bearing mismatch. As guys have pointed out, ensure it's not a gauge problem. I don't know when / or if my engine was rebuilt. I've used it for 5 years and have 40 psi on start up and don't even drop all the way back to 30 once warmed up. I would think a new rebuild should be offering you somewhere around the same as that.

If the gauge checks out I think you may need to pull it apart and see what is up.

[Sailwood]

Crank was turned 10 under , has 10 over new bearings. The first start-up produced, briefly, 60# pressure that quickly bled off. All oil galley plugs are in. Even though the op valve seat was dressed, I'm wondering about some crud getting in there. Yes, the block was cleaned. As stated, the cam bearings were miced (sp?).

Doug

[tenders]

Originally Posted by Maurice

I've used it for 5 years and have 40 psi on start up and don't even drop all the way back to 30 once warmed up.

FWIW, this is my experience too, 18 years after rebuild.

[lat 64]

Originally Posted by Sailwood

... The first start-up produced, briefly, 60# pressure that quickly bled off. ...
Doug

That's a good clue.
It just might be more crud like you say.

I have only seen a couple of mis-boxed bearing shells over the last 25 years, but that is why I always mic every journal on the crank and plastiguage under every shell as I assemble an engine(not too often these days)
That being said, I don't think that's the problem.

[hanleyclifford]

Sounds like something is preventing the cone from seating. Probably something from upstream in the screen or gallery in the bearing cap. A picture right down the tube would be revealing but I know that could be difficult.

[Sailwood]

The decision has been made to pull the engine and completely break it down. It's the only way to feel comfortable. I'll have the oil pump checked out at Moyer Marine although I have doubts that that is the problem.

Question: I understand that the main journals are machined (line bored) for a specific block when manufactured. Would/could main blocks inadvertantly switched during re-build possibly be the culprit? Not from front to back which can't happen, but from old block to replacement block? All journals will be checked again as well as cam bearings. Even though the machine shop re-ground the crank 10 under and 10 over bearings were installed, I can't rule out the possibility of a mis-match somehow.

So what is a plastiguage? By that question I obviously did not ude one.

Doug

[romantic comedy]

Plastic gauge is cool little strips of plastic that you check clearances with. You use it for main bearing and rod bearings. You get the correct plstic gauge based on the clearance specs. Then you cut a strip off and put it across the crank journal. You assemble the bearing and torque it to specs. DONT rotate the bearing at all.

The plastic gauge squeezes to take up the space between the journal and the bearing.

Now you take it apart, without rotating it. You will see the plastic gauge on the journal bearing surface. The package is marked with marks representing the thickness that the plastic has spread to. You just find the corresponding width, and it tells you the clearance. Pretty simple concept. keep a pack with you at all times.

[ILikeRust]

Originally Posted by lat 64

Some guys here have forgotten some little oil gallery plug during assembly that resulted in low or no oil pressure.

Get the hell out! How could anyone be so negligent and sloppy as to do something as bone-headed as that?

P.S. - it results not in "low" oil pressure, but NO oil pressure. DAMHIKT.

[Dave Neptune]

Doug, sorry to chime in so late but you are on the right path!! I doubt the mis-matched bearing as it is rare and most are stamped so they can be "read". You had som OP on initial start up and you did state you "kissed" the relief vallve seat, hopefully you did get all of the chips out. That leads me to a problem I have encountered only once on a friends ole 426 wedge Mopar motor. He had it bored and the crank reground new cam bearings installed by the rebuilder and he assembled the rest as soon as he got the parts home. He finished the rebuild and fired it up. She sounded good and all reading were good! So out for a drive he went, it was a short drive as he leaned on it a bit after about 5 miles the OP went up and he spun some bearings and we towed it back. The problem turned out to be loose debris not cleaned out of the oil galleys and the delivery to the crank was comprimised causing much damage. Just from a skipped step~cleaning the oil galleys~and being in a hurry~tough lesson!!!
If it was a plug it was installed but not tight and you may find it laying around if indeed that is the issue. Other than a plugged galley I have seen the pickup screen get plugged and even fall off as he bolts were not tightened.

Dave Neptune
Did you get a chance to check with a mechanical gage?

Dave Neptune

[Sailwood]

Scary thought, Dave. That was a passing thought but blew it off as "so unlikely" as the block was reportedly cleaned. My memory now tells me that the oil plugs were NOT removed. I checked and counted them on rebuild so I know they are there. If the "missing oil galley plug" notion was a dumb ass move (now who said that?), not cleaning passages on a complete, otherwise (I think) meticulous rebuild is about one nanometer off taking the lead. We'll see. I'm a little burned out at this point so will re-charge my batteries and then tow Aspen over to the yard, pull the engine and tear it down.

Doug

[joe_db]

I had a Lycoming sheer the gear teeth off of the oil pump
Oil was fine one minute and 0 PSI the next.

[lat 64]

Originally Posted by Sailwood

The decision has been made to pull the engine and completely break it down. It's the only way to feel comfortable. I'll have the oil pump checked out at Moyer Marine although I have doubts that that is the problem.

Question: I understand that the main journals are machined (line bored) for a specific block when manufactured. Would/could main blocks inadvertantly switched during re-build possibly be the culprit? Not from front to back which can't happen, but from old block to replacement block? All journals will be checked again as well as cam bearings. Even though the machine shop re-ground the crank 10 under and 10 over bearings were installed, I can't rule out the possibility of a mis-match somehow.

So what is a plastiguage? By that question I obviously did not ude one.

Doug

Doug,
Can you take lots of high-res photos as you tear it down? Every little step. Some amazing things have been caught on"film" by me and others.
I wish you could rule out a bad oil-relief-valve seat before you tear it down though, So much work!

Russ