Oil pressure issues

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unapez

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I have a 360 that was completely rebuilt about 500 miles ago... It has a melling hv oil pump and stock pan. When I first started the car it had between 55-75 psi oil pressure depending on rpm. Sometimes it would drop very low 5-10 psi at idle, then come back up later.

I changed the oil (using 5w-30) after breaking in the engine and I got 0 at idle, 10 psi at 3000 rpm. I changed it again, this time using 10w-30 and got 0 at idle, 25psi at 3000 rmp. Then started hearing a mild knock so I have not started it since. I did check pressure with another gauge and it's not a faulty gauge.

A friend says it's possible that my pickup tube is too close to the pan, another says it's likely been clogged with loose silicone or crud. It sounds like the knock is coming from the front bearings. Please any help would be appreciated.
 
I hate to say it but the last time I saw that happen the bearings were ate up. Hope that is not your case but the knock is not good.
 
A knock and low oil pressure is never a good sign. Your description sounds just like the 360 that came in my Cuda. I was informed when I bought the car the engine had just been rebuilt and after I drove it about 150 miles it lost oil pressure and started knocking. I tore it down and found out they didn't re-size the rods and 5 were way out of round and it let #3 rod bearing spin.
 
IMO your options are limitied to one. Pull her down before you do any further damage to the crank and check all your bearings.

Terry
 
Recently had the same thing on a rebuilt 340, done before I bought it.
Good pressure at first start up but downhill from there.
Found sand in the oil filter, looks like parts of the block, windage tray and inside the oil pan had been sandblasted and not cleaned properly.
all rod and main bearing were shot.
Managed to get the crank ground and now it's running 65 psi hot above 1500 rpm and 35 psi idle with 10-30 with stock oil pump.
Pull it apart and hopefully you can save the crank.
 
Where/who rebuilt it? Did you see the slips for work done, or it just looked good? IMO, if the HV pump gave you low readings, you had issues from the get go. Tear it down and carefully inspect everything.
 
I brought over a friend and he drained the oil and put a screwdriver up in the pan, he says the pickup was right against the bottom of the pan... He pushed it up and we put in new oil. When it started, the oil pressure shot up to 50psi but did not stay long. It goes down to 0 at idle when warm, up to about 20 at 3000rpm. But raps anywhere above 2k.

He was looking at the oil and says it looks like there's metal in the oil, like super small metal flakes, very tiny, oil looks almost like silver paint. Most likely from not cleaning the block well after honing... I will be pulling off the pan.
 

You must have been using one heck of a set of rough stones on your hone to leave metal pieces like you described and to turn the oil silver. I might be wrong but I doubt you'll find it was a dirty block caused this. I'd bet you'll find a spun bearing. That'd explain the drop in oil pressure and knocking and trash in the oil.
 
Time for a teardown. hopefully the crank isn't too bad and it ends up being an easy fix like a missing galley plug causing low pressure. either way i would take it down to the bare block and clean the crap out it. a small amount of metal flakes left in that block could start that long downhill slope all over again. good luck.
 
You could save a lot of money pulling that engine now and tearing it down before more destruction occurs.
 
I stand by my original response, those tiny metal particles could easily be babbit from the main or rod bearings. Better find out which it is.

Terry
 
Once that starts, the domino affect mixes everything. So i'd wager it's a little bit of everything. The block will, regardless of autopsy results, need to be totally disassembled and cleaned, including oil galley plugs and passages above and below the cam bearings. And, replace the lifters or disassemble each one and clean it out. Replace the pickup and the oil pump too.
 
Could be the oil pump not seated on the main cap. Jammed oil pump relief spring

If you have significant metal flakes in the oil, tear it down and find out the reason.

I have an engine that does the same type of thing that's waiting to come out. Fires up cold with 30-40psi, hot goes to 5psi at 700 rpm, run it up to 850-900 and it jumps to 15-20. Not as bad as your situation, but, same type of thing.
 
We had one that was so dirty that while driving down the freeway the pressure dropped from 65psi at 3400RPM to 20-25psi.

I pulled of the freeway and checked what I could like sender, gauge, line, ect

Finally I decided to fk it and neutral reved it to 6000+RPM and wahlah that was enough to push all the **** past the oil pump relf spring, ran fine after that put another 3k miles on it and I still have it as a back up motor.
 
3404spdvaliant said:
Thats a no brainer there being that all the crap go's through the oil pump first.
Hope all the galley plugs were in tight too.
Click to expand...
brains is somethin i do not use too much.. LOL
but what i meant was is that the oil pump crapped out first, thus causing the rest of the damage.
"oil looking like siver paint" tells me there is a little bit more then just bearing material.
cheers.
 
For what its worth the pickup is supposed to have 1/16 to 1/8 inch interference with the pan, per the FSM.
 
66dartgt said:
For what its worth the pickup is supposed to have 1/16 to 1/8 inch interference with the pan, per the FSM.
Click to expand...

If it's a stock pickup anywhere from 1/16~1/8" is fine. The Milodon stock replacement I put in my 360 has a bar on it that holds it up about 1/4" from the bottom of the pan.

For what it's worth: In the book "How to build Mopar small block strokers" the writer mentions that Chrysler did a test way back when and found the stock pickup is restrictive and wouldn't actually flow the maximum a HV oil pump can provide so he recommends using the Milodon replacement because it flows more. I use them from now on just for safety sake. Cheap insurance I figre. JMHO
 
I dropped the pan today. (wasn't easy :angry7:) and pulled the oil pump out. I pulled off the pickup screen and ripped it open. Between the bottom cover and screen I found a silicone ball about 3/8" and maybe 3/4" long! Took the pump apart and found that the gear was scored and had a few tiny chunks of metal jammed between the inner/outer rotors. It still turns but not as smoothly as it should be. I don't see any metal shavings in the pan. :cheers:

Also, I realized that the pickup tube was about 1 1/2" from the bottom of the pan!
 
While you're under there I'd drop the main bearing caps one at a time and check for tore up bearings. You could also pull the rod caps for a look see then bolt them back up. I still think the engine needs to come out if for no other reason than a complete clean and flush of the oil channels. Oil pumps garbage also.

Terry
 
Terry's right. Pull that engine and clean all the oil gallerys. Silicone could be everywhere.
 
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